POLYMER BLENDS AND PROCESSING PROGRAM

Applications of polymer blends and multiphase polymer materials continue to enjoy growth in terms of market share, consumption, and employment within the plastics industry. This growth challenges the flexibility of materials suppliers to meet customer needs with new materials and reduced product development cycles. The futility of trial and error approaches to address these challenges led industry to solicit measurement tools and methods of analysis which enhance their efforts to understand and control resin compatibility, phase morphology, and material properties. These demands have been further sharpened by the advent of new methods which provide better control in polymer synthesis and more precise definition of material components.

The Polymer Blends and Processing Program began with clear scientific goals to establish expertise in static and kinetic aspects of phase behavior in polymer blends, effects of shear flow on mixing and separating, and reactive processing to promote compatibility. The focus on these areas furthers program objectives by accelerating development of new measurement tools, including specialized light and neutron scattering methods, and by applying those tools to expand the knowledge base for thermodynamics and kinetics of polymer blends. Work extends to the effects of additives in a blend system, the relative behavior of blends in bulk compared to in thin films at interfaces, and the effects of complex thermal and mechanical histories on the phase separation. Fundamental advances in theory and modeling continue to guide and interpret the measurements.

Current research in the program has four areas of emphasis: (1) measurement technology for on-line characterization of temperature, phase behavior, and shear deformation; (2) shear effects on phase diagrams and phase morphology; (3) activity of additives, compatibilizers, and fillers; and (4) control of interfacial effects in blends and during processing. In each of these areas the program works with industry tement methods using tools of fluorescence, light scattering, neutron scattering and reflectivity, x-ray scattering, birefringence, microscopy (AFM, TEM, phase contrast), and rheology. Industrial collaborators include: Aristech Chemical, Dendritech, DSM, Dow Chemical, Dow Corning, DuPont, Dynisco, Exxon, Kodak, GE, Goodyear, Mobil, Raychem, Rohm and Haas, and 3M.

In order to promote communication and technology transfer with an even broader range of industrial partners the Polymer Blends and Processing Center has been established. The focus of the Center is efficient adoption of measurement technologies developed at NIST and assessment of new research directions for the Polymer Blends and Processing Program. The Center also promotes initiatives which cut across research projects to improve opportunities for industrial collaborators to use NIST measurement capabilities.

Significant Accomplishments

The capability of NIST-developed on-line instrumentation, using light scattering and optical microscopy to measure in-situ domain size and shape during extrusion of incompatible and reactively compatibilized blends was demonstrated. In addition to morphology studies, the instrumentation can measure velocity profiles and characterize multiphase mixing. Industrial partners including 3M and Rohm & Haas have begun work using this instrument to investigate effects of polymer processing aids.

NIST's on-line microscopy extruder instrument has revealed new droplet morphologies in the high shear stress regime which are tentatively attributed to normal forces. For two component systems, with a high viscosity ratio, droplets with negative surface curvature or structures elongated orthogonal to the flow direction, were observed. This result demonstrates the power of on-line measurements to complement typical post processing studies.

In collaboration with Packard Electric, the determination of specific changes in the spectrum of a fluorescent probe provided simultaneous measurement of temperature and crosslinking in a polyethylene/polyvinyl acetate copolymer. This measurement can be used to control and monitor continuous extrusion of wire insulation during which crosslinking is activated by raising the temperature in the later stages of processing. During the early stages of the extrusion, limited crosslinking is allowed so that the rheology remains uniform.

Dendrimer molecules of divergent types have been characterized with a combination of small angle neutron scattering, small angle x-ray scattering, and transmission electron microscopy. Four critical observations arise from the solution characterization which contrast dendrimers with other classes of polymers: Dendrimers are spherical in shape and have a narrow size distribution even at relatively low molecular mass; the segment density distribution profile is nearly uniform within the dendrimer; the terminal units of the dendrimer are located within a relatively narrow shell toward the periphery of the molecule; and with increasing concentration the dendrimers appear to collapse and pack in a random close packing arrangement with little interpenetration. These characteristics suggest possible applications as size and molecular mass calibration standards for SANS, SAXS, TEM, AFM, MALDI, SEC, and filtration.

Measurements on thin film blends have established that nucleation and growth at the late stage of phase separation is dominated by a coalescence mechanism rather than by Ostwald ripening. Studies by bulk scattering techniques are not able to distinguish between coalescence mechanisms and Ostwald ripening because the time dependence is identical.

A combination of time resolved light scattering and video microscopy together with transmission electron microscopy was used to observe the influence of block copolymer additives on phase separation kinetics and morphology development. A new compatibilization mechanism via the break-up of discrete domains in the late stage of spinodal decomposition was seen. We believe that this mechanism is responsible for some of the properties of compatibilized polymer blends which could now be tailored by process design.

In collaboration with Exxon, large pressure induced demixing in metallocene polyolefin blends was demonstrated through optical cloud point measurements. The observed linear dependence of the demixing temperature on pressure is 0.24 /C/MPa. High pressures are typical in most polymer processing, including polyolefins, and the strong dependence on pressure will greatly shift phase boundaries.

Dynamic and steady shear viscoelastic properties of elastomer blends were correlated with the domain structure observed in shear mixing experiments with light scattering and optical microscopy. These correlations provide understanding and guidance for elastomer mixing and milling processes.

The equilibrium and non-equilibrium phase behavior of a series of blends containing varying amounts of hydrogen bonding components were studied by small angle neutron scattering. Results can be explained by a two length scale model, with a thermal fluctuation length and a chemical barrier length due to the hydrogen bonding. This system has a fractal microstructure during phase separation and consequently should exhibit low or zero shrinkage.

NIST hosted a three day joint scientific workshop with the Hashimoto Phasing Project of the Exploratory Research and Technology Organization (ERATO) of Japan, which was attended by over 65 representatives of U.S. industry, ERATO, and NIST. In addition to further developing the scientific interactions between these two research groups, the workshop provided U.S. industrial researchers a direct view of the ERATO-supported project.

 

Phase Behavior and Pair Interaction Parameters in Polymer Blends

C. C. Han, S. Kim¹, H. Jeon², C. Jackson, J. F. Douglas, B. Lee and S. Glotzer
¹University of Wisconsin, Madison, Wisconsin
²Polytechnic University, Brooklyn, New York

Objectives
The objectives are to develop techniques and methods to characterize phase behavior and interaction parameters of polymer blends and to provide measurements and data in support of other activities of the program.

Technical Description
Characterize the flow effect on multi-phase polymer blends at high shear rates and study the relationship between viscoelastic response of the phase morphology and the flow instability or the possibility of re-entrant of phase separation at higher shear rate.

Investigate the influence of block copolymer additives on the phase stability and kinetics of phase separation by correlating time dependent light scattering and video microscopy results.

Study effects of copolymer additives on the static phase diagrams and on the enhanced composition fluctuations.

External Collaborators
R. Stadler, University of Bayreuth, Bayreuth, Germany - Collaboration and supply of polycaprolactone (PCL) and PCL block polymers.

Accomplishments

• A combination of time resolved light scattering and video microscopy together with transmission electron microscopy was used to observe the influence of block copolymer additives on phase separation kinetics and morphology development. A new compatibilization mechanism via the break-up of discrete domains in the late stage of spinodal decomposition was seen. We believe that this mechanism is responsible for some of the properties of compatibilized polymer blends which could now be tailored by process design.
• At fixed molecular mass of copolymer additives, the temperature dependence of thermodynamic properties, such as susceptibility and correlation length, becomes weaker (or smaller) as copolymer concentration increases. Also, deviation from mean-field scaling behavior (for a typical binary polymer blend) becomes greater.

Outputs

Publications

C.L. Jackson, L. Sung and C.C. Han, Evolution of Phase Morphology in Compatibilized Polymer Blends at Constant Quench Depths: Complementary Studies by Light Scattering and Transmission Electron Microscopy, Polymer Engineering and Science, 37, 1, (1997).

C.L. Jackson, L. Sung and C.C. Han, Morphology and Phase Separation Kinetics of a Compatibilized Blend, Society of Plastics Engineers, ANTEC Proceedings, 1, 1559 (1996).

L. Sung, D.B. Hess, C.L. Jackson and C.C. Han, Phase Separation Kinetics and Morphology in a Polymer Blend with Diblock Copolymer Additive, J. Polym Research (Taiwan), 3, 139 (1996).

C.L. Jackson, H.D. Chanzy, C.C. Han, V. Balsamo, F. von Glydenfeldt and R. Stadler, Surface Topology and Organization of Single Crystals from Polystyrene- Polycaprolactone (PS-b-PCL) and PS-Polybutadiene-PCL (PS-b-PB-b-PCL) Block Copolymers, American Chemical Society PMSE Preprints, 77, 660 (1997).

S.A. Langer and S.C. Glotzer, Morphogenesis in Liquid Crystal/Polymer Blends: Theory and Simulation, CPIP >96 Conf. Proceedings, Pattern Formation in Fluids and Materials, Physica A, in press.

S.C. Glotzer and S.A. Langer, Morphogenesis in Liquid Crystal/Polymer Blends, Proc. from International Conference on Pattern Formation in Polymers, in press.

Presentations

S.C. Glotzer and S.A. Langer, Modeling Phase Separation in Anisotropic Polymer Blends, Canadian Applied Math Society Workshop on Industrial and Applied Math, Toronto, Canada, June 1997.

S.A. Langer and S.C. Glotzer, Modeling Anisotropic Polymer Blends, Society for Industrial and Applied Mathematics Conference on Computational Materials Science, Philadelphia, May 1997.

L. Sung, J. Holoubek and C.C. Han, Phase Separation and Dissolution in Binary Blends with Addition of Diblock Copolymers: Light Scattering and Image Analysis Studies, Symposium on ASurface and Interfacial Phenomena in Macromolecular Systems,@ Prague, Czech Republic, July 1997.

C.L. Jackson, L. Sung and C.C. Han, Morphology Evolution and Phase Separation Kinetics in a Polymer Blend with Diblock Copolymer Additive, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

C.C. Han, J.-W. Yu, S. Kim, E.K. Hobbie and J.F. Douglas, Homogenization of Polymer Blends by Shear Flow, American Physical Society March Meeting, Kansas City, MO, March 1997.

C.C. Han, From Phase Diagram Characterization to Polymer Blends Processing: Statics, Kinetics and Influence of Flow Field, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

C.L. Jackson, Surface Topology and Organization of Single Crystals from Polystyrene- Polycaprolactone (PS-b-PCL) and PS-Polybutadiene-PCL (PS-b-PB-b-PCL) Block Copolymers, American Chemical Society, Las Vegas, NV, September 1997.

Structure Formation by Shear in Polymer Blends

C. C. Han, S. Kim¹, J.-W. Yu¹, H. Jeon², D. Johnsonbaugh; A. I. Nakatani, E. K. Hobbie³ and J. F. Douglas
¹University of Wisconsin, Madison, Wisconsin
²Polytechnic University, Brooklyn, New York
³University of Pennsylvania, Philadelphia, Pennsylvania

Objective
The objective is to develop the framework for controlling polymer blend morphology as a function of shear rate and compatibilizer concentration and, working in collaboration with industry, demonstrate application of characterization methods to determine parameters for specific systems.

Technical Description

Determine the compatibilization effect on polymer blends by the corresponding block copolymers under shear flow by the small angle neutron scattering measurement.

Characterize the structure change of polymer blends by combined time resolved light scattering and video microscopy techniques.

Investigate the shear mixing, structural change and flow instability of polymer blends which possess a strong elastic effect.

External Collaborators

- Exxon Research and Eng. Co. - Collaboration and supply of polyolefins for shear mixing and morphology studies.

- Goodyear Rubber and Tire Co. - Collaboration and supply of polybutadienes and polyisoprenes of various microstructure for the elastomer blend study.

- Nagoya University - Examination of shear behavior of block copolymer solutions by SANS.

- Kyoto Institute of Technology - Examination of phase behavior of labeled polystyrene/poly(vinyl methyl ether) blends as a function of the isomeric state of the label.

Accomplishments

Shear induced mixing of low vinyl polybutadiene/low vinyl polyisoprene LCST blends (LPB/LPI) and low vinyl polybutadiene/high vinyl polyisoprene UCST (LPB/HPI) blends demonstrates a change of droplet aspect ratio as a function of shear rate. This change was related to a shift of the phase diagram.

Dynamic and steady shear viscoelastic properties of elastomer blends were correlated with the domain structure observed in shear mixing experiments with light scattering and optical microscopy. These correlations provide understanding and guidance for elastomer mixing and milling processes.

The relationship between the structural change of two-phase elastomer blends under shear (droplet deformation, breaking, elongation, homogenization and instability) was compared and correlated with the corresponding steady state and dynamic rheological properties.

SANS experiments on two types of samples, PSD/PB/PSD-PB and PSH/PB/PSD-PB, were performed as a function of shear rate, temperature and copolymer concentration. It has been shown that copolymers act to enhance miscibility, at low concentrations of copolymer, with and without the application of shear. Above a certain copolymer concentration, the copolymer destabilizes the single phase region during shear. In the quiescent state, the miscible region is expanded compared to the blend without copolymer.

Outputs

Publications

A.I. Nakatani and C.C. Han, Shear Dependence of the Equilibrium and Kinetic Behavior of Multicomponent Systems in AStructure and Properties of Multi-Phase Polymeric Materials,@ T. Araki, M. Shibayama and Q. Tran-Cong, eds., Marcel Dekker Inc., New York, 1997.

Y. Takahashi, S. Kitade, N. Ochiai, I. Noda, Y. Matsushita, M. Imai, A.I. Nakatani, H. Kim and C.C. Han, Order-Disorder Transition of Symmetric Styrene-2-Vinylpyridine Diblock Copolymers in Melts and Solutions, Polymer Journal (Japan), submitted.

S. Kitade, N. Ochiai, Y. Takahashi., I. Noda, Y. Matsushita, A. Karim, A.I. Nakatani and C.C. Han, Lamellar Orientation of Diblock Copolymer Solutions Under Steady Shear Flow, Macromolecules, submitted.

A.I. Nakatani, L. Sung, E.K. Hobbie and C.C. Han, Shear-Induced Order in a Homopolymer Blend with Block Copolymer Surfactant, Phys. Rev. Lett., submitted.

L. Sung, A.I. Nakatani, C.C. Han, A. Karim, J.F. Douglas and S.K. Satija, The Role of Copolymer Additive on Phase Behavior of a Polymer Blend, Physica B, submitted.

J.-W. Yu, J.F. Douglas, E.K. Hobbie, S.K. Kim and C.C. Han, Shear-Induced AHomogenization@ of a Diluted Polymer Blend, Phys. Rev. Lett., 78, 2664 (1997).

S. Kim, E.K. Hobbie, J.-W. Yu and C.C. Han, Droplet Breakup and Shear-Induced Mixing in Critical Polymer Blends, Macromolecules, submitted.

S. Kim, E.K. Hobbie, J.-W. Yu and C.C. Han, Pattern Formation and Scaling in Critical Polymer Mixtures Under Simple Shear Flow, Proceedings of International Conference on the Morphology and Kinetics of Phase Separating Complex Fluids, Messina, Italy (to be published in Il Nuovo Cimento D).

Presentations

A.I. Nakatani, Phase Behavior of Compatibilized Blends During Shear, University of Wisconsin, Department of Chemistry, November 1996.

A.I. Nakatani, SANS of Compatibilized Blends During Shear, Gordon Research Conference Polymers (West), Ventura, CA, January 1997.

A.I. Nakatani, SANS of Compatibilized Polymer Blends During Shear, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

A.I. Nakatani, Small Angle Neutron Scattering of Polymer Blends Under Shear, NIST- ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

S. Kim, E.K. Hobbie, J.-W. Yu and C.C. Han, Droplet Breakup and Shear-Induced Mixing in Critical Polymer Blends, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

E.K. Hobbie, Pattern Formation And Scaling in Critical Polymer Mixtures Under Simple Shear Flow, Dept. of Physics, University of Pennsylvania, October 1996.

C.C. Han, Homogenization and Critical Temperature Shift of Polymer Blends Under Shear Flow, Materials Research Society, San Francisco, CA, April 1997.

C.C. Han, Morphology of Two-Phase Polymer Mixture Under Shear Flow, NIST Workshop on Characterization and Modeling of the Polymer/Polymer Interface/ Interphase Region, June 1997.

C.C. Han, S. Kim, E.K. Hobbie, J.-W. Yu, Pattern Formation and Scaling in Critical Polymer Mixtures Under Simple Shear Flow, International Conference on The Morphology and Kinetics of Phase Separating Complex Fluids, Messina, Italy, June 1997.

C.C. Han, S. Kim, E.K. Hobbie, J.-W. Yu, Pattern Formation Polymer Mixtures Under Simple Shear Flow, Thirteenth Symposium on Thermophysical Properties, NIST, Boulder, CO, June 1997.

C.C. Han, Morphology of Two Phase Blends Under Shear Flow, Gordon Research Conference on Elastomers, Networks and Gels, July 1997.

C.C. Han, Critical Scaling and Pattern Formation of Polymer Blends Under Shear Flow, International Workshop on Structure and Dynamics of Complex Fluids Under Shear Flow, Max-Planck-Institute for Polymer Research, Mainz, Germany, September 1997.

On-Line Morphological Characterization of Polymer Blends

K. Migler, E. Hobbie¹, B. Bauer, D.-W. Liu, D. Johnsonbaugh, C. Han and E. Amis
¹University of Pennsylvania, Philadelphia, Pennsylvania

Objective
The objective is to demonstrate effectiveness of light scattering and phase contrast microscopy measurements of polymer blend morphology and flow profiles for on-line characterization of processing in a slit-die extruder.

Technical Description

An extrusion slit die with optical access for in-situ microscopy and light scattering enables measurement of polymer blend morphology and polymer flow profiles.

Optical microscopy permits measurements of structures in the 2 :m to 200 :m range while light scattering can measure structures at length scales down to 0.1 :m.

Identify key processing variables in the control of material structure. Examine the influence of processing on the development of morphology for representative classes of polymer blends.

Demonstrate the ability to measure polymer flow profiles across the slit die using particle tracing microscopy.

Measure real time changes in domain size during reactive extrusion.

Measure the effects of strong shear stress on domain shape and size.

External Collaborations

- 3M - velocity profile measurements with polymer processing additives
- Rohm & Haas - velocity profile measurements with polymer processing additives
- Exxon Research and Engineering Co. - morphology of polyolefin blends during extrusion

Accomplishments

The capability of NIST-developed on-line instrumentation, using light scattering and optical microscopy to measure in-situ domain size and shape during extrusion of incompatible and reactively compatibilized blends was demonstrated. In addition to morphology studies, the instrumentation can measure velocity profiles and characterize multiphase mixing. Industrial partners including 3M and Rohm & Haas have begun work using this instrument to investigate effects of polymer processing aids.

Direct measurement of flow profiles in a slit die during extrusion, including transition from Poiseuille flow to plug flow, as a function of mass flow.

Light scattering measurements during reactive extrusion show dramatic reduction in domain size and ellipticity due to decrease of blend interfacial tension.

NIST's on-line microscopy extruder instrument has revealed new droplet morphologies in the high shear stress regime which are tentatively attributed to normal forces. For two component systems, with a high viscosity ratio, droplets with negative surface curvature or structures elongated orthogonal to the flow direction, were observed. This result demonstrates the power of on-line measurements to complement typical post processing studies.

Direct observation of coarsening in dilute uncompatibilized blend following cessation of flow during extrusion.

In-situ measurement of the dramatic change in domain size and elongation as a function of distance to the wall utilizing light scattering in conjunction with a purge - feed technique. Correlation of this effect with independently measured flow profile, provides a physical understanding of the skin-core effect.

Outputs

Publications

S. Li, K.B. Migler, E.K. Hobbie, H. Kramer, C.C. Han and E.J. Amis, Light Scattering Photometer with Optical Microscope for In-line Study of Polymer Blends Extrusion, J. Polym. Sci.: Polym. Phys. Ed., in press.

E.K. Hobbie, K.B. Migler, C.C. Han and E.J. Amis, Light Scattering and Optical Microscopy as in-line Probes of Polymer Blend Extrusion, Advances in Polymer Technology, in press.

Presentations

E.K. Hobbie, Morphology of Two-Phase Channel Flow in Extruded Polymer Blends, American Physical Society, March Meeting, Kansas City, MO, March 1997.

K.B. Migler, Light Scattering Photometer with Optical Microscope for In-line study of Polymer Blends Extrusion, Polymer Processing Society 13 (PPS 13) June 1997.

E.K. Hobbie, Droplet Coalescence and Coarsening in Extruded Polymer Blends, 71^st American Chemical Society Colloid and Surface Science Symposium, University of Delaware, July 1997.

E.K. Hobbie, Light Scattering/Microscopy Characterization of Polymer Blends in a Twin Screw Extruder, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

B.J. Bauer, Compatibilizers Made From Copolymers that Exhibit Strong Interactions, AIChE Meeting, Chicago, IL, November 1996.

B.J. Bauer, Compatibilizers Made from Copolymers that have Strong Specific Interactions, Materials Research Society Meeting, Boston, MA, November 1996.

Fluorescence Monitoring of Polymer Processing

A. Bur, K. Migler, S. Roth, J. Gruber and E. Amis

Objectives

The objectives are to develop sensors based on optical and fluorescence measuring techniques for monitoring important polymer processing parameters, such as temperature, temperature gradients, pressure, strain rate and molecular orientation and to develop models describing sensor behavior.

Technical Description

Methods use fluorescent dyes which exhibit changes in their spectrum with temperature and pressure and which orient with applied stress.

Dye spectra are analyzed using statistical methods in order to establish correlations with temperature and pressure and to support model descriptions of dye behavior.

Sensors are designed to fit into standard instrument ports in processing machines.

A temperature profile sensor employs confocal optics in order to isolate the point of measurement and yields a temperature profile by scanning the point of focus through the resin.

A fluorescence anisotropy sensor containing polarizing optics is used to measure molecular orientation.

Ultrasonic sensors are also being developed to complement the fluorescence measurements and are used to monitor temperature and resin modulus during extrusion and injection molding.

An optical sensor for injection molding is used to monitor crystallization kinetics by measuring light transmission through the crystallizing resin.

Applications of these sensors include the measurement of temperature profiles during resin extrusion, measurement of molecular orientation in stretched films, kinetics of resin crystallization and glass formation during injection molding and measurements of machine residence time during extrusion.

External Collaborations

- DuPont - measurements of temperature profiles during extrusion.
- Mobil Chemical - measurement of molecular orientation during biaxial stretching of polypropylene films.
- DELPHI Packard Electric - measurement of temperature and crosslinking during the extrusion of polyethylene wire insulation.
- General Electric - measurement of temperature and resin solidification kinetics during injection molding.
- 3M Co. - measurement of residence time profiles during extrusion using the confocal optics sensor.
- University of Utah - development of high temperature ultrasonics transducers for extrusion and the application of fluorescence confocal temperature measurements during injection molding.

NIST Information Technology Laboratory - analysis of fluorescence spectra using statistical methods to identify correlations with temperature and pressure and to develop models describing dye behavior.

Accomplishments

Demonstrated the feasibility of measuring strain rate by the method of fluorescence recovery after photobleaching.

Employed the polarizing optics sensor to measure fluorescence anisotropy in films of polypropylene doped with a fluorescent dye and to scan over the surface of large area films to measure anisotropy as a function of position.

Developed a model to describe light transmission through crystallizing polypropylene during injection molding.

In collaboration with Packard Electric, the determination of specific changes in the spectrum of a fluorescent probe provided simultaneous measurement of temperature and crosslinking in a polyethylene/polyvinyl acetate copolymer. This measurement can be used to control and monitor continuous extrusion of wire insulation during which crosslinking is activated by raising the temperature in the later stages of processing. During the early stages of the extrusion, limited crosslinking is allowed so that the rheology remains uniform.

A patent was awarded for the confocal optics sensor for temperature profile measurements.

Impact
The technology developed in this project is being used by 3M Co., Mobil Chemical Co. and DELPHI Packard Electric in R&D studies of polymer processing. This technology is the subject of ongoing collaborations with 3M Co., DuPont Co., DELPHI Packard Electric, Mobil Chemical Co. and General Electric. 3M Co. is employing our technology to adjust the process parameters based on measurements of residence time in process machines. Mobil Chemical Co. is using fluorescence anisotropy as a measure of orientation in biaxially stretched polypropylene films. DELPHI Packard Electric is using fluorescent dyes to obtain temperature and crosslinking data for wire insulation. General Electric is collaborating with NIST in order to study resin crystallization kinetics and resin shrinkage during injection molding. These companies have sought NIST technology because existing process monitoring methods are inadequate.

Outputs

Publications

A.J. Bur and C.L. Thomas, Optical and Ultrasonic Techniques for Monitoring Polymer Manufacturing Processes, Chapter in book edited by George Birnbaum, Published by the American Society For Non-Destructive Testing, 1997.

A.J. Bur and C.L. Thomas, Optical Monitoring of Polypropylene Injection Molding, Proc. Society of Plastics Engineers Ann. Tech. Mtg., Toronto, Canada, May 1997.

K.B. Migler and A.J. Bur, Measurement of Temperature Profiles During Polymer Processing, Proc. Society of Plastics Engineers Ann. Tech. Mtg., Toronto, Canada, May 1997.

K.B. Migler and A.J. Bur, Measurement of Temperature Profiles During Polymer Processing, Plastics Engineering, October, 1997.

K.B. Migler and A.J. Bur, Fluorescence Based Measurement of Temperature Profiles During Polymer Processing, Polym. Eng. Sci., in press.

A.J. Bur, M.G. Vangel, S.C. Roth and D.S. Johnsonbaugh, Real-Time Resin Temperature Measurements from Fluorescence Spectroscopy, Proi. and Eng., Las Vegas, NV, September 1997.

A.J. Bur, K.B. Migler, M.G. Vangel and D.S. Johnsonbaugh, Real-Time Temperature Measurements for Polymer Processing Using Fluorescence Spectroscopy, Proc. ASME Mtg., Dallas, TX, November 1997.

Presentations

A.J. Bur, Optical and Ultrasonics Sensors for Polymer Processing, Federal Laboratories Consortium for Technology Transfer Annual Meeting, East Brunswick, NJ, March 1997.

A.J. Bur and C.L. Thomas, Optical Monitoring of Polypropylene Injection Molding, Society of Plastics Engineers Ann. Tech. Mtg., Toronto, Canada, May 1997.

K.B. Migler and A.J. Bur, Measurement of Temperature Profiles During Polymer Processing, Society of Plastics Engineers Ann. Tech. Mtg., Toronto, Canada, May 1997.

K.B. Migler and A.J. Bur, Measurement of Temperature Profiles During Polymer Processing, Polym. Processing Soc. Mtg. 13, Hoboken, NJ, June 1997.

A.J. Bur, Fluorescence Based Temperature and Crosslinking Measurements of Wire Insulation, DELPHI Packard Electric, Warren, OH, June 1997.

A.J. Bur, Fluorescence and Optical Monitoring of Polymer Injection Molding, General Electric Co., Schenectady, NY, July 1997.

A.J. Bur, M.G. Vangel, S.C. Roth and D.S. Johnsonbaugh, Real-Time Resin Temperature Measurements from Fluorescence Spectroscopy, Am. Chem. Soc. Mtg. Polym. Materials Sci. and Eng. Div., Las Vegas, NV, September 1997.

Interfacial Interactions in Multi-Phase Systems

A. Karim, B. Bauer, H. Jeon¹, J. Douglas, D. Liu, B. Ermi² and E. Amis
¹Polytechnic University, Brooklyn, New York
²University of Southern California, Los Angeles, California

Objective
The objective is to characterize interfacial interaction parameters necessary to control and stabilize dispersions in a polymer matrix of particles, polymer droplet phases and dendritic molecules for thin film coatings and in bulk.

Technical Description

Investigate frustrated coalescence phenomena in chemically reactive blend films.

Compare interdiffusion promoted by chemical reaction in reactive blends with thermally diffusive mechanisms in non-reactive blends.

Measure interfacial broadening in strongly interacting polymer/random copolymer bilayers and compare with theoretical predictions. Determine miscibility window for wide composition range of random copolymer.

Characterize layer formation and determine control conditions necessary for preparing uniform and reproducible dendrimer monolayer films.

Study surface properties of dendrimers and dendrigraft/polymer bilayers utilizing atomic force microscopy (AFM), X-ray reflectivity (XR), neutron reflectivity (NR) and optical microscopy (OM).

Investigate compatibilization effects of added block and graft copolymer on the morphology and kinetics of phase separation in thin polymer blend films using AFM, OM and NR.

External Collaborations

- Dr. Dusty Majumdar, GE Plastics - Research collaboration including preparation of deuterated materials and joint research on strong interactions between polymer pairs.

- Dr. Donald Paul and Glen Merfeld, U. Texas, Austin - Research collaboration on unique materials with a graduate student working part-time at NIST .

- Raychem Corporation - Joint feasibility tests of in-situ AFM on phase separating polymer blend films with surfactant additives.

- Dendritech - Supply of materials for thin film dendrimer studies.

Accomplishments

Copolymer composition study establishes that interfacial widths in bilayers of deuterated polyphenylene oxide (dPPO)/styrene (acrylonitrile (AN) or maleic anhydride (MA)) follow theoretically predicted trends as function of comoposition. However, the detailed shape of profile is asymmetric about bilayer interface, rather than prediced symmetric shape.

Neutron reflectivity was used to determine bilayer interface thickness and shape. The interfaces are substantially thicker than estiamated theoretically, and in addition, have an asymmetric shape about the joining boundary. This is expected to affect fracture toughness and adhesion strength.

Uniform spin coated monolayer films of PAMAM dendrimers from generations 3 to 6 were prepared and characterized by XR and AFM. A film collapse transition was observed in films from generation 6 through 10.

Wetting of polyethyloxazoline dendrigraft thin films yield novel patterns for higher branching content dendrigrafts that resemble floral shapes. These have not been observed previously in dewetting of linear polymers, possibly due to difference in entanglement behavior.

Discovered that blend films of low molecular mass poly(styrene/butadiene) were stabilized by segregation of high molecular mass diblock copolymers to film boundaries, preventing lateral phase separation. Only transient stability was observed for small diblocks in a high molecular mass matrix.

Demonstrated suppression of coalescence in polystyrene/polyvinylmethylether (PS/PVME) blend films by surfactant additives.

Outputs

Publications

N. Torikai, I. Noda, A. Karim, S.K. Satija, C.C. Han, Y. Matsushita and T. Kawakatsu, Neutron Reflection Studies on Segment Distribution of Block Chains in Lamellar Microphase-Separated Structures, Macromolecules, 30, 2907 (1997).

A. Karim, J.F. Douglas, S.K. Satija, A.P.Y. Wong and C.C. Han, Phase Separation in Chemically Reactive Polymer Films, Macromolecules, submitted.

A. Karim, D.W. Liu, B.J. Bauer, J.F. Douglas and E.J. Amis, Influence of Generation Number on the Formation of Dendrimer Monolayers, American Chemical Society PMSE Proceedings, 77, 181 (1997).

J.F. Douglas, H. Scheider, P. Frantz, R. Lipman and S. Granick, Origin and Characterization of Conformational Heterogeneity in Adsorbed Polymer Layers, J. Cond. Matter, 9, 7699 (1997).

J.F. Douglas, R. Lipman, A. Karim and S. Granick, Models of the Influence of Excluded Volume on the Formation of Polymer Layers, American Chemical Society PMSE Proceedings, 77, 644 (1997).

L. Sung, A.I. Nakatani, C.C. Han, A. Karim, J.F. Douglas and S.K. Satija, The Role of Copolymer Additives on the Phase Behavior of a Polymer Blend, Physica B, in press.

Presentations

D. Majumdar, Interface Development in Strong Interaction dPPO/SAN Systems, Company Presentation, GE Plastics, Selkirk, New York, May 1997.

J.F. Douglas, R. Lipman, A. Karim and S. Granick, Models of the Influence of Excluded Volume on the Formation of Polymer Layers, American Chemical Society, Las Vegas, NV, September 1997.

A. Karim, D.W. Liu, B.J. Bauer, J.F. Douglas, E.J. Amis and D.A. Tomalia, Influence of Generation Number on the Formation of Dendrimer Films, American Chemical Society, Las Vegas, NV, September 1997.

L. Sung, A.I. Nakatani, C.C. Han, A. Karim, J.F. Douglas and S. K. Satija, The Role of Copolymer Additive on the Phase Behavior of a Polymer Blend, Reactor Division, NIST, Gaithersburg, MD, September 1996.

L. Sung, A.I. Nakatani, C.C. Han, A. Karim, J.F. Douglas and S.K. Satija, Influence of Copolymer Additive on the Phase Behavior of a Polymer Blend, International Conference on Neutron Scattering (ICNS), Toronto, Canada, August 1997.

L. Sung, A. Karim , C.C. Han, J.F. Douglas and S.K. Satija, Influence of Copolymer Additive on the Phase Behavior of a Polymer Blend, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

A. Karim, J.F. Douglas, L. Sung and S.K. Satija, Determination of Structure of Thin Polymer Blend Films with Diblock Copolymer Additives, American Crystallography Association, St. Louis, MO, July 1997.

H.S. Jeon, J.-W. Yu, A.I. Nakatani and C.C. Han, Microstructure Effects on Morphology in Critical PB/PI Mixtures under Shear Flow, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

L. Sung, S.K. Satija, A. Karim, J.F. Douglas and C.C. Han, Modification of Blend Film Pattern Formation with Block Copolymer Additives, American Physical Society March Meeting, Kansas City, MO, March, 1997.

A. Karim, Phase Separation induced Roughening in Thin Polymer Blend Films, Workshop on APolymer-Polymer Interfaces and Interphases@ organized by BFRL, NIST, June 1997.

Stabilization of Blends by Strong Interactions

C. C. Han, C. Zhou¹, H. Gruell², C. Gettinger, B. Bauer, A. Karim, R. Xie³, E. K. Hobbie⁴, F. Ikkai⁵ and J. F. Douglas
¹Fudan University, Shanghai, China
²Alexander von Humboldt Foundation, Germany
³University of Connecticut, Storrs, Connecticut
⁴University of Pennsylvania, Philadelphia, Pennsylvania
⁵Kyoto Institute of Technology, Kyoto, Japan

Objectives
The objectives are to measure the effects of strong interactions, including hydrogen bonding and metal ion complexation, on the phase behavior of polymer blends in bulk and surfaces and to explore applications of compatibilizers based on strong interactions.

Technical Description

Study the wettability of silicon oxide substrates by polymers with a combination of X-ray reflectivity, optical and atomic force microscopies.

Sulfonated polystyrene ionomers (SPS) with varying sulfonation level and different metal counterions are used to control wetting and the patterns formed during de-wetting.

End labeled polystyrene, PS-eOH and polybutylmethacrylate, PBMA-eOH are used together to study the influence of symmetry, thickness and hydrogen bonding effects on the phase separation and roughening of thin films on a silicon substrate.

Hydrogen bonding is used to control miscibility, the structure of the phase separated polymer blends and also surface wetting.

The influence of cross-linking density, temperature and degree of ionization on structural inhomogeneities in a weakly charged gel consisting of (N-isopropylacrylamide-co-acrylic acid) (NIPA-AAc) copolymers is studied by SANS and the results are analyzed by recent theories.

Investigate the influence of cross-linking density on structural inhomogeneities in an ion-exchange resin having sulfonic acid groups and compare results with measurements on precursor polymers. Study the kinetics of microstructure development in NIPA-AAc gels after discrete temperature jumps through the critical point.

External Collaborations

- Bob Weiss, University of Connecticut - Collaboration and supply sulfonated polymers with various counterions.

- Kyoto Institute of Technology - Collaboration to prepare NIPA-AAc copolymer gels.

Accomplishments

The wettability of low molecular mass sulfonated polystyrene ionomers (PS, M_w=4,000 g/mol) (SPS) with various levels of functionalization and metal counterion (Li⁺, Zn²⁺) on inorganic silicon oxide substrates has been characterized by using a combination of x-ray reflectivity, optical and atomic force microscopy measurements.

It was shown that inter and intra molecular complexation, in addition to long range electrostatic polymer-surface interactions, are important in retarding the dewetting process.

A slowing down with increasing film thickness of the phase separation kinetics has been observed by x-ray reflectivity and AFM for a hydrogen bonding blend on a silicon surface covered with polymer grafts.

The equilibrium and non-equilibrium phase behavior of a series of blends containing varying amounts of hydrogen bonding components were studied by small angle neutron scattering. Results can be explained by a two length scale model, with a thermal fluctuation length and a chemical barrier length due to the hydrogen bonding. This system has a fractal microstructure during phase separation and consequently should exhibit low or zero shrinkage.

Structure inhomogeneity as a function of crosslinking density was evaluated for a series of charged polymer gels as a function of crosslinking conditions, temperature, and charge density.

Outputs

Publications

F. Ikkai, M. Shibayama, S. Nomura and C.C. Han, Complexation of Poly(vinyl alcohol)-Congo Red Aqueous Solutions, 3. Dynamic Light Scattering Study, J. Polym. Sci. B, Polym. Phys., 34, 939 (1996).

M. Shibayama, F. Ikkai, S. Inamoto, S. Nomura and C.C. Han, pH and Salt Concentration Dependence of the Microstructure of Poly(N-isopropylacrylamide-co- acrylic acid) gels, J. Chem. Phys., 105, 4358 (1996).

N. Torikai, I. Noda, A. Karim, S.K. Satija, C.C. Han, Y. Matsushita and T. Kawakatsu, Neutron Reflection Studies on Segment Distribution of Block Chains in Lamellar Microphase-Separated Structures, Macromolecules, 30, 2907 (1997).

Y. Feng, A. Karim, R.A. Weiss, J.F. Douglas and C.C. Han, Modification of the Wettability of Polystyrene Films Through Sulfonation and Metal Complexation, Macromolecules, submitted.

E.K. Hobbie, G. Merkle, B.J. Bauer, and C.C. Han, Spinodal Decomposition in Hydrogen-Bonded Polymer Blends, Modern Phys. Lett. B, 10, 1219 (1996).

C. Zhou, E.K. Hobbie, B.J. Bauer, L. Sung, M. Jiang and C.C. Han, Control of Interaction Strength in Hydrogen-Bonded Polymer Blends via the Density of the Hydroxyl Group, Macromolecules, submitted.

Presentations

F. Ikkai, Effect of Degree of Cross-linking on Spatial Inhomogeneity in Polymer Gels, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

B.J. Bauer, Compatibilizers Made from Copolymers that Exhibit Strong Interactions, AIChE Meeting, Chicago, IL, November 1996.

B.J. Bauer, Compatibilizers Made from Copolymers that Have Strong Specific Interactions, Materials Research Society Meeting, Boston, MA, November 1996.

C.L. Zhou, E. K.Hobbie, B.J. Bauer, L. Sung, M. Jiang and C.C. Han, NIST- ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes,@ June 1997.

Pattern Formation by Polymer Blends in Coatings and Adhesive Layers

A. Karim, B. Ermi¹, H. Gruell², J. Douglas, B. Lee, S. Glotzer, D. Liu, E. Amis and C. Han
¹University of Southern California, Los Angeles, California
²Alexander von Humboldt Foundation, Germany

Objectives
The objectives are to develop techniques and methodology for controlling surface adhesion, wetting, and pattern formation in polymer films through phase separation, layer thickness, and surface reaction.

Technical Description

Investigate theoretical and experimental aspects of finite size effects on phase separation of fluid mixtures with particular emphasis on the influence of surface interactions.

Experimentally characterize the effect of reduced dimensionality on the growth of pattern size and morphology type in thin film blends phase separation.

Directly observe pattern formation and measure kinetics of pattern formation in real space in off-critical blend films.

Demonstrate capacity to control surface pattern formation in phase separating blends through surface templates which vary the surface interaction.

Determine how characteristic pattern size, chemical nature, and geometry of substrate boundaries affect detailed local geometry of phase separating mixtures.

External Collaborations

- Harvard U. - collaboration to prepare chemically patterned self assembled monolayer (SAM) substrates.

- Penn State U. and U. Maryland - collaboration on SANS of thin blend films.

- Exxon Chemicals - collaboration on and synthesis of chemically end-functionalized deuterated polymers.

- Goodyear Tire Company - materials supplied for phase separation studies.

Accomplishments

Kinetics of phase separation was characterized in off-critical composition PS/PVME blend films.

Measurements on thin film blends have established that nucleation and growth at the late stage of phase separation is dominated by a coalescence mechanism rather than by Ostwald ripening. Studies by bulk scattering techniques are not able to distinguish between coalescence mechanisms and Ostwald ripening because the time dependence is identical.

Dissolution of phase separated surface structures demonstrated the thermodynamic reversibility of confined phase separated structures.

Demonstrated alignment and healing of substrates pattern defects in phase separating thin blend films deposited on chemically patterned striped substrates.

Aligned phase separated blends were shown to stabilize through control of substrate patterning dimensions. Existence of upper limit on chemical pattern length scale necessary for blend alignment was determined.

Simulations of fluid phase separation in 2 and 3-D with a variety of patterned and regular surfaces demonstrated the development of checkerboard morphology.

Confirmed trapping of an unfavorable solvent layer by a polymer brush from an off-critical binary solvent mixture due to presence of an attractive wall.

Measured surface segregation in thin PS/PVME and PS/PB blend films. Surface compositions approach bulk two phase co-existing compositions as predicted theoretically.

 

Outputs

Publications

A. Karim, J.F. Douglas, L. Sung, B.D. Ermi, Demixing of Polymer Blends in Ultrathin Films, Physics News in 1996 published by American Institute of Physics; APS News, Vol. 6, May 1997.

A. Karim, T.M. Slawecki, S.K. Kumar, J.F. Douglas, C.C. Han, T.P. Russell and M. Rafailovich, Phase Separation in Symmetrically Segregating Thin Polymer Blend Films, Macromolecules, submitted.

B.D. Ermi, A. Karim, J.F. Douglas, Formation and Dissolution of Phase-Separated Structures in Ultrathin Blend Films, J. Polym. Sci., Polym. Phys., in press.

S.K. Kumar, J.F. Douglas, I. Szliefer and T.P. Russell, How Thick is a Thin Polymer Film, Phys. Rev. Lett., submitted.

A. Karim, J.F. Douglas, J.A. Rogers, R.A. Jackman, E.J. Amis and G.M. Whitesides, Phase Separation of Ultrathin Polymer Blend Films on Chemically Patterned SAM Substrates, Phys. Rev. Lett., submitted.

S.K. Satija, P.D. Gallagher, A. Karim and L.J. Fetters, End-Grafted Polystyrene Brushes in a Critical Binary Mixture, Physica B, in press.

S.K. Satija, P.D. Gallagher, A. Karim and L.J. Fetters, Neutron Reflection from Polystyrene Brushes in a Critical Binary Mixture, Proceedings of International Conference on Neutron Scattering (ICNS) in Physica B, Toronto, Canada, August 1997.

Presentations

A. Karim, B.D. Ermi and J.F. Douglas, Dimensional Cross-over in Phase Separating Thin Polymer Blend Films, Foundation for Research and Technology, Heraklion, Greece, December 1996.

B.D. Ermi, A. Karim, J.F. Douglas and L. Sung, Atomic Force Microscopy Investigations of Phase Separation in Ultrathin Polymer Blend Films, American Chemical Society, Las Vegas, NV, September 1997.

B.D. Ermi, A. Karim, J.F. Douglas and L. Sung, AFM studies of Nucleation and Growth in Off-critical Polymer Blend Films, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

R. Jones, S. Kumar, R. Briber, A. Karim, T.M. Slawecki and T.P. Russell, Phase Separation in Thin Polymer Blend Films, American Physical Society March Meeting, Kansas City, MO, March, 1997.

J.A. Dagata, A. Karim, J.F. Douglas, J.G. Gillen, J. Fu, T. Inoue, H. Yokoyama and J. Itoh, Visualizing Phase Separation in Polymer Systems by Scanning Maxwell-stress Microscopy, STM'97: Ninth Conference on Scanning Tunneling Microscopy/ Spectroscopy and Related Techniques, Hamburg, Germany, July 1997.

A. Karim, B.D. Ermi and J.F. Douglas, Instabilities in Thin Polymer Blend Films, Institute de Chemie des Surfaces et Interfaces, Mulhouse, France, December 1996.

A. Karim, B.D. Ermi and J.F. Douglas, Kinetics of Phase Separation in Thin Polymer Blend Films, Laboratorie de Physico-Chemi, ESPCI, Paris, France, December 1996.

A. Karim, B.D. Ermi and J.F. Douglas, Phase Separation of Ultrathin Polymer Ble.

A. Karim, J.F. Douglas, J.A. Rogers, R.A. Jackman, E.J. Amis and G.M. Whitesides, Phase Separation of Ultrathin Polymer Blend Films on Chemically Patterned SAM Substrates, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

A. Karim, J.F. Douglas and J. Rogers, Control of Film Phase Separation Through Surface Patterning, American Physical Society March Meeting, Kansas City, MO, March, 1997.

A. Karim, B.D. Ermi and J.F. Douglas, Phase Separation in Thin Polymer Blend Films, Max Planck Institute fur Polymerforschung, Mainz, Germany, December 1996.

S.K. Satija, P.D. Gallagher, A. Karim and L.J. Fetters, End-Grafted polystyrene Brushes in a Critical Binary Mixture, American Chemical Society, Las Vegas, NV, September 1997.

A. Karim, C. Laub, S.K. Satija and G.P. Felcher, Relaxation of Polymer Interfaces Below the Glass Transition Temperature, American Physical Society March Meeting, Kansas City, MO, March, 1997.

P.D. Gallagher, S.K. Satija, A. Karim and L.J. Fetters, End-grafted Polystyrene Brushes in a Critical Binary Solvent Mixture, American Physical Society March Meeting, Kansas City, MO, March, 1997.

S.K. Satija, P.D. Gallagher, A. Karim and L.J. Fetters, Neutron Reflection from Polystyrene Brushes in a Critical Binary Mixture, International Conference on Neutron Scattering, Toronto, Canada, August 1997.

Phase Behavior of Polyolefin Blends

K. Migler, A. Nakatani, C. Jackson, A. Karim and E. Amis

Objective

The objective is to characterize phase behavior of polyolefin blends and the effects of shear, pressure and copolymer additives.

Technical Description

Utilize the NIST neutron scattering shear cell and the NIST pressure cell to measure the effects of external fields on polyolefin blend interactions and miscibility.

Examine the miscibility of metallocene copolymers as a function of copolymer architecture and content.

Measure pressure induced shifts of the spinodal curve in critical polymer blends via optical cloud point technique.

Explore the origins of the composition dependence of the interaction parameter of polyolefin blends by probing the response of these systems to pressure.

External Collaborations

- Exxon Research and Engineering- CRADA developed to measure the pressure and shear rate dependence of the phase behavior of metallocene catalyzed polyolefin blends by SANS and optical techniques.

- Polytechnic University - Special synthesis of model polyolefins and study of the effects of external fields.

Accomplishments

In collaboration with Exxon, large pressure induced demixing in metallocene polyolefin blends was demonstrated through optical cloud point measurements. The observed linear dependence of the demixing temperature on pressure is 0.24 /C/MPa. High pressures are typical in most polymer processing, including polyolefins, and the strong dependence on pressure will greatly shift phase boundaries.

Measured the interaction parameter as a function of pressure and temperature for a series of blends consisting of a model deuterated copolymer and various commercial EXACT^TM copolymers, differing by copolymer content and type.

Determined scaling of interaction parameter for several UCST polyolefin blends as a function of density.

Examined the shear behavior of two polyolefin blend types (UCST and LCST) by in-situ shear SANS. Observed behavior similar to shear induced suppression of concentration fluctuations found in prior studies on model blends systems.

Developed a Asmart optical cloudpoint@ software algorithm for pressure cell to increase data acquisition by an order of magnitude.

Outputs

Publications

K.B. Migler and C.C. Han, Pressure Effects on a Diblock Copolymer: Optical Birefringence and Neutron Scattering, Macromolecules, in press.

Presentations

K.B. Migler, The Effect of Pressure on Polyolefin Miscibility, American Physical Society March Meeting, Kansas City, MO, March 1997.

K.B. Migler, The Effect of Pressure on Polymer Diblocks and Blends, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

M. Rabeony and K.B. Migler, Effect of Pressure and Shear on the Miscibility of the Polyolefin Blends, Exxon Chemicals Research Meeting, Galveston, TX, November 1997.

Polymer-Filler Interactions

A. I. Nakatani, A. Karim, B. Lee, J. F. Douglas, S. Glotzer, E. K. Hobbie¹ and E. J. Amis
¹University of Pennsylvania, Philadelphia, Pennsylvania

Objective

The objective is to initiate project to characterize interactions between polymers and fillers in dispersions, in blends and under the effect of shear.

Technical Description

Develop plan for characterizing interactions between polymers and fillers and initiate feasibility studies for conducting planned research.

Determine whether particle inclusions can stimulate the development of concentration waves similar to those found for planar interfaces and, if the phenomenon exists, determine the influence of particle size on this behavior.

Combine numerical and analytical techniques based on Cahn-Hilliard theory to examine the influence of spherical inclusions on mixture phase separation.

Characterize the polymer molecular dimensions, domain sizes and interaction parameters of poly(dimethyl siloxane) (PDMS) blended with silica fillers.

Develop measurement methods appropriate for characterization of instabilities, demixing, nucleation and cluster growth in model hard sphere colloids.

Characterize the role of preferential polymer interactions and the size of the inclusions relative to the correlation length of concentration fluctuations in the two-phase region.

Contrast numerical results with experimental studies of phase separation with inclusions in thin films.

External Collaborators

- Dow Corning Corporation - CRADA developed to examine poly(dimethyl siloxane) (PDMS) blended with filler materials by SANS.

- Building and Fire Research Laboratory, NIST - Provided test samples of silica gel-filled polypropylenes for SANS feasibility studies.

- Goodyear Tire and Rubber Company - Provided test samples of carbon black and fumed silica filled polybutadienes and styrene-butadiene rubbers for SANS feasibility studies.

Accomplishments

Developed and initiated research plans to characterize interactions between polymers and fillers in the following areas: Viscosity and modulus of filled polymer systems; Kinetics and morphology of phase separation and ordering in filled systems; Hydrodynamic behavior and diffusion in filled polymer samples; Interfacial interactions between polymers and filler surfaces.

Contacts made with potential collaborators: Cabot; Goodyear; Dow Corning; Dow Chemical; Building and Fire Research Laboratory (BFRL) at NIST.

SANS experiments on polypropylene filled with silica gel particles performed to assess the feasibility of characterizing filled polymers by SANS. Differences in scattering due to pore volume and surface treatment were easily noted. Differences in scattering due to mechanical preparation and primary particle size were not apparent.

SANS feasibility experiments were performed on carbon black filled and fumed silica filled polybutadiene and styrene-butadiene random copolymer (SBR) (provided by Goodyear). Data analysis in progress.

Conducted simulations of blend phase ordering in the presence of a spherical impurity in two and three spatial dimensions. Demonstrated, within our model, the existence of resulting spherical spinodal waves and quantified the extent of the pattern as a function of quench depth and molecular mass.

SANS measurements on solutions of the individual PDMS and filler components were performed in a collaboration by a Dow Corning scientist.

Obtained radius of gyration of protonated PDMS samples in deuterated toluene which compare well with GPC preliminary to studies on polymer-filler systems. Deuterated polymer synthesis completed by Dow Corning.

Sample cell and experimental method using real time video microscopy was developed for quantitative measurements of kinetics of aggregation of hard spheres.

Demonstrated cluster-size distribution function dynamic scaling in agreement with simulations of two-dimensional evaporation/condensation phenomena.

Outputs

Publications

E.K. Hobbie, Kinetics of Size Segregation in Quasi-Two-Dimensional Nearly-Hard- Sphere Mixtures, Physical Review E, 55, 6281 (1997).

E.K. Hobbie and M.J. Holter, Depletion Force Kinetics in Confined Colloidal Mixtures, J. Chem. Phys., submitted.

Presentations

E.K. Hobbie, Depletion Force Kinetics in Confined Binary Mixtures of Large Colloids, Department of Physics, Rochester Institute of Technology, November 1996.

E.K. Hobbie, Kinetics of Size Segregation in Quasi-Two-Dimensional Nearly-Hard- Sphere Mixtures, American Physical Society March Meeting, Kansas City, March 1997.

E.K. Hobbie, Kinetics of Size Segregation in Quasi-Two-Dimensional Nearly-Hard- Sphere

Mixtures, Department of Physics, Clark University, October 1996.

Characterization and Applications of Dendrimer-Polymer Blends

B. Bauer, E. Amis, A. Topp¹, T. Prosa, D. Valachovic², C. Jackson, D. Liu, A. Karim and J. Douglas
¹University of Koln, Koln, Germany
²University of Southern California, Los Angeles, California

Objective
The objective is to characterize the size, shape and density distribution of dendrimers and the pair interactions between dendrimer pairs and between polymers and dendritic polymers.

Technical Description

Characterize the average radius of gyration and segment density distribution of various dendrimers, dendrigrafts and hyperbranched polymers.

Develop a method of locating the end groups and molecules associated with the end groups of dendrimers.

Develop methods of quantifying the interpenetration of dendritically branched polymers in solution and in blends.

Characterize by TEM dendrimers in solution and on grids as to size, size distribution and interpenetration.

Produce molecularly dispersed dendritic molecules in a polymeric matrix by use of blending and interpenetrating polymer networks.

Prepare monolayer films of dendrimers and measure film thickness by reflectivity.

Measure interfacial thickness between linear polymers and dendrigrafts of differing graft density.

External Collaborations

- Michigan Molecular Institute - CRADA developed for supply of materials, custom synthesis and joint research.

- DSM - collaboration has been established for supply of materials and a guest researcher has been sent to work at NIST on joint research.

- Army Research Office - grant (35109-CH) for work on dendrimer blends; collaboration with Army scientists.

- Mario Gautier, U. Waterloo - collaboration has been established for supply of materials for joint research.

Accomplishments

Dendrimer molecules of divergent types have been characterized with a combination of small angle neutron scattering, small angle x-ray scattering, and transmission electron microscopy. Four critical observations arise from the solution characterization which contrast dendrimers with other classes of polymers: Dendrimers are spherical in shape and have a narrow size distribution even at relatively low molecular mass; the segment density distribution profile is nearly uniform within the dendrimer; the terminal units of the dendrimer are located within a relatively narrow shell toward the periphery of the molecule; and with increasing concentration the dendrimers appear to collapse and pack in a random close packing arrangement with little interpenetration. These characteristics suggest possible applications as size and molecular mass calibration standards for SANS, SAXS, TEM, AFM, MALDI, SEC, and filtration.

Sample preparation techniques have been developed to measure the size and interpenetration of dendrimers in solution and on a surface by TEM.

Molecularly dispersed dendrimers in a polymeric matrix have been prepared by use of blending and IPN techniques.

Monolayers of dendrimers have been placed on a solid substrate and the thickness has been measured as a function of generation showing dimensions in agreement with measurements made by scattering and microscopy.

The interfacial thickness of linear polystyrene and dendritic polyethyloxazoline has been measured and has been found to vary only slightly with generation.

Outputs

Publications

T.J. Prosa, B.J. Bauer, E.J. Amis, D.A. Tomalia and R. Scherrenberg, A SAXS Study of the Internal Structure of Dendritic Polymer Systems, J. Polym. Sci., Polym. Phys. Ed., 35, (1997), in press.

A. Topp, B.J. Bauer and E.J. Amis, Small Angle Neutron Scattering from Dilute and Concentrated DAB(PA)_x Dendrimer Solutions, American Chemical Society PMSE Proceedings, 77, 82 (1997).

B.J. Bauer, A. Topp, T.J. Prosa, E.J. Amis, R. Yin, Q. Qin and D.A. Tomalia, SANS ans SAXS Investigations of the Internal Structure of Dendritic Molecules, American Chemical Society PMSE Proceedings, 77, 87 (1997).

A. Karim, D.W. Liu, B.J. Bauer, J.F. Douglas, E.J. Amis and D.A. Tomalia, Influence of Generation Number on the Formation of Dendrimer Monolayers, American Chemical Society PMSE Proceedings, 77, 181 (1997).

E.J. Amis, A. Topp, B.J. Bauer and D.A. Tomalia, SANS Study of Labeled PAMAM Dendrimer, American Chemical Society PMSE Proceedings, 77, 183 (1997).

C.L. Jackson, H.D. Chanzy, F.P. Booy, D.A. Tomalia and E.J. Amis, Characterization of Dendrimer Molecules by Staining and Cryoelectron Microscopy Techniques, American Chemical Society PMSE Proceedings, 77, 222 (1997).

D.E. Valachovic, B.J. Bauer, E.J. Amis and D.A. Tomalia, Dendrimer End Group Localization Determined by Counterion Mirroring, American Chemical Society PMSE Proceedings, 77, 230 (1997).

J.F. Douglas, R. Lipman, A. Karim and S. Granick, Models of the Influence of Excluded Volume on the Formation of Polymer Layers, American Chemical Society PMSE Proceedings, 77, 644 (1997).

Presentations

E.J. Amis, Probing Dendrimers by Light, Neutron and X-Ray Scattering, NIH Biophysics Research Colloquium, Bethesda, MD, July 1997.

E.J. Amis, Probing Dendrimers by Light, Neutron and X-Ray Scattering, University of Illinois, Department of Materials Science and Engineering, Urbana, IL, September 1997.

T.J. Prosa, A SAXS Study of the Internal Structure of Dendritic Polymer Systems, American PhyAmis, Structural Characterization of Dendrimers by Light, Neutron and X-Ray Scattering, American Physical Society March Meeting, Kansas City, MO, March 1997.

B.J. Bauer, Dendrimers and Dendrimer/Polymer Blends, Center for Interfacial Engineering, Spring Workshops, Minneapolis, MN, May 1997.

B.J. Bauer, Dendrimer Solutions and Blends, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

E.J. Amis, Light, Neutron and X-Ray Scattering of Dendrimers and Dendrimer/Polymer Blends, American Chemical Society Central Region, 100 Years of Dow Chemical Co., Midland, MI, May 1997.

E.J. Amis, Scattering Methods and Dendrimer Materials, American Crystallographic Association, Session on Small Angle Scattering, St. Louis, MO, July 1997.

B.J. Bauer and A. Topp, SANS Study of Labeled PAMAM Dendrimer, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes,@ NIST, Gaithersburg, MD, June 1997.

A. Topp, Small Angle Neutron Scattering from Dilute and Concentrated DAB(PA)_x Dendrimer Solutions, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes,@ NIST, Gaithersburg, MD, June 1997.

T.J. Prosa, A SAXS Study of the Internal Structure of Dendritic Polymer Systems, NIST- ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

A. Topp, Small Angle Neutron Scattering from Dilute and Concentrated DAB(PA)x Dendrimer Solutions, American Chemical Society National Meeting, Las Vegas, September 1997.

B.J. Bauer, SANS and SAXS Investigations of the Internal Structure of Dendritic Molecules, American Chemical Society National Meeting, Las Vegas, September 1997.

A. Karim, Influence of Generation Number on the Formation of Dendrimer Monolayers, American Chemical Society National Meeting, Las Vegas, September 1997.

A. Topp, SANS Study of Labeled PAMAM Dendrimer, American Chemical Society National Meeting, Las Vegas, September 1997.

C.L. Jackson, Characterization of Dendrimer Molecules by Staining and Cryoelectron Microscopy TechniqueDendrimer End Group Localization Determined by Counterion Mirroring, American Chemical Society National Meeting, Las Vegas, September 1997.

Polymer Solutions

E. Amis, R. Ivkov, Y. Zhang¹, B. Ermi², F. Ikkai³, D. Valachovic², B. Bauer and D.-W. Liu
¹The Chinese University of Hong Kong, China
²University of Southern California, Los Angeles, California
³Kyoto Institute of Technology, Kyoto, Japan

Objective

The objective is to characterize molecular interactions and phase behavior of polymers, polymer gels and polyelectrolytes in water and other solvents.

Technical Description

Static light scattering, SLS, and small angle neutron scattering are used to characterize interactions in polyelectrolyte solutions under control of charge density, backbone solvation and counterion concentration.

Dynamic light scattering is combined with SLS and SANS to provide molecular interpretation of coupling of dynamics to structure in polyelectrolyte solutions.

Developed methods using scattering in combination with rheology for characterization of associative polymers and transient gels.

Characterize thermoreversible polyolefin physical gels of ethylene/propylene copolymers in organic solvents and in motor oil.

Investigate the influence of cross-link density, temperature and degree of ionization on the structural inhomogeneities in a weakly charged gel of (N- isopropylacrylamide-co-acrylic acid) copolymers by SANS and compare with recent theoretical treatments.

Develop scattering contrast methods to measure the distribution of counterions in the vicinity of polyelectrolyte spheres and chains.

External Collaborations

- Dendritech and Michigan Molecular Institute - supplied dendrimers for use as model polyelectrolyte spheres.

- Ethyl Petroleum Additives - Collaboration has been established for supply of materials, custom synthesis and joint research. Guest research arrangements for Christophe Daniel and Tse-Chi Jao of Ethyl have been established.

- University of Southern California - two Ph.D. students from the chemistry department completed their thesis research at NIST.

- NIH Biophysics Research Group - initiated interactions in areas of polyelectrolytes, dendrimers and dense media scattering.

Accomplishments

Model for multi-chain domains formed by presence of attractive interaction within polyelectrolyte solutions has been proposed to explain observations of fast and slow diffusive modes in dynamic light scattering and low q upturn in SANS.

Scattering experiments from polyelectrolyte solutions using solvents which are good for both neutral and charged polymers have demonstrated that the so-called "polyelectrolyte effect" cannot be explained adequately by current models based on the influence of residual hydrophobic interactions. Electrostatic interactions dominate the experimental observations.

Polyelectrolyte dendrimers were shown to have dilute solution SLS, DLS and SANS features consistent with observations on linear polyelectrolytes. However, dendrimers cannot be modelled with the electrostatic blobs, extended persistence lengths, or intermolecular entanglements which are often invoked in theories of polyelectrolytes. These observations therefore challenge current models.

The technique of counterion mirroring demonstrates that terminal units of dendrimers in aqueous solution are located predominately at the periphery of the molecule.

Matched deuterium labeled ethylene/propylene copolymers have been synthesized at Ethyl Corporation for initial SANS and neutron diffraction experiments on solutions and thermoreversible gels. Single chain scattering has been measured in both solution and gel states and it has been shown that in the gel state crystalline diffraction peaks appear. Characterization the gelation mechanism is essential for applications of these polymers as additives to control the rheology of industrial lubricants.

Established that microstructural inhomogeneities in weak polyelectrolyte gels have an anomalous dependence on cross-linking by a series of experiments as a function of preparation and experimental conditions. Recent theory for inhomogeneity in gels provides reasonable fitting of the scattering data.

Outputs

Publications

F. Ikkai, M. Shibayama, S. Nomura and C.C. Han, Effect of Degree of Cross-linking on Spatial Inhomogeneity in Charged Gels. 2. Small-Angle Neutron Scattering Study, Macromolecules, submitted.

B.D. Ermi and E.J. Amis, Model Solutions for Studies of Salt-Free Polyelectrolytes, Macromolecules, 29, 2701 (1996).

B.D. Ermi and E.J. Amis, Influence of Backbone Solvation on Small Angle Neutron Scattering from Polyelectrolyte Solutions, Macromolecules, in press.

D.E. Valachovic, B.J. Bauer, E.J. Amis and D.A. Tomalia, Dendrimer End Group Localization Determined by Counterion Mirroring, American Chemical Society-PMSE Preprints, 77, 230 (1997).

Presentations

E.J. Amis, Structure and Dynamics in Polyelectrolyte Solutions, Pennsylvania State University, Department of Materials Science, State College, PA, September 1996.

E.J. Amis, Structure and Dynamics in Polyelectrolyte Solutions, Princeton University, Chemical Engineering Department, Princeton, NJ, November 1996.

E.J. Amis, Structure and Dynamics in Polyelectrolyte Solutions, University of Delaware, Chemical Engineering Department, Newark, DE, December 1996.

E.J. Amis, Structure and Dynamics in Polyelectrolyte Solutions, University of Nebraska, Chemistry Department Colloquium, Lincoln, NB, January 1997.

E.J Amis, Probing Polyelectrolyte Solutions by Light and Neutron Scattering, Rohm and Haas Co. Spring House, PA, March 1997.

E.J. Amis, Polyelectrolyte Solutions: Structure and Dynamics from Strong Interactions, International Conference on Strongly Coupled Coulomb Systems, Boston, MA, August 1997.

F. Ikkai, Effect of Degree of Cross-linking on Spatial Inhomogeneity in Polymer Gels, NIST-ERATO Joint Meeting on AMulticomponent Polymers and Polyelectrolytes@, NIST, Gaithersburg, MD, June 1997.

B.D. Ermi, Probing Polyelectrolyte Solutions by Light and Neutron Scattering, American Chemical Society Colloid and Surface Science Meeting, Symposium on Scattering Methods in Colloid Science, Newark, Delaware, July 1997.

D.E. Valachovic, Dendrimer End Group Localization Determined by Counterion Mirroring, American Chemical Society National Meeting, Las Vegas, September, 1997.

Polymer Blends and Processing Center

E. Amis, A. Bur, C. Han, A. Nakatani, B. Bauer and T. Prosa

Objectives

The objectives are to stimulate adoption of measurement advances and to obtain feedback from industry on successes making use of NIST resssing, by facilitating workshops, improved communications and to develop protocols for user access to measurement facilities for polymer blends and processing.

Technical Description

In collaboration with the NIST Center for Neutron Research and the Applied Mathematics Division of the Information Technology Laboratory, protocols for analysis of small angle neutron scattering are being developed and documented with instructions and examples of standard methods of analysis.

Joined the Participating Research Team for the Advanced Polymer X-ray scattering beamline (X27C) at NSLS-Brookhaven National Laboratory. This provides state-of-the-art small and wide angle measurement capabilities, specifically tailored for use in the characterization of polymer structure.

Electronic mechanisms for communication with industrial collaborators are being prepared including a web site with descriptions of program objectives, highlights of recent work and on-line reprint distribution.

Staff continue to build collaborative relationships and disseminate results of NIST research within the scientific and technical community by organizing meetings, symposia and working groups.

Accomplishments

NIST hosted a three day joint scientific workshop with the Hashimoto Phasing Project of the Exploratory Research and Technology Organization (ERATO) of Japan, which was attended by over 65 representatives of U.S. industry, ERATO, and NIST. In addition to further developing the scientific interactions between these two research groups, the workshop provided U.S. industrial researchers a direct view of the ERATO-supported project.

Contributed to a Dow Corning Corporation resin characterization workshop, with focus on identification of measurement methods to characterize resin fillers.

Held several meetings with Dow Chemical, including visits by their nanocomposites team, resulted in two new cooperative efforts; first, a theoretical modeling project on rheology of filled polymers and second, characterization of polymer-clay interactions by SANS.

NIST hosted an organizational meeting for an Industry-NIST-University-Army Research Consortium on filled polymers. If successful this would be the first ARC and could result in merging Army research interests, industrial participation and strong university involvement for this research area.

Quality of image plate detector data from AP-PRT Brookhaven beamline was compared favorably with data acquired using two-dimensional multi-wire proportional detector at NIST.

Industrial visits and visitors this year: Amoco, Aristech, Cabot, Dow Chemical, Dendritech, Dow Corning, DSM Research, DuPont, Exxon, Ethyl, GE, Goodyear, Packard Electric, Rohm and Haas and 3M.

New collaborations on NIST problems have been established with academic researchers at Polytechnic University (polyolefins), Utah (sensors), Connecticut (ionomer blends), Pennsylvania (multiphase materials), Penn. State (blend rheology).

Symposia were organized at national meetings of Materials Research Society, American Chemical Society and American Physical Society.