1996 Annual Report

Technical Activities: POLYMER BLENDS AND PROCESSING PROGRAM

Applications of polymer blends 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 therefore more precise definition of blend 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 a copolymer additive 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: measurement technology for on-line characterization of temperature, phase behavior, and shear deformation; shear effects on phase diagrams and phase morphology; activity of additives, compatibilizers, and fillers; and control of interfacial effects in blends and during processing. In each of these areas the program works with industry to develop measurement methods using tools of fluorescence, light scattering, neutron scattering and reflectivity, x-ray scattering, birefringence, microscopy (AFM, TEM, phase contrast), and rheology. CRADA partners and other active industrial collaborators include: Aristech Chemical, Armstrong World Industries, Dendritech, 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 is an outgrowth of the successful completion of two industrial consortia, the Polymer Blends Consortium and the Measurements for Polymer Processing Consortium and is intended to facilitate even greater participation by industrial scientists.

Significant Accomplishments

• Phase separation kinetics of a model polystyrene-polybutadiene blend during shear was measured by light scattering and phase contrast microscopy in collaboration with Goodyear.
  
• Measurements demonstrated homogenization of phase separated polymer blends by mixing under steady shear flow. Analysis and interpretation of the data was based on macroscopic theories of Taylor and Tomotika together with the renormalization and scaling calculations of Onuki and Kawasaki.
• Steady shear behavior of a solvated model polymer blend sample in the two-phase region was measured using fluorescence microscopy. In order to establish a scaling approach to understand shear mixing, phase compositions as a function of shear rate and temperature were obtained.
• The relationship between compatibilizer type and resultant morphology was established by synthesizing compatibilizers of random and graft copolymers having athermal or strong interactions and studying melt blends of immiscible polymers with and without these compatibilizers.
• The shift of phase boundary arising from the addition of diblock and triblock copolymers, and small molecule additives, to polymer blends was measured and are in qualitative agreement with recent theory of such additive induced phase boundary shifts.
• Demonstrated excellent agreement between optical birefringence and small angle neutron scattering measurements of pressure induced phase transition of diblock copolymer.
• Pressure induced shifts in miscibility of polyolefin blends were measured via cloud point technique in collaboration with Exxon.
• Phase separation and kinetics in ultrathin blend films were measured to demonstrate suppression of surface induced phase separation and a transition to the behavior of two dimensional fluid mixtures. Results are in agreement with numerical simulations of phase separation in 2-D.
• Demonstrated the effectiveness of diblock copolymers as compatibilizers in thin films of polymer blends by observation of suppressed surface pattern formation.
• A patent application was filed for a temperature profile sensor based on confocal optics and which fits the standard instrumentation port of processing machines. The sensor was demonstrated by measuring temperature profiles in polyethylene resin during extrusion. The results were consistent with expected effects of shear heating in the barrel of an extrusion machine.
• A new class of fluorescent dyes was identified which can be used as sensor probes at the higher temperatures employed during polymer processing.
• Established solvent conditions that promote micelle formation in ionic graft copolymers. The micelles were characterized using dynamic light scattering, small angle neutron scattering, and TEM.
• Small angle neutron scattering and solvent contrast matching were used to characterize the preferential absorption of small organic molecules into the interior of the micelles as a function of micellar geometry.
• The distribution of condensed counterions associated with the charged terminal units of polyelectrolyte dendrimer molecules in solution was characterized by small angle neutron scattering.
• Demonstrated that the so-called "extraordinary regime" dynamic light scattering and "anomalous" static scattering, usually observed in salt free aqueous polyelectrolyte solutions, is an ionic effect by measurements in non-aqueous polar solvents which are also good solvents for the neutral chain backbone.
• Small angle neutron scattering was combined with static light scattering to cover three decades of q space and scattering intensity to characterize the static scattering from polyelectrolyte solutions. Observation of a peak at high scattering wavevector and upturn at low scattering vector demonstrate that fluctuations occur on multiple length scales in polyelectrolyte solutions. `
• Annual meetings of the Polymer Blends Consortium and Measurements for Polymer Processing Consortium were held. An anthology of research accomplishments from the past decade of polymer blends and processing work at NIST was prepared and distributed to members. The two consortia were merged to establish the new Polymer Blends and Processing Center.

Thermodynamics and Kinetics of Polymer Blends

Measurement Techniques and Analysis Procedures for Multi-Phase Systems Under Shear

Characterization of Polymers and Polymer Blends Under Shear

Temperature Measurements for Polymer Processing

Additives and Compatibilizers in Polymer Blends

Investigation of Interfacial Interactions for Polymers and Blends

Pressure Effects on Polymer Blends and Processing

Self-Assembling Micelles, Transient Polymer Networks, Gels, and Interacting Systems

Investigations of Statics and Dynamics in Polyelectrolytes

Thermodynamics and Kinetics of Polymer Blends

J. Douglas, C. Han, B. Bauer, D. Liu, D. Johnsonbaugh, L. Sung, S. Kim, C. Gettinger, C. Jackson

Objective

The objective is to establish measurement techniques and analysis procedures to characterize phase separation in polymer blends. This project provides support for all other projects which may focus on specific factors, including effects of shear, additives, compatibilizers, pressure, and chemical reactions.

Technical Description

Study influence of finite-size constraints on phase separation of polymer blend thin films by optical microscopy and develop theoretical framework for interpreting these measurements.

Investigate influence of block copolymer additives on the kinetics of blend phase separation in the bulk and in blend films having a range of thicknesses.

Study late-stage phase separation in reactive phase separating blends and develop models of inhibited coalescence and the novel morphologies observed in these systems.

Measure coexistence curve and scattering data (light and neutron) of blends diluted by additives to detemine the extent of critical exponent renormalization.

External Collaborations

University of Chicago - Collaboration to examine the shift of the phase boundary of blends with additives.

Pennsylvania State University - Collaboration to study the influence of finite film thickness on blend phase stability by numerical simulation.

Yamagata University - Collaboration to study the influence of finite film thickness and surface interactions on phase separation models by lattice enumeration methods.

Accomplishments

Investigated influence of block copolymer additives on the kinetics of blend phase separation in the bulk and in blend films having a range of thicknesses.

• Phase separation and kinetics in ultrathin blend films were measured to demonstrate suppression of surface induced phase separation and a transition to the behavior of a two dimensional fluid mixtures. Results are in agreement with numerical simulations of phase separation in 2-D.
  
• Determined kinetics of phase separation in bulk blends with and without symmetric block copolymer additives. Demonstrated slowing down of phase separation kinetics of blend films with additives and inhibition of late stage hydrodynamic coarsening.
  
• Measured shift of phase boundary arising from the addition of diblock and triblock copolymers to polymer blends and compared results to recent theory of such additive induced shifts on the phase boundary.
  
• Measured shift of critical exponents of blends by block copolymer and small molecule additives.
• Investigated role of chemical reaction on late stage blend phase separation. Observed inhibited blend coalescence in these reactive systems.

Outputs

Publications

L. Sung, A. Karim, J.F. Douglas, and C.C. Han, Dimensional Crossover in the

Phase Separation Kinetics of Thin Polymer Blend Films, Physical Review Letters 76,4368(1996).

A. Karim, J.F. Douglas, L. Sung, and B. Ermi, Influence of Dimensionality on the Phase Separation Kinetics of Blend Films, American Physical Society News, in press.

L.L. Sung, and C.C. Han, Light-Scattering Studies on Phase Separation in a Polymer Blend with Addition of Diblock Copolymer, Journal of Polymer Science, Physics Edition, 37, 2405 (1995).

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

J. Dudowicz, K.F. Freed, and J.F. Douglas, Modification of the Phase Stability of Polymer Blends by Diblock Copolymer Additives, Macromolecules, 28, 2276 (1995).

L.L. Sung, A. Karim, J. Douglas, and C.C. Han, Phase Separation in Thin Polymer Bend Films With and Without Block Copolymer Additives, ACS-PSME, 74, 106 (1996).

Presentations

A. Karim, Phase Separation in Thin Reactive Polymer Blend Films, ACS-APS Intersociety Polymer Conference, Baltimore, Maryland, October, 1995.

L.-P. Sung, Dimensional Crossover in the Phase Separation Kinetics of Thin Polymer Blend Films, American Chemical Society, New Orleans, April, 1996.

A. Karim, Inhibited Coalescence in Reactive Blend Films, American Chemical Society, Orlando, August, 1996.

Measurement Techniques and Analysis Procedures for Multi-Phase Systems Under Shear
A. Nakatani, D. Johnsonbaugh, A. Bur, K. Migler, S. Roth, E. Amis, S. Kim, S. Li, C. Han

Objective

The objective is to develop instrumentation, measurement methods, and analysis procedures for multi-phase polymer systems under shear and to transfer these methods to on-line extruder processing applications.

Technical Description

Transfer light scattering and optical microscopy instrumentation and measurement techniques previously developed for a laboratory cone-and-plate shear apparatus to a slit die of a bench top twin screw extruder for on-line morphological characterization.

Contrast controlled shear flow results to measurements made under processing conditions in a slit-die extruder by light scattering, optical microscopy, and fluorescence anisotropy.

External Collaborations

Dow Corning Corporation - CRADA developed to examine polydimethyl siloxane blends blended with highly branched resins by SANS.

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

Raychem Corporation - Polymer Blends Consortium member utilizing SANS to examine liquid crystalline droplets in a polymer matrix.

Planned Outcomes

• Provide instrumentation and techniques for laboratory and on-line characterization of morphological structures for processing design of polymer blends.

Accomplishments

• Steady shear behavior of model polymer blend sample measured by light scattering and phase contrast optical microscopy.
• Phase separation kinetics of a model polymer blend during shear measured by light scattering as a function of shear rate and quench depth.

• Developed fluorescence anisotropy sensor containing polarization optics for real-time processing measurements.
  

Outputs

Publications

S. Kim, J.-W. Yu, and C. C. Han, Shear Light Scattering Photometer with Optical Microscope for the Study of Polymer Blends, Reviews of Scientific Instruments, 67, 1, (1996).

Presentations

S. Kim, Shear Induced Phase Behavior of Polymer Blends Studied by Light Scattering and Microscopic Observation, Intersociety Polymer Conference, Baltimore, Maryland, October 1995.

A. I. Nakatani, Applications of Neutron Radiation to Probe Invisible Structures in Polymer Materials, Dow Corning Corporation and Dow Chemical Company, Midland, Michigan, March 1996.

C. C. Han, Small Angle Neutron Scattering Study of Polymer Blends, CEA, Saclay, France, May 1996.

C. C. Han, Small Angle Neutron Scattering Study of Polymer Blends, KFA, Julich, Germany, June 1996.

Characterization of Polymers and Polymer Blends Under Shear

C. Han, A. Nakatani, K. Migler, B. Bauer, J. Douglas, D. Liu, S. Kim, C. Jackson, L. Sung, E. Amis

Objective

The objective is to characterize polymer blends under shear flow to isolate physical parameters which control morphology and composition of co-existent phases.

Technical Description

• Characterize phase separation kinetics and morphology of polymer blends under the influence of shear by small angle neutron scattering, light scattering, optical and fluorescence microscopy techniques.
  
• Apply measurement techniques to characterize behavior of model polymer systems of commercial interest, including block copolymer melts, liquid crystalline polymers, metallocene catalyzed polyolefin blends, and polymer-oligomer blends.

External Collaborations

Sandia National Laboratories and the University of Cincinnati - Polymer Blends Consortium member utilizing SANS to study polydimethyl siloxane blends.

Goodyear Tire and Rubber Company - Polymer Blends Consortium member utilizing shear light scattering and SANS to characterize the phase behavior of elastomeric blends.

Michigan Technological University - Examine the shear dependence of the order/disorder transition in block copolymers by SANS.

Planned Outcomes

• Provide collaborators and members of Polymer Blends and Processing Center with a sufficiently broad data base to enable testing of models for predicting the shear rate dependent behavior of polymer blends.

Accomplishments

• Spinodal curves of model compatibilized blend system under quiescent conditions measured by SANS as a function of block copolymer concentration.
• Coexistence curves of model compatibilized blend system measured by temperature jump light scattering under quiescent conditions as a function of block copolymer concentration.
• Phase separation kinetics of model compatibilized blend system measured as a function of block copolymer concentration and quench depth.
  
• Quiescent behavior of compatibilized blend system compared to unmodified model blend behavior. Results are the basis for comparison with shear results.
  
• Demonstrated measurements of mixing and homogenization of phase separated polymer blends under steady shear flow, and the analysis and interpretation by macroscopic theories of Taylor and Tomotika together with the renormalization and scaling calculations of Onuki and Kawasaki.
  
• Steady shear behavior of a solvated model polymer blend sample in the two-phase region was measured using fluorescence microscopy. In order to establish a scaling approach to understand shear mixing, phase compositions as a function of shear rate and temperature were obtained.
• Steady shear behavior of model polymer blends with and without additives was measured by SANS as a function of shear rate and temperature. The model systems had either one of the two homopolymers and one of the two blocks of the diblock copolymer labelled or only one block of the copolymer labelled.
• SANS of a diblock copolymer melt was measured as a function of shear rate and temperature. Both steady shear and transient measurements were performed for comparison with previous data on a triblock copolymer melt.
• SANS of a thermotropic liquid crystalline polyether was performed to measure the radius of gyration as a function of shear rate, temperature, and spacer length. Measurements on quiescent samples were also performed for comparison.
• Phase separation kinetics during shear of the model modified polymer blend measured by light scattering as a function of quench depth, shear rate, and additive concentration.

Outputs

Publications

L. Sung, and C. C. Han, Light Scattering Studies on Phase Separation in a Binary Blend with Addition of Diblock Copolymer, Journal of Polymer Science: Polymer Physics Edition, 33, 2405, (1995).

A. I. Nakatani, F. A. Morrison, J. F. Douglas, J. W. Mays, C. L. Jackson, M. Muthukumar, and C. C. Han, The Influence of Shear on the Ordering Temperature of a Triblock Copolymer Melt, Journal of Chemical Physics, 104, 1589, (1996).

A. I. Nakatani, F. A. Morrison, C. L. Jackson, J. F. Douglas, J. W. Mays, M. Muthukumar, and C. C. Han, Shear Induced Changes in the Order-Disorder Transition Temperature and the Morphology of a Triblock Copolymer, Journal of Macromolecular Science - Physics, B35, 489, (1996).

E. K. Hobbie, A. I. Nakatani, H. Yajima, J. F. Douglas, and C. C. Han, Shear Suppression of Critical Fluctuations in a Diluted Polymer Blend, Physical Review E, Rapid Communications, 53, R4322, (1996).

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

R. N. Thudium, and C. C. Han, Microstructure Effect on the Phase Behavior of Blends of Deuterated Polybutadiene and Protonated Polyisoprene, Macromolecules, 29, 2143, (1996).

C. C. Han, Phase Separation of Polymer Blends Under Shear Field, Macromolecular Symposia, 101, 157, (1996).

A. I. Nakatani and C. C. Han, Shear Dependence of the Equilibrium and Kinetic Behavior of Multicomponent Systems, in Structures and Properties of Multi-Phase Polymeric Materials, T. Araki Q. Tran-Cong and M. Shibayama, Eds., Marcel Dekker, New York, NY, in press.

E. K. Hobbie, S. Kim and C. C. Han, String-like Patterns in Critical Polymer Mixtures Under Steady Shear Flow, Physical Review E, in press.

C. C. Lin, S. V. Jonnalagadda, N. P. Balsara, C. C. Han, and R. Krishnamoorti, Neutron Scattering from Multicomponent Flory-Huggins Blends, Macromolecules, in press.

Presentations

L. Sung, The Effect of Block Copolymer as an Interfacial Modifier in Polymer Blends, Intersociety Polymer Conference, Baltimore, Maryland, October 1995.

C. C. Han, Phase Separation and Shear Mixing of Polymer Blends, Intersociety Polymer Conference, Baltimore, Maryland, October 1995.

C. C. Han, Phase Separation and Shear Mixing of Polymer Blends, Physical Chemistry Colloquium, Department of Chemistry, University of Wisconsin, Madison, Wisconsin, November 1995.

C. C. Han, Neutron Scattering from Polymers, Symposium on "Research with Neutrons", The Bavarian-American Friendship Week, Munich, Germany, November 1995.

A. I. Nakatani, Effect of Block Copolymer on the Mixing Behavior of a Polymer Blend, International Chemical Congress of Pacific Basin Societies, Honolulu, Hawaii, December 1995.

C. C. Han, Phase Separation and Shear Mixing of Polymer Blends, International Chemical Congress of Pacific Basin Societies, Honolulu, Hawaii, December 1995.

C. C. Han, Statics, Kinetics, and Pattern Formation of Multiphase Blends, American Physical Society Meeting, St. Louis, Missouri, March 1996.

C. C. Han, Statics, Kinetics, and Pattern Formation of Polymer Blends Under Shear Flow, Karlsruhr Technical University, Department of Physics, Germany, April 1996.

C. C. Han, Statics, Kinetics, and Pattern Formation of Polymer Blends Under Shear Flow, Max Plank Institute for Polymer Research, Mainz, Germany, April 1996.

C. C. Han, Shear Mixing and the Critical Temperature Shift of a Binary Polymer Mixture Under Shear, Koln University, Department of Physics, Germany, April 1996.

C. C. Han, Shear Mixing and Pattern Formation of Polymer Blends Under Shear, University of Freiburg, Department of Physics, Germany, May 1996.

C. C. Han, Fractal Growth and Spinodal Decomposition in a Hydrogen-Bonded Polymer Blends, University of Konstanz, Department of Physics, Germany May 1996.

C. C. Han, Transesterification and Phase Separation of Polymer Blends in Bulk and in Thin Film, University of Marburg, June 1996.

L. Sung, Effect of Copolymer Additives on the Phase Behavior of Polymer Blends, Materials Research Group, NASA Lewis Research Center, Cleveland, Ohio, June 1996.

C. C. Han, Phase Behavior of Polymer Mixtures Under Simple Shear, Gordon Research Conference on Polymer Physics, Newport, Rhode Island, July 1996.

C. C. Han, Shear Mixing and Phase Diagram Shift of Polymer Blends, IUPAC International Symposium on Macromolecular Condensed State, Beijing, China, August 1996.

C. C. Han, Shear Mixing and Phase Diagram Shift of Polymer Blends and Effects of Block Copolymers on the Phase Separation in a Binary Polymer Blend, Chungchun Institute of Applied Chemistry, Academia Sinica, China, August 1996.

C. L. Jackson, Morphology and Phase Separation Kinetics of a Compatibilized Blend , Society of Plastic Engineers ANTEC Meeting, Indianapolis, Indiana, May 1996.

C. L. Jackson, Morphology Evolution and Phase Separation Kinetics in a Polymer Blend with Diblock Copolymer Additive, Gordon Research Conference on Polymer Physics, Poster Session, Newport, Rhode Island, July 1996.

Temperature Measurements for Polymer Processing

A. Bur, K. Migler, D. Johnsonbaugh, S. Roth, E. Amis

Objective

The objective is to develop sensors for measurement of temperature and temperature profiles in polymers under processing conditions. Applications of these sensors will be demonstrated for shear heating effects in polymer blends in simple and complex shear flows, temperature of wire insulation during extrusion, and temperature of films during stretching.

Technical Description

The method uses fluorescent dyes which exhibit changes in their spectrum with temperature.

• Sensors for absolute measurements and ones for temperature profile measurements will be designed to fit standard instrumentation ports on processing machines.
• The temperature profile sensor uses confocal optics to isolate the point of measurement.

External Collaborations

The project involves collaboration with DuPont, Mobil Chemical, and DELPHI Packard Electric.

Accomplishments

• Development of a sensor for measuring temperature profiles which contains confocal optics and which fits the standard instrumentation port of processing machines.
• Measurement of temperature profiles during extrusion of polyethylene through an exit slit die.
• Measurement of shear heating in the barrel of an extrusion machine.
• The discovery of a new class of fluorescent dyes which can be used at high temperatures employed during polymer processing.
• A patent application for this sensor and methodology has been submitted to the Patent Office.

Impact

The technology developed in this project has been used by the 3M Co. in R&D studies of processing technology and is the subject of ongoing collaborations with 3M, DuPont Co., DELPHI Packard Electric and Mobil Chemical Co. The studies with DuPont are being carried out in order to demonstrate measurements of temperature profiles during extrusion and to assess the effects of shear heating. With DELPHI Packard Electric, temperature measurements are being extended to polymer resin during wire insulation extrusion. Mobil Chemical is collaborating with us to apply the methods to temperature measurements of thin polymer films during the stretching process. These companies have all sought the NIST technology because existing temperature measuring methods are inadequate for their processing applications.

Outputs

Publications

A. J. Bur and C. L. Thomas, Volume Viscoelastic Relaxation in a Glass Forming Polymer During Injection Molding, Soc. Plastics Eng. Ann. Tech. Mtg., May, 1996.

Presentations

A. J. Bur and C. L. Thomas, Volume Viscoelastic Relaxation in a Glass Forming Polymer During Injection Molding, Soc. Plastics Eng. Ann. Tech. Mtg., May, 1996.

A. J. Bur, Optical Monitoring of Polymer Processing: Model Developments, Gordon Conf. on Non-Destructive Evaluation, August, 1996.

Additives and Compatibilizers in Polymer Blends

B. Bauer, A. Nakatani, A. Karim, K. Migler, D. Liu, J. Douglas, E. Amis, C. Gettinger, C. Han, C. Jackson

Objectives

The objectives are to develop measurement techniques for characterizing: effects of block copolymer addition and strong interactions on miscibility of polymer blends.

Technical Description

• Develop model polymer systems for measurement of the compatibilization effects of block copolymers and strongly interacting blends.

Characterize the phase diagram and phase separation kinetics of a model polymer blend system without the addition of block copolymers.

• Measure by small angle neutron scattering and light scattering the changes in a model polymer blend system by addition of model block copolymers.
• Measure the strength of hydrogen bonding interactions in model polymers and produce phase diagrams.
• Produce melt mixed immiscible polymer blends with and without various block and random copolymer additives and study the effect of the additives on the dispersions.
• Use our extruder with light scattering/microscopy capability to determine mixing behavior of blends capable of reactive extrusion.
• Determine the effects of film thickness and block copolymer addition on the phase behavior on polymer blends by atomic force microscopy and reflectivity.
• Measure the segment density distribution of dendrimers and associated counterions in solution.
• Prepare dendrimer/linear polymer blends and interpenetrating polymer networks and characterize them by SANS, SAXS, AFM, TEM and reflectivity.

External Collaborations

Michigan Macromolecular Institute - CRADA developed to examine the location of the terminal generation of a dendrimer.

Samples of blends with compatibilizers were produced and distributed to consortium member, 3M Corporation, for transmission electron microscopy.

Accomplishments

Spinodal curves of model compatibilized blend system measured by small angle neutron scattering as a function of block copolymer concentration.

• Determined by temperature jump light scattering coexistence curves of model compatibilized blend system as a function of block copolymer concentration.
• Phase separation kinetics of model compatibilized blend system measured as a function of block copolymer concentration and quench depth.
• Phase diagrams have been constructed for blends that exhibit hydrogen bonding interactions.
• The interaction parameters for blends of polyethylene oxide and poly(methyl methacrylate) and/or polymethacrylic acid have been measured..
• Compatibilizers of random and graft copolymers having athermal or strong interactions have been synthesized. Melt blends of immiscible polymers with and without these compatibilizers have been made, and the relationship between compatibilizer type and resultant morphology has been established.
• Established the effects of film thickness on the phase boundaries and the kinetics of phase separation.
• The internal segment density distribution of dendrimers in solution has been measured. The size and distribution of the counterions in dendrimer solutions has been measured.
• Conditions for forming miscible dendrimer blends have been established.

Outputs

Publications

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

L. P. Sung, and C. C. Han, Light Scattering Studies on the Phase Separation in a Binary Blend with Addition of Diblock Copolymer, Journal of Polymer Science: Polymer Physics Edition, 33, 2405, (1995).

G. Merkle, B. J. Bauer, and C. C. Han, Relaxation After a Temperature Jump Within the One-Phase Region of a Polymer Mixture, J. Chem Phys, 104, 9647, (1996).

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

Presentations

A. I. Nakatani, Effect of Block Copolymer on the Mixing Behavior of a Polymer Blend, International Chemical Congress of Pacific Basin Societies, Honolulu, Hawaii, December 1995.

B. J. Bauer, Compatibilizers Made from Block Copolymers That Have Strong Specific Interactions, ACS National Meeting, March 1996.

L. P. Sung, Phase Separation in Thin Film Polymer Blends With and Without Block Copolymer Additives, ACS National Meeting, March 1996.

B. J. Bauer, Small Angle Neutron and X-ray Scattering Studies of Polyamidoamine Dendrimers MRS National Meeting, April, 1996.

Investigation of Interfacial Interactions for Polymers and Blends

A. Karim, J. Douglas, B. Ermi, D. Liu, E. Amis, C. Han

Objectives

Characterize factors controlling the interface between polymer phases in thin film coatings and phase separated bulk polymer blends. Investigations of thin films on substrates are to be generalized to polymer interactions with fillers in bulk and suspensions in solution.

Technical Description

Characterize equilibrium interfacial profiles in thin films blend coatings as a function of temperature close to the two phase boundary using neutron and x-ray reflection.

Quantify kinetics of phase separation in ultrathin film blends through surface pattern formation using optical microscopy and atomic force microscopy.

Compare results of phase separation in thin blend films with theoretical predictions.

Contrast kinetics of phase separation and morphology development in regular versus reactive blends using atomic force microscopy and neutron reflection.

Use neutron reflection to determine the segregation of block copolymer to interfaces in homopolymer blends.

Characterize the influence of adding diblock copolymer to blend films exhibiting surface pattern formation and examine its role in suppressing the kinetics of phase separation.

Measure the efficacy of diblock compatibilizers as a function of composition and molecular weight.

Investigate modification of surface properties by end-grafted polymers and filler-type materials using x-ray reflectivity and atomic force microscopy.

External Collaborations

3M Corporation - Collaborative project to examine interfacial development in reactive polymer systems using neutron reflection.

Raychem Corporation - Study in-situ blend film phase separation using atomic force microscopy.

Goodyear Tire and Rubber Company - Study phase separation kinetics in ultrathin elastomeric blend films.

Penn State University and University of Maryland - Examine shift of phase boundary in confined thin blend films.

University of Texas - Characterize interface development through transesterification reactions in polymer bilayer films.

University of Connecticut - Synthesis and characterization of properties of grafted polymer layers.

Accomplishments

Determined the evolution of equilibrium concentration profiles in thin film blends as a function of temperature in the vicinity and far from the two phase boundary using neutron reflectivity. Shifts in critical temperatures for confined blend films were estimated using SANS.

Measured the kinetics of phase separation in ultrathin (quasi-two dimensional) blend films and compared with those in thicker and bulk films. Results agree well with existing numerical simulations of phase separation in 2-D.

Observed a strong suppression of phase separation induced surface pattern formation in thin blend films with addition of small amounts of diblock copolymer, demonstrating the effectiveness of diblock copolymers as compatibilizers in thin blend films.

Monitored the slowing down of kinetics of phase separation with diblock addition. The magnitude of this effect cannot be simply explained by a stabilization of the bulk phase boundary with addition of block copolymer.

Measured the development of novel morphology during late stage phase separation in reactive blend films indicating a suppression of coalescence behavior due to the formation of copolymer material through chemical reactions.

Investigated the interfacial evolution in strongly interacting polymer bilayers and observed a strong temperature dependence to the interface healing process.

Successful preparation and characterization of grafted polymer layers under varying solvent conditions and also of spin coated dendrimer thin films.

Outputs

Publications

L. Sung, A. Karim, J. Douglas, and C.C. Han, Dimensional Crossover in the Phase Separation Kinetics of Thin Polymer Blend Films, Phys. Rev. Lett., 76, 4368 (1996).

Y. Feng, R. Weiss, A. Karim, C. Han, J. Ankner, H. Kaiser, and D. Peiffer, Compatibilization of Polymer Blends by Complexation: 2. Kinetics of Interfacial Mixing, Macromolecules, 29, 3919 (1996).

P. Brant, A. Karim, J. Douglas, and F. Bates, Surface Composition of Amorphous and Crystallizable Polyethylene Blends as Measured by Static SIMS, Macromolecules, 29, 5628 (1996).

L. Norton, E. Kramer, F. Bates, M. Gehlsen, R. Jones, A. Karim, G. Felcher, and R. Kleb, Neutron Reflectometry Study of Surface Segregation in an Isotopic Poly(ethylene-propylene) Blend: Deviation from Mean-Field Theory, Macromolecules, 28, 8621 (1995).

A. Karim, V. Tsukruk, J. Douglas, S. Satija, L. Fetters, D. Reneker, and M. Foster, Self-Organization and Structure of Polymer Brush Layers in a Poor Solvent, J. Phys. II France 5, 1441 (1995).

A. Karim, J. Douglas, L. Sung, and B. Ermi, Demixing of Polymer Blends in Ultrathin Films", APS News, in press.

C. Guttman, E. Di Marzio, and J. Douglas, Influence of Polymer Architecture and Polymer-Surface Interaction on the Elution Chromatography of Macromolecules through a Microporous Media, Macromolecules, 29, 5723 (1996).

M. Trache, W. McMullen, and J. Douglas, Segmental Concentration Profiles of End-Tethered Polymers with Excluded-Volume and Surface Interactions, J. Chem. Phys., 105, 4798 (1996).

Y. Feng, R. Weiss, A. Karim, C. Han, J. Ankner, and D. Peiffer, Kinetics of Mixing at Polymer-Polymer Interface Capable of Forming Intermolecular Complexes, ACS New Orleans Polymer Preprints, Spring 1996.

L. Sung, A. Karim, J. Douglas and C. Han, Phase Separation in Thin Polymer Blends With and Without Block Copolymer Additives , ACS-PMSE, 74, 106 (1996).

A. Karim, J. Douglas and C. Han, Frustrated Coalescence in Reactive Blends, ACS-PMSE, Orlando, Fall 1996.

A. Wong, A. Karim and C. Han, Neutron Reflection Studies of Phase Separation and Transesterification in Thin Film Polymer Blends, Physics B, 221, 301 (1996).

A. Karim, J. Douglas, F. Horkay, L. Fetters and S. Satija, Comparative Swelling of Gels and Polymer Brush Layers, Physica B, 221, 331 (1996).

Presentations

A. Karim, Phase Separation in Thin Films of Reactive Polymer Blends, Intersociety Polymer Conference, Baltimore, Maryland, October 1995.

A. Karim, Polymer Brush Profiles in Critical Binary Solvent Mixtures, Intersociety Polymer Conference, Baltimore, Maryland, October 1995.

A. Karim, Frustrated Coalescence in Reactive Polymer Blend Films,International Chemical Congress of Pacific Basin Societies, Honolulu, Hawaii, December 1995.

L. Sung, Dimensional Crossover in Phase Separation Kinetics in Thin Polymer Blend Films, American Chemical Society, Spring Meeting, New Orleans, April 1996.

A. Karim, Kinetics of Mixing at Polymer-Polymer Interface Capable of Forming Intermolecular Complexes, American Chemical Society, Spring Meeting, New Orleans, April 1996.

A. Karim, Self-Organization and Structure of End-grafted Polymer Brush layers, Polymer Physics Gordon Conference, Newport, July 1996.

A. Karim, Inhibited Coalescence in Reactive Blend Films, American Chemical Society, Fall Meeting, Orlando, August 1996.

A. Karim, Atomic Force Microscopy studies of Phase Separation in Polymer Thin Films, American Chemical Society, Fall Meeting, Orlando, August 1996.

L. Sung, Influence of Dimensionality on Phase Behavior of Polymer Blend Films, Reactor Division, NIST, September 1996.

J. Douglas, Surface Pattern Formation Processes in Thin Polymer Layers, Dept. of Chemical Engineering, Princeton, April 1996.

J. Douglas, Surface Pattern Formation Processes in Thin Polymer Layers, Dept. of Physics, Cornell University, Ithaca, April l996.

Pressure Effects on Polymer Blends and Processing

K. Migler, C. Han, E. Amis

Objectives

The objective is to measure the effect of pressure, an important processing variable, on polymer blends, diblock copolymers and supercritical solutions. The focus is on determination of pressure induced changes in miscibility, interaction parameters and radius of gyration.

Technical Description

Conduct cloud point and small angle light scattering studies at high pressure to measure the changes in miscibility of binary polymer blends.

Use small angle neutron scattering to measure pressure induced changes in molecular size, binary interaction parameter and spinodal line of polymer blends.

Use birefringence measurements to determine pressure induced shifts in anisotropic materials such as diblock copolymers and liquid crystal polymers.

External Collaborations

Exxon Research and Engineering Company - CRADA developed to examine the high pressure and shear rate dependence of the phase behavior of metallocene catalyzed polyolefin blends by small angle neutron scattering and optical techniques.

University of Delaware - Examination of polymeric supercritical solutions utilizing small angle neutron scattering.

University of Tennessee - Examine of pressure induced changes in phase diagram of lyotropic liquid crystals.

Accomplishments

Technique for measurement of birefringence at high pressure was developed.

Pressure induced phase transition of diblock copolymer was measured via two complementary techniques: optical birefringence and small angle neutron scattering with the two methods showing excellent agreement.

Measured large pressure induced shifts in miscibility of polyolefin blends via cloud point techniques.

Outputs

Presentations

K.B. Migler, Pressure Induced Order-Disorder Transition in Diblock Copolymers, American Physical Society Meeting, St. Louis, Missouri, March 1996.

Self-Assembling Micelles, Transient Polymer Networks, Gels, and Interacting Systems

C. Gettinger, C. Han, C. Jackson, E. Amis, B. Ermi

Objectives

The objective is to characterize polymers interacting by way of strong specific interactions such as ionic interactions or hydrophobic interactions to form ionic micelles, transient networks, and gels.

Technical Description

Light scattering, neutron scattering, rheological studies, and TEM are used to characterize solubility, size, structure, and interactions of model polymers with specific interacting groups incorporated as ionic grafted copolymers and combs, telechelics, hyper-branched stars, and hydrophobically modified copolymers.

Synthesize and characterize model graft copolymers made up of neutral backbones and ionic grafts.

Small angle neutron scattering, dynamic light scattering, TEM, and computer modeling are used to characterize the solubility, size, shape, and specific interactions of self-assembled micelles as a function of grafting density, concentration, solvent composition, ionic strength, and charge density.

External Collaborations

M. Pitsilklis, J. Mays Department of Chemistry, University of Alabama, Birmingham.

H. Chanzy, Centre de Recherches sur les Macromolécules Végétales, Grenoble, France.

Accomplishments

Selective solvents have been identified for PS/PMAA-Na⁺ and PS/P4VPBz⁺ Br^- graft copolymers and micellization has been observed and characterized in six samples using dynamic light scattering, small angle neutron scattering and TEM.

Structures observed in these systems include multi-molecular spherical micelles with core-shell morphology as well as intra-molecular cylindrical micelles.

With changes in solvent composition, structural changes were observed in micelles of PS/PMAA graft copolymer micelles including reverse micellization. Ionic strength was observed to affect micelle dimensions and chain extension.

Using SANS and solvent contrast matching, the preferential absorption of small organic molecules into the interior of the micelles has been investigated as a function of micellar geometry.

Outputs

Publications

C.L. Gettinger, C.C. Han, M. Pitsikalis, and J. Mays, Micelles Formed by a Model Ionic Graft Copolymer, Polymer Preprints 37(1) 406 1996.

Presentations

E. Amis, Associating Polymers and Transient Gels, Case Western Reserve University, Polymer Science Department, Cleveland, October 1995.

C. L. Jackson, Micelles Formed by a Model Ionic Graft Copolymer, American Physical Society, St. Louis, MO, March 1996.

C. Gettinger, SANS of Micellization of Model Ionic Graft Copolymers in Selective Solvents, American Physical Society, St. Louis, MO, March 1996.

E. Amis , Associations of Model Polymers with Strong Specific Interactions, APS National Meeting, Joint Session of Divisions of Chemical Physics and High Polymer Physics, St. Louis, MO, March 1996.

C. Gettinger, Micelles Formed by a Model Ionic Graft Copolymer, American Chemical Society, New Orleans, LA, March 1996.

E. Amis, Associations of Model Polymers with Strong Specific Interactions, Frontiers in Rubber Science Colloquium, ACS Rubber Division Meeting, Montreal, May 1996.

C. Gettinger, Micelles Formed by a Model Ionic Graft Copolymer, GE Plastics, Selkirk, NY, June 1996.

C. Gettinger, Micellization of Model Ionic Graft Copolymers, 3M Corporate Research, St. Paul, MN, September 1996.

Investigations of Statics and Dynamics in Polyelectrolytes

D. Valachovic, B. Ermi, E. Amis

Objectives

The objective is to provide experimental methods and quantitative data for molecular interpretation of the structure and dynamics of polyelectrolyte solutions.

Technical Description

Measurements with static and dynamic light scattering, small angle neutron and x-ray scattering, and spin echo are used to characterize model systems which provide control of chain conformation, charge density, backbone solvation, and hydrophobic interactions.

External Collaborations

This project is being carried out under in cooperation with the University of Southern California Department of Chemistry.

Accomplishments

First demonstration of so-called "extraordinary regime" of polyelectrolyte behavior in non-aqueous solutions by dynamic light scattering.

Dynamic light scattering from salt free solutions prepared in good solvents for chain backbones show slow mode scattering. This effectively eliminates the argument for microphase separation as the explanation for this persistent effect.

A companion study using small angle neutron scattering verifies the conclusions from the dynamic light scattering and furthermore shows that the peak at finite scattering wavevector is not dependent on backbone solvation in its scaling law with concentration.

Small angle neutron scattering was combined with light scattering to cover over three decades of both q space and scattering intensity and characterize the static scattering from polyelectrolyte solution as a function of concentration. The appearance of a peak at high scattering wavevector and an upturn at low scattering vector were demonstrated conclusively for the first time. These experiments show that current models for polyelectrolyte solutions, which include only a single length scale, are inadequate.

The condensed counterion distribution surrounding polyelectrolyte dendrimer molecules was characterized by small angle neutron scattering.

Outputs

Publications

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

Presentations

E. Amis, Model Polyelectrolytes in Model Solvents, International Symposium on Polyelectrolytes, Potsdam, Germany, September 1995.

E. Amis, Structure and Dynamics of Polyelectrolyte Solutions, Polytechnic University, Chemistry and Chemical Engineering Department Colloquium, NY, November 1995.

E. Amis, Structure and Dynamics in Polyelectrolyte Solutions, Michigan Molecular Institute, Midland, MI, March 1996.

E. Amis, Model Polyelectrolytes in Low-Salt Solutions, International Symposium on Laser Light Scattering, Hong Kong, July 1996.

E. Amis, Structure and Dynamics in Polyelectrolyte Solutions, South China Institute of Chemical Technology, Department of Materials Science, Guangzhou, China, August 1996.

E. Amis, Model Polyelectrolytes in Low-Salt Solutions, IUPAC International Symposium on Macromolecules, Seoul, August 1996.

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