Molecular Basis of Polymer Networks

The workshop on the "Molecular Basis of Polymer Networks", held October 5- 7, 1988 in 1iilich, FRG, continued a series of workshops jointly organized by the Institute Laue Langevin (ILL) in Grenoble, and the Institute of Solid State Physics of the KFA, 1iilich. The aim of this workshop was to provide a platform for discussions between theoreticians and experimentalists interested in the physics of polymer networks, in the hope that the two types of discussion would be synergistic. As revealed by the title of this workshop, the main focus of the lectures was on molecular aspects of the problem. The individual parts of these proceedings cover various approaches. Following quite general comments from a physicist examining the situation from "outside", various new theoretical concepts are developed. During the last decade the advent of Small Angle Neutron Scattering (SANS) has allowed the molecular structure of polymer networks to be studied and thus the reliability of the theories to be tested directly at the molecular level. Recent advances in this field are presented. The use of new techniques such as 2H NMR or QELS and the refinements of more classical, mechanical experimental measure ments have provided new information about the relation between the macroscopic behavior and the microscopic structure of polymer networks. Some recent results in this area are discussed for both chemically cross-linked networks and gels built by specific interchain interactions.

Klappentext

The contributors to this volume appraise our knowledge of the molecular physics of polymer networks and pinpoint areas of research where significant advances can be made using new theories and techniques. They describe both theoretical approaches, based on new theoretical concepts and original network models, and recent experimental investigations using SANS, 2H NMR or QELS. These new techniques provide precise information about network behaviour at the molecular level. Reported results of the application of these and more traditional techniques include the microscopic conformation and properties of permanent networks or gels formed by specific interchain interactions, the behaviour of elastomer liquid crystals, and the static and dynamic properties of star-branched polymers.

Inhalt
I Theoretical Concepts.- A Naive Approach to the Physics of Polymer Networks: Remarks, Questions and Prospects.- The Baumgärtner-Muthukumar Effect in Networks.- Statistical Mechanics of d-Dimensional Polymer Networks and Exact Results in Two Dimensions.- Polyelectrolyte Gels: Replica Theory.- Fluctuation-Induced Deformation Dependence of the Flory-Huggins Parameter.- Polymeric Fractal Blends.- II Small Angle Neutron Scattering.- Swelling and Deswelling of Polymer Networks Investigated by Different Types of SANS Experiments: Comments About the Structure.- SANS Probing of Statics and Dynamics of Polymer Networks Under Deformation: Relation Between the Scatterings of Labeled Paths and Labeled Free Chains Dissolved in the Network.- Diffusional Processes in Polymer Networks as Studied by Neutron Spin Echo Spectroscopy.- III Microscopic Conformation and Properties.- Molecular Deformation, Segmental Orientation and Segmental Mobility in Amorphous Polymeric Networks.- Orientational Order Induced in Strained Polymer Networks as Revealed by 2H-NMR.- Effect of Polymer Density on the Orientational Interactions in PDMS Networks: A 2H NMR Study.- Local Orientation and Global Deformation of Network Chains in Strained Elastomeric Networks.- Tests of the Flory-Rehner Hypothesis: Comparison of the Elastic Free Energy Function for Crosslinked Rubber in the Dry and Swollen States.- Swelling of Lightly Cross-Linked Polymer Networks.- Synthesis and Properties of Polystyrene Model Micronetworks.- QELS and SANS Study of Poly(acrylic acid) Gels.- Network Deformation in Flow.- Thermoplastic Elastometers by Hydrogen Bonding.- Salt Effects on Gel-Forming Ionic Polysaccharides.- Investigations of the Complex Shear Modulus and the Optical Rotation in the System Gelatin-Water During theThermoreversible Gelation Process.- IV Model Networks.- The Deformation of Entropic Rigid Rod Networks.- Segment Distribution for Terminally Attached Poly(ethylene oxide) Chains.- Computer Simulation of Model Polymer Networks.- Entropy Elastic Forces of Chain Molecules.- V Liquid Crystal Networks.- Structures and Phase Transition of Elastomer Liquid Crystals.- Liquid Crystalline Polymer Networks.- VI Star-Branched Polymers.- Small-Angle Neutron Scattering from Star-Branched Polymers.- Neutron Spin Echo Investigation on the Dynamics of Star Polymers.- Monte Carlo Simulation of Star Polymers.- On the Viscosity of a System of Star Molecules.- Index of Contributors.