Molecular Orientation And Dynamics In An Anisotropic Polymer Network

For several decades, polymer science has sought to rationalize the mechanical and thermodynamic properties of polymer networks largely within the framework of statistical thermodynamics. Much of this effort has been directed toward the rubbery rather than the glassy state. It is generally assumed that networks possess an av erage composition to which average properties may be assigned; from such a continuum view, a powerful analysis of such properties as modulus, swelling, birefringence and thermoelasticity has emerged. In the years following the rise of polymer characterization (the late 40's and early 50's), many scientists began to study ap parent relations between the properties of linear polymer molecules and the networks obtainable therefrom. This search was also stimu lated by the wide range of applications of polymer networks in com mercial elastomers, thermosets and coatings. Frequently, these data were confidently matched with curves obtained from statisti cally describable models of networks of ghost chains, uniformly distributed in space. More recently, it has become apparent that polymer chains in networks are not as ideal as assumed in the formulation of statis tical models, and there has been a shift in emphasis towards the less than ideal, perturbed and possibly inhomogeneous networks which are more frequently encountered in practice. The continuum approach, however, had to be developed before inhomogeneous systems could be described; the present volume, therefore, contains both views.

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.

Adopting an integrated approach, this book covers experiments, theory, and emerging applications. In the first part surfaces are described that change from flat to either a random corrugated or to a well-structured structure, while the second part deals with those surface structures integrated in the coating surface where the structures change their shape or dimension when addressed by an external trigger. A variety of materials are addressed, including liquid crystal polymers, hydrogels, hard acrylates, and soft silicones. The whole is rounded off by a discussion of various applications, including surface controlled flows in microfluidic systems. Of interest to chemists and engineers, researchers in industry and academia, as well as those working in the paint industry and hydrodynamics.

A gel is a state of matter that consists of a three-dimensional cross-linked polymer network and a large amount of solvent. Because of their structural characteristics, gels play important roles in science and technology. The science of gels has attracted much attention since the discovery of the volume phase transition by Professor Toyoichi Tanala at MIT in 1978. MDPI planned to publish a Special Issue in Gels to celebrate the 40th anniversary of this discovery, which received submissions of 13 original papers and one review from various areas of science. We believe that readers will find this Special Issue informative as to the recent advancements of gel research and the broad background of gel science.

Talks about various computer simulation techniques used for macromolecular materials. This book describes how to use simulation to explain experimental data and gain insight into structure and dynamic properties of polymeric structures. Explanations are given on how to overcome challenges posed by large size and slow relaxation polymer coils.