Polymer science problem areas

III. Some Outstanding Problem Areas in Polymer Science... 

When the Editor wrote his book on Polymer Fracture (Springer 1978) he noted that despite numerous and important publications in the area of crazing many still unsolved problems persisted at that time. So he was delighted that this subject could be brought up to date, thanks to the efforts of some of the most active researchers in this field who, in 1983, contributed to Crazing in Polymers (Advances in Polymer Science, Vol. 52/53, 1983). 

Because polymer science Is by nature Interdisciplinary, the solution of the above problem Involves contributions from many fields, including chemistry, physics, and engineering. The discussion that follows will highlight a number of areas where progress has recently been made in understanding the subject. Considerably more detail will be found in the subsequent chapters of this book. 

The bedrocks of the theoretical and computational methods that allow study of relationships between molecular and mesoscopic scale events and system properties are quantum and statistical mechanics. Thus, this volume comprises chapters that describe the development and application of quantum and statistical mechanical methods to various problems of technological relevance. The application areas include catalysis and reaction engineering, processing of materials for microelectronic applications, polymer science and engineering, fluid phase equilibrium, and combinatorial methods for materials discovery. The theoretical methods that are discussed in the various... 

The subject of polymer blends has been one of the primary areas in polymer science and technology over the past several decades. Judging from publications, patents, major university programs, Ph.D. thesis topics, it continues to maintain significant importance. This will continue, as there are a number of unsolved problems and opportunities. As new areas of interest develop in polymer science, polymer blend technology often becomes an important segment (e.g., electrically conducting polymer blends). 

Another seminal paper by Del Re and his collaborators was in the field of polymers and solids again it concerned the implementation of the Roothaan SCF method, this time to systems with a periodic structure. This important area has developed enormously during the past 30 years, with many applications in new-materials technology and polymer science, but the contribution by Del Re et al. was among the very first in the field. Other relevant papers deal with the problem of surface states and chemisorption, including the definition of electronegativity for a species absorbed on a metallic surface. 

Each of these applications is specific to a particular problem so that uv microscopy should be seen as a technique with some specialised applications rather than being generally useful. Also each new application requires the development of new methods of scimple preparation eind this can be time consuming. In this paper we describe the apparatus and review those areas of polymer science where we have found that this method gives valueible new information. We have recently completed a detailed review of uv microscopy (6) and therefore concentrate on recent advances. 

D-NMR methods have been extensively exploited to tackle problems in polymer science, however, the use of 3D-NMR techniques in polymer science has been rare. Several factors have discouraged the exploitation of these techniques in polymer science, including the scarcity and expense of isotopically labeled monomers and the relatively small amount of funded research compared to that performed in the biological area. Nevertheless, 3D-NMR method can be extremely useful for studying problems in polymer structure, mechanism and properties. In this review, we will summarize some of our work in this area in the hope that it will inspire others to use this methodology. 

The interdisciplinary nature of polymer science and engineering makes it necessary for successful practitioners to be broadly aware of aspects of many fields, from chemistry and physics to materials science to engineering. No one individual can hope to master all these disciplines in depth. It is necessary to possess the ability to recognize what is required to address the problem at hand and to have sufficient acquaintance with the relevant areas to communicate effectively with the appropriate specialists. The contents of... 

A problem area that is not so amenable to mesoscale methods is polymer crystallization. This has proven to be one of the most difficult computational challenges in all of polymer science because the pertinent phenomena operate simultaneously over a wide range of length scales. The pol5uner crystallizes into a particular space group because of atomic detail, and the mechanical properties of the crystallites are determined by, and can only be calculated reliably with, atomic force fields with all atoms represented (126,127). Yet the size of the crystallites or spherulites is so large as to require mesoscopic methods for comprehension. But a crystalline polymer is almost never 100% crystalline. The interphases between crystalline and amorphous domains, with the possibilities for adjacent or nonadjacent reentry and tie-chain distributions, are critical to the properties of semicrystalline polymers. Only recently have models been developed (203) to rigorously address this problem area. 

Monte Carlo simulation is a technique for solving stochastic problems that is widely used in the area of polymer science and engineering. Specifically for studies of polymer microstructures, it has been used to predict the CCD of copolymers and the distribution of stereoregularity [82,83]. One of the advantages of this technique is that one can obtain detailed statistical information of chain structures simply from relatively easy to measure polymer properties such as the CC and the molecular weight. 

We do not discuss however the important field of polymer ionics and polymer electrolytes. This class of materials consists of polar macro-molecular solids in which one or more of a wide range of salts has been dissolved. A classic example that has been studied a great deal is the combination of poly(ethylene oxide) (PEO) containing LiX salt as solute. The reader is referred to a recent monograph edited by Scrosati and to review articles by Vincent, Linford, Owen and to a volume edited by MacCallum and Vincent for further information on this rapidly expanding area of polymer science. The major focus in this chapter (and indeed in this book) is on electroactive polymers used as electrode materials. Polymeric electrolytes, although important in both a technological and fundamental sense, present different problems to those discussed in this volume, and so we restrict discussion to electroactive polymer-based chemically modified electrodes. 

The study of crystalline polymers closely parallels the development of polymer science itself [2]. In placing the subject in proper perspective, it needs to be understood that there are certain areas that are well developed and interpretations that have been accepted for a long time. There are other areas that have been under intensive study and controversy has existed regarding certain aspects of the problems [3]. However, difficulties in interpretation that existed in these cases have gradually been resolved and a set of unifying concepts is emerging. The guiding principles... 

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