Polymers or macromolecules dominate our world. From naturally occurring polymers necessary to sustain life, such as proteins, polynucleotides (DNA, RNA), and polysaccharides (cellulose, starch, chitin, etc.), to the polymers of commerce (polyethylene, polystyrene, polyvinylchloride, nylons, polyesters, rubbers, etc.), macromolecules are the building blocks of choice used to construct the materials found in both the natural and man-made worlds. The dominance of polymeric materials is a consequence of their unique physical properties that result from their long-chain structures and high molecular weights.
These two unique structural features permit individual polymer chains to assume an almost limitless array of sizes and shapes in response to both the environments in which they are placed and the forces to which they are subjected. It is the large sizes and variable shapes which macromolecules can so readily adopt that distinguish them from all other forms of matter and lead to their unique physical properties.
The one-dimensional, long-chain nature of polymers not only results in their ability to respond internally to different environments and stresses, something that small-molecules, atoms, and ions cannot do, but also facilitates an understanding of their properties from a molecular-level point of view.
Backbone bonds in most polymers are easily rotated generally between their preferred staggered conformations, thereby generating a myriad of overall polymer conformations Nconf = Cn , where n = the number of backbone bonds and C =the number of preferred conformations adopted by each backbone bond. Furthermore, the energy associated with any particular backbone bond conformation usually depends only on the conformations of the backbone bond in question and those of its immediate neighbors. For this reason the overall or total energy of a particular polymer chain conformation Econf may be simply estimated through the summation of pairwise-dependent bond conformational energies where corresponds to the local conformational energy when bonds i-1 and i adopt the conformations Øi-1 and Øi.
If the collection of polymer chain conformations Nconf is considered an ensemble of statistical mechanical systems, with each system of the ensemble identified with a particular overall polymer chain conformation, then we may readily evaluate the conformational partition function of the polymer chain and all its attendant thermodynamic properties, because the system energies, Econf , are readily estimable for polymer chains.
Application of matrix multiplication techniques developed for one-dimensional statistical mechanical systems permits the rigorous evaluation of both global and local properties of a single polymer chain, such as its end-to-end distance (size) and local backbone bond conformational populations, respectively, which are appropriately averaged over all of its Nconf conformations. This approach accounts for in a realistic way the detailed microstructural features of polymers which distinguish, for example, polyethylene from polystyrene.
The conformational characteristics of individual, isolated polymer chains and their resulting overall sizes and shapes may in many cases be related to their unique physical properties as manifested in both dilute solution and pure bulk states, where the polymer chains are no longer isolated from each other or from other molecules. When successful, this approach to understanding the behavior of macro-molecules yields a molecular-level knowledge of their structure--property relations, which remains the ``Holy Grail'' in materials science.
Several physical properties unique to polymeric materials are introduced in Chapter 1 and are qualitatively related to their high-molecular-weight, long-chain structures to distinguish them from small-molecule and atomic systems. Step-growth and chain-growth polymerizations are described in Chapters 2 and 3 without introducing more than the necessary elements of organic chemistry. The microstructures of polymers, principally chain-growth vinyl polymers, are introduced and discussed in Chapter 4, including the microstructures of copolymers, branching, and cross-linking. Chapter 5 covers the conformational characteristics of polymers developed with the rotational isomeric states (RIS) model and introduces in an elementary way the matrix multiplication methods necessary for the calculation of polymer chain properties that are appropriately averaged over all of their conformations.
Chapters 6 and 7 describe the solution and bulk properties of polymers with emphasis placed on their connections with the conformational characteristics of individual polymer chains. We close with a chapter (Chapter 8) on biopolymers, where the emphasis is placed on the connections between their microstructures (primary structures), conformations (secondary structures), overall sizes and shapes (tertiary structures), and properties (biological functions). Here is presented the inescapable conclusion that life is not possible without polymers.
In the early portion of each chapter, topics are intoduced and elementary examples and illustrations of the requisite concepts and methods are provided. In the remaining portion of each chapter these topics, concepts, and methods are elaborated upon, and sometimes additional new material is introduced and discussed. Organization of material in this format is designed to facilitate its use in teaching either a one-or two-semester undergraduate course in polymer science. In the one-semester course only the early portions of each chapter need be covered, while in the second semester of the two-semester sequence course the initial material in each chapter may be quickly reviewed with the remaining material serving as the focus of coverage in each chapter.
Simple classroom demonstrations appropriate to the material covered in each chapter are described, and several questions raised by each demonstration are posed to generate student inquiry. Also a set of homework questions and problems are provided at the end of each chapter, and those believed appropriate for second-semester students are denoted with an asterisk.
We take the above approach to presenting the covered material, because we believe that all students should be exposed to the topics covered in each and every chapter, with expanded, more in-depth coverage of the same topics for those students fortunate to have access to a two-semester course in polymer science.
Alan E. Tonelli
Mohan Srinivasarao
