Stretching the Cwriculum tor Polymers A strong case can he made for including information about polymers& introductory chemistry courses. Polymers will probably have an impact on the average student's life more than any other chemical substance &sides air and water (and possibly alcohol); thus, nonscience majors, even those who have been enrolled in chemistry against their natural inclinations, should find the topic interesting. Chemistry maiors will have not onlv the above reason but also an added impetus to learn about polymers when they realize the majority of professional chemists are doing research that is related to polymer chemistry. Why then is polymer chemistrv not uervasive in the introductow chemistrv course? One eiplana&n is that polymer chemistry has so lbng been relegated to the specialty upper division and graduate courses that those teaching the introductory courses have seldom had any formal course work on the subject. Faced with an already tight schedule, they are reluctant to try to fit in material that they are not familiar with and for which they know few . oedaeoeic methods. Thus.. thev.omit discussion of polymers, producing another generation of teachers who are uncomfortable with presenting the topic. To help teachers break this cycle, a series of articles in this issue provides an introduction to the topic andsome specific ideas for teaching the basic concepts in a lively manner. One of the harriers to learning about polymers is the unfamiliar nomenclature, which is complicated by the fact that there are several systems in use. C a r r a h e r (page 36) explains each of the most commonly encountered approaches to naming and gives examples of their applications. This article is comolemented hv a dictionarv of terms descrihine the physical aspects of polymer structure, which appeared in the May 1986 issue (page 418); together they make a good introductory primer for the novice. Students should he most interested in the ~olvmersthat they encounter in their daily lives: those that &ecommonly referred to as "ulastics". Deanin (page 45) enumerates the technical advaitages that make plastics so pervasive in our society and then gives details of the production of the most common ones, such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyesters. The more specific application of plastics as thermal insulating materials are
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Journal of Chemical Education
discussed by Wang and Grossman (page 39), who give both general considerations and specific examples of plastic foams currently used for these purposes. Seymour (page 63) takesa wider view in "Chemicals in Everyday Life", in which he describes polymers in the context of many other classes of compounds that have an impact in the food we eat, the clothes we wear, our living environments, and even our recreational pursuits. Three articles that also serve as a resource for information on the applications of polymers in modern society appeared in the May 1986 issue; they covered polymers used in disposable diapers (page 422), membranes and films made from clolvmers (oaee . - 414). and uauer .. as a modified polymer (page426). Polymers have amyriad of uses uartlv because their ~ h v s i cal properties can he manipulated h i varying their-chain lengths and stereo configurations. Demonstrating this relation brrwren pulymer st&rure and physical properries is a gwd pwnt of deplrfure ior bringing polymers into the clnssroom. For example, a common property associated with polymers is their elasticity; Clough (page 42) describes a simple urocess for demonstratine that. counter to what one woGld expect, a stretched elastomer will decrease in length when it is heated. He goes on to show how this phenomenon is linked to the entropy of stretched versus the unstretched chains. Another familiar characteristic of some uolvmers is their ability to rebound a surprising distance when they hit a hard surface. The thermodynamics of this process as i t relates to the internal polymer structure is discussed by Carr a h e r (page 43), who contrasts it with what happens when a metal ball hearing impacts the same surface. For teachers wanting a visible illustration of the polymer principles, Rodriguez, Mathias, Kroschwitz, and Carr a h e r (page 72) show how they employ commonly available materials, such as pop-it beads, in a series of demonstrations of polymer structure and behavior. This article in the series covers wavs to illustrate size of macromolecules. cooolvmers. and methbds of determining molecular mass. ~ i r s h e n b a u k (page 47) presents a list of societies and associations that have information, teaching aids, and other materials available for classroom use. The listine includes complete information about what is available an2 how it can h;obtained. ~~
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