I love finishing the year with a short dive into the dedicated chapter on polymers at the end of my textbook. In my case, I get to spend about two class periods on the chapter before the semester ends. That’s certainly not enough to do justice to every topic in the chapter, but it’s enough to have a substantial impact on my class in two meaningful ways. One impact is on how my students see the direct relevance of our course to their daily lives. This kind of relevance is different from the way our course connects to my students’ professional interests. Most of my students are biology or biochemistry majors and are planning on a career in the health professions, and I routinely make connections to their professional interests by teaching the Organic Chemistry of Biomolecules sections located throughout my book (see the links below for examples of how other users of the textbook incorporate those Biomolecules sections into their course). But those connections come with a bit of delayed gratification for students, because true appreciation for those topics likely won’t come until a student takes a later course in Biochemistry, or is in medical school or graduate school. With our short dive into the polymers chapter, however, my students don’t need to feel like there’s a delayed gratification when it comes to relevance; they can immediately have a better understanding of, and appreciation for, everyday materials—especially plastics and clothing. So when our class discussion turns to polystyrene or polyesters, my students’ engagement visibly ratchets up a notch or two, and that gives me a great feeling as an instructor.
The second impact our short dive into polymers has on my class comes from the way that we use it to review a wide variety of reactions we’ve seen throughout the entire year. We begin with vinyl polymers and the radical polymerizations that produces them, because we just learned about radical chain reactions in the previous chapter; radical polymerization is therefore a natural extension. But we quickly move into the idea that polymers can be made by virtually any reaction we have studied, and that idea provides the motivation for revisiting all sorts of reactions and mechanisms:
- Cationic polymerization of vinyl monomers; electrophilic addition to π bonds
- Anionic polymerization of vinyl monomers; nucleophilic addition to π bonds
- Ring-opening polymerization; SN2 reactions
- Condensation polymerization; nucleophilic addition–elimination reactions
- Network polymerization of Bakelite; electrophilic aromatic substitution
What’s particularly valuable about this review of reactions from earlier in the year is the benefit when it comes to students studying for the cumulative ACS final exam over both semesters.
If your pace through the textbook is a bit quicker than mine, you might also have time to cover other topics of the chapter that revisit early topics, such as physical properties and stereochemistry. Or, if you’re so inclined, you can introduce new material, including coordination polymerization with Ziegler-Natta catalysts, or aspects of recycling polymers.
However you teach the polymers chapter, I hope you and your students find it as enjoyable and valuable as I and my students do.
-Joel Karty, Elon University
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