P4 (10 points). This question is related to your knowledge of how chemical structure affects a polymers glass transition temperature. For each pair below draw the repeat unit of the polymers, select which polymer you believe has a higher glass transition temperature, and explain your answer.

Pair 1: polyethylene versus poly(vinyl alcohol)

Pair 2: poly(hydroxyethyl methacrylate) versus poly(propyl methacrylate) Pair 3: poly(vinyl chloride) versus poly(vinylidene chloride).

Important note: The two primary mechanisms that affect glass transition temperature are: (1) complexity of side chains; and (2) backbone flexibility. The number and complexity of side groups can increase Tg (think in the context of how difficult it will be to break bonds) - branching of side groups can further increase Tg. Presence of plasticizers can decrease Tg because plasticizers increase the flexibility of polymers. Polarity increases Tg because the more polar groups (e.g. Cl and OH) lead to increased dipole-dipole interactions.