CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Two linear polymers, P and Q, have identical molar masses. Polymer P contains one –OH group on every tenth repeat unit, whereas Polymer Q contains only –CH₃ groups. Which polymer is most likely to have the higher glass-transition temperature (Tg), and why?
(a) Polymer Q, because hydrogen bonding in Polymer P increases intermolecular distance, making the chains more flexible
(b) Polymer Q, because its nonpolar –CH3 side groups allow closer chain packing and stronger London dispersion forces
(c) Polymer P, because –OH groups permit hydrogen bonding that restricts chain mobility
(d) Polymer Q, because its smaller side groups enable higher crystallinity, which is incorrectly assumed to increase Tg