CRYSTALLIZATION AND MELTING OF POLY(OXYETHYLENE) ANALYZED BY TEMPERATURE-MODULATED CALORIMETRY

Temperature-modulated calorimetry, TMC, is used to evaluate the temper ature region of metastability between crystallization and melting. Whi le crystals like indium can be made to melt practically reversibly dur ing a TMC cycle of low amplitude so that sufficient crystal nuclei rem ain unmelted, linear macromolecules cannot, because of their need to u ndergo molecular nucleation. Modulation amplitudes varying from +/-0.2 to +/-3.0 K are used to assess the temperature gap between the slow c rystallization region and the melting of metastable crystals of poly(o xyethylene) (PEG) of molar mass 1500 Da. This low molar mass PEO serve s as a model compound with a metastable gap of melting/crystallization that can be bridged by TMC with a large modulation amplitude. (C) 199 7 John Wiley & Sons, Inc.