ANNEALING EFFECTS ON THE THERMAL-PROPERTIES OF LIQUID-CRYSTALLINE POLYURETHANES

This work is a continuation of our earlier investigations of liquid crystalline polyurethanes prepared from 4,4'-bis(2-hydroxyethoxy) biphenyl (BHBP), 2,4-tolylene diisocyanate (TDI), and poly(oxytetramethylene) diols (PTMO). The annealing effects on the thermal properties of the investigation polyurethanes are presented for three samples with the same BHBP content, different flexible spacer length, and different molecular weight of the polyurethanes. The annealed polyurethanes were investigated by means of DSC, and polarizing microscopy. The results of the thermal analysis show that the temperatures of phase transitions depend on the annealing temperature and time. These dependences are different for different molecular weights. (C) 1994 John Wiley & Sons, Inc.