Thermal properties and molecular simulation of some polyethers and copolyethers with semi-rigid chains

Thermal stability of some aromatic polyethers and copolyethers, containing oxetanic structures in the main chain has been studied. The polymers were s ynthesized using a phase transfer catalysis technique, starting from 3,3-bi s(chloromethyl) oxetane and various bisphenols: 4,4'-dihydroxyazobenzene, 4 ,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenylether and bisphenol A. The cha in geometry tin the case of homopolymers), flexibility and polarity were co rrelated with thermal stability, molecular modeling being used as an additi onal method. All polymers showed good thermal stability, the weight loss st arting above 300 degreesC. The lowest stability was shown by the polymers c ontaining azobenzene units. The most stable product was a copolymer based o n diphenyl and diphenylether units. In the case of homopolymers, the chain geometry influences thermal stability, a linear conformation giving better results compared to a helical one. Increasing of chain flexibility can be c ompensated, from the thermostability point of view, by increased chain pola rity, but only up to a certain value. The heating rate does not influence t he degradation mechanism, as confirmed by a compensation effect investigati on. (C) 2000 Elsevier Science Ltd. All rights reserved.