WELL-DEFINED COLUMNAR LIQUID-CRYSTALLINE POLYDIETHYLSILOXANE

The kinetics of the anionic ring opening polymerization of hexaethylcy clotrisiloxane (D-3(Et)) with the cryptate Li+/[211] as counterion hav e been studied by means of C-13 NMR spectroscopy. The propagation reac tion was found to be of first order in monomer as well as living end c oncentration. It proceeds by two decades slower than the corresponding reaction with hexamethylcyclotrisiloxane (D-3(Me)) as monomer. The Li +/[211] system could be used to synthesize well defined polydiethylsil oxane (PDES) samples ((M) over bar(w)/(M) over bar(n) <1.2). However, when the polymerization eras aimed at high molecular weights (greater than or equal to 600 000 g/mol), the obtained molecular weights were l ower than expected, and the molecular weight distributions became broa der. All PDES samples were capable of forming a columnar mesophase. Th e temperature range in which this phase exists was found to be strongl y molecular weight dependent. Initiation of the D-3(Et) polymerization with polybutadienyl-lithium and coupling of the living chain ends yie lded a PB-PDES-PB triblock copolymer, which could be crosslinked, resu lting in a mesomorphic network.