CATIONIC POLYMERIZATION OF 1,2-EPOXY-6-(9-CARBAZOLYL)-4-OXAHEXANE

The polymerization of 1,2,-epoxy-6-(9-carbazolyl)-4-oxahexane (ECOH) by Lewis acids (SbCl5, SnCl4, SnBr4, SnI4) in 1,2-dichloroethane has been studied. The kinetics have been studied by a microcalorimetric method. The most active catalyst of those studied was SbCl5. The activity of SnCl4 is close to that of SbCl5 but SnBr4 and SnI4 are considerably less active. Reaction orders with respect to monomer and catalyst have been established for all the catalytic systems except that containing SnBr4. ECHO polymerization with the Lewis acids can be roughly divided into two stages vis. initial (fast) and long lasting (slow). Spontaneous increase of polymerization rate has been observed in the slow stage. It is the first reported observation of this effect for the cationic polymerization of epoxides. Continuous increase of molecular weight of oligomers has been recorded during the slow state of polymerization. Mechanistic aspects of regeneration of active species are discussed.