Fragmentation of polycarbonate macroinitiators in solution and in the bulk state

Abstract

AbstractThe diphenylethane initiator 3,4‐diethyl‐3,4‐(p‐methoxyphenyl)‐hexane (T–OCH3) was synthesized. By cocondensation of bisphenol A or C and the bisphenol derivative (“T”) of T–OCH3 with phosgene, polycarbonate macroinitiators PC(TxA1‐x) and PC(TxC1‐x) with different compositions x were made. The thermal fragmentation of T–OCH3 and the copolycarbonates was investigated with and without a radical scavenger both in solution and in the bulk state. The primary dissociation of T–OCH3 is a monomolecular Arrhenius process with a characteristic temperature of T* (τ = 1h) = 140°C (τ: average life time of the intact molecule). When the radicals are not intercepted, the dissociation is excessively reverted by radical recombination, which raises T* to T* = 163°C. The reaction ends then exclusively in radical disproportionation. The chain fragmentation of the copolycarbonates is of the type of a random decondensation. The counits CT dissociate in solution almost exactly like T–OCH3. In the highly viscous bulk state, the reaction proceeds in matrix cages, which have a stabilizing effect, so that T* is increased to T* = 170°C. These copolycarbonates are model polymers for a novel method to study the hitherto unmeasurably slow chain diffusion processes in polymers near the glass transition temperature.