Facile Access to Chain Length Dependent Termination Rate Coefficients via Reversible Addition−Fragmentation Chain Transfer (RAFT) Polymerization: Influence of the RAFT Agent Structure

Abstract

A recently developed methodology for determining chain length dependent termination rate coefficients, 〈kti,i〉, via reversible addition−fragmentation chain transfer (RAFT) polymerizations has been extended and validated for 1-phenylethyl phenyldithioacetate (PEPDA) and 3-benzylsulfanylthiocarbonylsulfanylpropionic acid (BSPA) mediated styrene (bulk) free radical polymerizations at 80 °C. While the use of cumyl phenyldithioacetate (CPDA) enables a highly precise mapping of the chain length dependence of the termination rate coefficient, employment of PEPDA and BSPA leads to considerable information loss for short chain lengths (i < 10). Careful simulations demonstrate that such behavior is caused by a substantial decrease in the initial transfer effectiveness of the RAFT agents when going from CPDA to BSPA, leading to hybrid behavior between conventional and living free radical polymerization. The observed hybrid behavior is quantifiable via (overall) transfer rate coefficients for the individual RAFT agen...