RAFT Polymerization Kinetics of a-Methylbenzyl Methacryalte by Dilatometry

Abstract

This work presents a comparative study of the reversible addn.-fragmentation chain transfer (RAFT) and free radical polymns. of α-methylbenzyl methacrylate (α-MBM) in soln. at 70 °C using 1-phenylehtyldithiobenzoate (1-PEDB) as RAFT agent and AIBN as thermal initiator. Reactions were monitored by dilatometry, which is a robust and economical technique to follow kinetic polymn. Free radical polymns. were carried out at initial monomer concn. [α-MBM]0 of 0.2, 0.5, 0.7 and 1.0 M at fixed [AIBN]0 = 1 × 10-3 M and initial initiator concn. of 2, 5, 8 and 10 × 10-3 M at fixed [α-MBM]0 = 0.5 M. For the RAFT polymns. the [1-PEDB]0 was 4 × 10-3 M using the same reaction conditions as that in the free radical polymns. In RAFT polymns. it was found that conversion profiles were lower than in free radical polymn. Plots of conversion vs. time indicated that the polymns. followed first order kinetics in the range of [α-MBM]0 evaluated. However, only at low [AIBN]0, i.e. 2 and 5 × 10-3 M, kinetics fitted adequately in the reaction time tested. 1H NMR, IR, and UV-Vis spectrophotometric studies confirmed the presence of thiocarbonylthio moieties (-SCS-) in the polymer chains. Mol. wt. data for the set of expts. carried out by free radical polymn. decreased when the monomer or the initiator concn. increased. The mol. wt. distributions (M WDs) corresponding to the polymers obtained in the RAFT polymns. were moderately narrow with polydispersities (D) between 1.12 and 1.59. [on SciFinder(R)]