60Co γ-irradiation-initiated RAFT polymerization of VAc at room temperature

Abstract

In this work, the reversible addition–fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc) was successfully performed at room temperature using 60Co γ-irradiation as the initiation source. Under the dose rate of 10 Gy/min irradiation, the polymerization proceeded smoothly and converted approximately 90% of the monomer within 7 h. The molecular weight distribution ( M w/ M n) remained narrow ( M w/ M n < 1.35) up to 90% conversion. Compared to AIBN-initiated RAFT polymerization at 60 °C, 60Co γ-irradiation-initiated RAFT polymerization is a technique that can better control the molecular weight, especially at high conversion. The 1H NMR spectra and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry confirmed that most of the chain ends of poly(VAc) (PVAc) from γ-irradiated RAFT polymerization were living and can be reactivated for chain-extension reactions. The microstructures of PVAc from 60Co γ-irradiated RAFT polymerization (almost head-to-tail addition) and AIBN-initiated RAFT polymerization (5% tail-to-tail addition) were different, as revealed by the 13C NMR spectra. For the first time, 60Co γ-irradiation was used as an initiation source for RAFT polymerization of VAc at room temperature.