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

摘要

In this work, the reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc) was successfully performed at room temperature using ~(60)Co γ-irradiation as the initiation source. Under the dose rate of 10Gy/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 ℃, ~(60)Co γ-irradiation-initiated RAFT polymerization is a technique that can better control the molec ular weight, especially at high conversion. The H NMR spectra and matrix-assisted laser desorption/ion ization 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 ~(60)Co 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, ~(60)Co γ-irradiation was used as an initiation source for RAFT polymeriza tion of VAc at room temperature.