Experimental and theoretical insights into cationic polymerization of para-N,N-dimethylaminostyrene

The cationic polymerization electron-rich para-N,N-dimethylaminostyrene (DMAS) for high-molecular-weight polymer is few and highly challenging because of the ease reaction of N,N-dimethylamino group with proton or carbocation. In this contribution, three kinds of initiating systems including Lewis's acid (BF3•OEt2), Brønsted acid (CF3SO3H, TfOH), and the carbocation system (IBVE-HCl/SnCl4, IBVE: isobutyl vinyl ether) were used in DMAS polymerization·BF3•OEt2 showed the highest efficiency for DMAS polymerization to afford high-molecular-weight poly(para-N,N-dimethylaminostyrene) (PDMAS). Copolymerizations of DMAS and 4-methoxystyrene (MOS) were unsuccessful no matter what the monomer feeding mode was, which only produced PDMAS or the blends of two homopolymers. Polymer chain-end analysis and NMR analysis of the intermediate showed that DMAS polymerizations obeyed cationic chain polymerization mechanism. Comprehensive theoretical DFT studies were performed to gain insight into the polymerization mechanism of DMAS. The chain transfer to the dimethylamino group of DMAS monomer was clearly found to be unique and curial to unexpected DMAS polymerization behavior.