Organic acids as efficient catalysts for group transfer polymerization of N,N-disubstituted acrylamide with silyl ketene acetal: polymerization mechanism and synthesis of diblock copolymers

The group transfer polymerization (GTP) of N , N -diethylacrylamide (DEAA) was studied using various combinations of an organic acid of N -(trimethylsilyl)bis-(trifluoromethanesulfonyl)imide (Me 3 SiNTf 2 ), 1-(2,3,4,5,6-pentafluorophenyl)-1,1-bis(trifluoromethanesulfonyl)methane (C 6 F 5 CHTf 2 ), and tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) and a silyl ketene acetal (SKA) of 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene ( Me SKA), 1-methoxy-1-(triethylsiloxy)-2-methyl-1-propene ( Et SKA), 1-methoxy-1-(triisopropylsiloxy)-2-methyl-1-propene ( iPr SKA), and 1-methoxy-1-(triphenylsiloxy)-2-methyl-1-propene ( Ph SKA), among which the combination of B(C 6 F 5 ) 3 and Et SKA afforded a relatively better control over the molecular weight distribution. The polymerization behavior of DEAA using B(C 6 F 5 ) 3 and Et SKA was then intensively investigated in terms of the polymerization kinetics, chain extension experiments, and MALDI-TOF MS analyses, by which the polymerization was proven to proceed in a living fashion though an induction period of tens of minutes occurred. The B(C 6 F 5 ) 3 -catalyzed GTP was further extended to various N , N -disubstituted acrylamides (DAAs), such as N , N -dimethylacrylamide (DMAA), N , N -di- n -propylacrylamide (D n PAA), N -acryloylpiperidine (API), N -acryloylmorpholine (NAM), N -(2-methoxyethyl)- N -methylacrylamide (MMEAA), N , N -bis(2-methoxyethyl)acrylamide (BMEAA), N , N -diallylacrylamide (DAlAA), and N -methyl- N -propargylacrylamide (MPAA). Finally, the livingness of the polymerization was used to synthesize acrylamide–acrylamide block copolymers and methacrylate–acrylamide hetero-block copolymers.