Controlled grafting of cationic poly[(ar-vinylbenzyl)trimethylammonium chloride] on hydrogen-terminated silicon substrate by surface-initiated RAFT polymerization

Controlled grafting of well-defined cationic poly[(ar-vinylbenzyl)trimethylammonium chloride] [poly(VBTAC)] brushes on a hydrogen-terminated silicon substrate (SiH) was performed via surface-initiated RAFT polymerization. The azo-initiator was immobilized on the SiH surface via a three step process involving (i) coupling of the t-butyloxycarbonyl (t-BOC) protected allylamine to the SiH surface under UV irradiation, (ii) conversion of the t-BOC protected allylamine groups into the free amine groups by trifluoroacetic acid, and (iii) the amide reaction of allylamine with the 4,4′-azobis(4-cyanopentanoyl chloride) initiator. The living polymerization produced silicon substrate coated with well-defined cationic poly(VBTAC) with a target molecular weight and a grafting density as high as 0.93 chains/nm2.