Combination of RAFT and Pd(II)-Initiated Isocyanide Polymerizations: A Versatile Method for Facile Synthesis of Helical Poly(phenyl isocyanide) Block and Star Copolymers

We report a new method for facile synthesis of block and star copolymers composed of helical poly(phenyl isocyanide) and polyacrylate segments via combination of Pd(II)-initiated isocyanide polymerization and reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization. First, an alkyne-Pd(II) complex containing benzyl trithiocarbonate substituent was designed and synthesized. The Pd(II) moiety of the complex can catalyzed the living polymerization of phenyl isocyanides, while the benzyl trithiocarbonate unit can be used as a chain transfer agent for RAFT polymerization. Upon combination of the two living polymerizations, a series of block copolymers containing poly(phenyl isocyanide) and polyacrylate, poly(aryl vinyl) blocks with expected molecular weights (M(n)s) and narrow molecular weight distributions (M-w/M(n)s) can be facilely prepared under controlled manner. Some of these block copolymers exhibited interesting self-assembly and stimuli-responsive properties. Taking advantage of this synthetic approach, core cross-linked star block copolymer carrying polyacrylate-block-polyisocyanide arms can be readily prepared through the copolymerization with a cross-linker, ethylene glycol dimethacrylate. Moreover, miktoarm star copolymers carrying helical polyisocyanides and polyacrylates arms can also be prepared under controlled manner.