Synthesis and Self-Seeding Behavior of Oligo(p-phenylene vinylene)-b-Poly(N-(2-hydroxypropyl) methacrylamide)

Self-seeding of living crystallization-driven self-assembly (CDSA) has been considered to be one of the most attractive strategies to fabricate well-defined fiber-like nanostructures with excellent control over their length and composition. To extend the scope of self-seeding of oligo(p-phenylene vinylene)(OPV)-based copolymers, poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA) segment, with proven biocompatibility, synthetic flexibility and well-developed conjugation chemistry, which was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using an azide-containing chain transfer agent, was coupled with alkyne-terminated OPV block by copper-catalyzed alkyne-azide cycloaddition reaction. All of OPV5-b-PHPMA (OPV5-b-PHPMA36, OPV5-b-PHPMA71 and OPV5-b-PHPMA100, the subscripts represent the number of repeat units of each block) with the same crystallizable core-forming OPV segment but different corona-forming PHPMA blocks of various chain lengths can self-assembled in ethanol to form fiber-like micelles with length of several micrometers by direct heating and cooling process. Uniform fiber-like micelles with the length up to ~ 1 m can be easily prepared by temperature-induced self-seeding of OPV5-b-PHPMA71. However, for self-seeding of OPV5-b-PHPMA36, ribbon-like nanostructures with uniform and controllable length were formed, whereas relative short fiber-like micelles with broad length distributions were formed under similar condition for OPV5-b-PHPMA100. These results indicated that the length of PHPMA segment played an important role in determining the self-seeding behaviors of OPV5-b-PHPMA.