Self-Seeding of Block Copolymers with a π-Conjugated Oligo(p-phenylenevinylene) Segment: A Versatile Route toward Monodisperse Fiber-like Nanostructures

Three well-defined crystalline–coil diblock copolymers of oligo(p-phenylenevinylene)-b-poly(N-isopropylacrylamide) (OPV5-b-PNIPAM18, OPV5-b-PNIPAM49, and OPV5-b-PNIPAM75; the subscripts represent the number of repeat units of each block) with the same crystallizable core-forming OPV segment but different corona-forming PNIPAM blocks of various chain lengths were synthesized. Their solution self-assembly behavior was examined in methanol, ethanol, and isopropanol. Both the solvent and the length of the PNIPAM block were found to affect the self-assembly of the block copolymers. In methanol, OPV5-b-PNIPAM18 formed a mixture of fiber-like micelles of uniform width and two-dimensional platelet-like structures with fiber-like micelles protruding from the ends. In ethanol and in isopropanol, this polymer only formed long fiber-like micelles of uniform width. OPV5-b-PNIPAM49 formed long fiber-like micelles (several micrometers) of uniform width in all three solvents, but under the same self-assembly conditions, ...