Self-assembly of rod-coil diblock copolymers influence of the rod length

The self-assembly of five narrowly distributed novel rod-coil diblock copolymers, poly(styrene-block-(2,5-bis[4-methoxy-phenyl]oxycarbonyl)styrene) (PS-b-PMPCS), in p-xylene, a selective solvent at room temperature, was studied. The rod-coil copolymers, which have the same PS length but different PMPCS length, were synthesized by 2,2,6,6-tetramethyI-/piperidinyloxy (TEMPO) mediated living free radical polymerization. The influence of the rod length on the self-assembly morphology was studied by transmission electron microscopy (TEM). At a concentration of 2.0 mg/mL, those copolymers with relatively shorter PMPCS length (copolymers 1 and 2) form individual spherical micelles; those with relatively longer PMPCS length (copolymer 3 and 4) form 'pearl chains' coexisting with individual spherical micelles; the ones with longest PMPCS length form 'pearl chains' coexisting with occasionally formed nanofibers. The diameter of all the morphologies was controlled by the rod length. This gives us a way to govern the self-assembly morphology by altering the length of one block in the block copolymer.EI