Structural factors of rigid-coil polymer pairs influencing their self-assembly in common solvent

This study investigates factors in the structure of rigid and coil polymer pairs that influence their self-assembly in solution. Several pyridine-unit-containing polymers, that is, poly(4-vinyl pyridine) (P4VP), poly(2-vinyl pyridine) (P2VP), copolymers of styrene and 4-vinyl pyridine (SVP), and PS-b-P2VP block copolymer, were used. Their counterparts, the rigid proton-donating polymers, that is, carboxyl-ended polyimide (PI) and poly(amic acid) ester (PAE), were used. All such rigid-coil polymer pairs could self-assemble into hollow aggregates of submicrometer size in their common solvents. The results show a common trend that the hydrodynamic radius of the assembled hollow spheres decreases with the increasing ratio of the rigid proton-donating polymer to the flexible proton-accepting polymer. A new route of micellization of block copolymers with the aid of the rigid polymers is presented. Structure stabilization of hollow spheres composed of PAE/PS-b-P2VP was successfully realized. Furthermore, crosslinking different parts of the hollow spheres led to nanocages totally different in chemistry: crosslinking PAE led to PAE-based nanocages while crosslinking P2VP blocks led to block-copolymer-based nanocages with the rigid PAE chains inside.