Self-assembly of PS-b-P4VP block copolymers of varying architectures in aerosol nanospheres

Abstract

Poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) nanospheres are prepared in an aerosol phase where the self-assembly is induced by initial solvent evaporation and subsequent thermal annealing. The block copolymers self-assemble into different structures within solid aerosol nanospheres depending on the relative lengths of the polymer blocks, annealing temperature in the aerosol phase, and solvent composition. The obtained structures are worm-like P4VP domains in a PS matrix with low relative P4VP block lengths whereas alternating lamellae of P4VP and PS in a stacked or onion-like order are found with equal block lengths. With specified solvents and annealing below a glass transition temperature (T_g) this results in phase dimensions smaller than in the corresponding bulk copolymer. At the temperature significantly higher than the T_g the chain segments reach thermal equilibrium, which results in equilibrium structures as in the bulk. The results here show that the instantaneous assembly of polymers blocks in nanospheres can be manipulated in the gas phase to obtain various nanoscale structures which are advantageous, for instance, in designing novel nanosphere-based carrier systems for controlled drug delivery.