Temperature- and Solvent-Mediated Confined Assembly of Semicrystalline Chiral Block Copolymers in Evaporative Emulsion Droplets

Self-assembly of chiral block copolymers (BCPs*) not only emerged as a facile strategy to prepare chiral structures but also afforded a key clue to decode and even emulate the vast yet mysterious existence of chirality in nature. Although temperature and solvent properties played a pivotal role in the self-assembly of BCPs* in bulk/films and selective solutions, their impact on BCP* confined assembly is still elusive to date. Herein, we systematically examined the impact of temperature and solvent properties on the 3D confined assembly of polystyrene-block-poly (D-lactide) (PS-b-PDLA) BCPs* in evaporative emulsion droplets. In good solvents for both PS and PDLA, PS-b-PDLA BCPs* featured a kinetically dependent assembly behavior, while enhancing assembly temperature did not show an apparent impact on this trend. It was found that a rapid solvent evaporation was essential to a chiral transfer from PDLA configuration (molecular level) to PDLA microphase separated structure (assembly level) and hence to form chiral particles with an internal helical structure. However, in PS-selective solvents, temperature displayed a considerable impact on particle morphology, with respect to change of the dissolution state of PS-b-PDLA chains and the equilibrium state of assemblies. Moreover, the chirality transfer and the formation of chiral particles were interrupted by the aggregation of PS-b-PDLA chains in selective solvents, but they could be resumed once the aggregates were removed by filtration or employing mixed solvents composed of both good and selective solvents. Accordingly, we highlighted a good dissolution state and rapid assembly kinetics as two prerequisites to the chiral transfer process and the formation of a helical structure under 3D confinement. Our finding enriched the portfolio of assembly scenarios of BCPs* and deepened the understanding on the chiral transfer of BCPs* under 3D confinement.