Chung, Tsai-Ming Wang, Hsiao-Fang Lin, Tao Chiang, Yeo-Wan Chen, Yi-Chun Ko, Bao-Tsan Ho, Rong-Ming Helical Phase Driven by Solvent Evaporation in Self-Assembly of Poly(4-vinylpyridine)-<i>block</i>-poly(l‑lactide) Chiral Block Copolymers A series of chiral block copolymers (BCPs*), poly­(4-vinylpyridine)-<i>block</i>-poly­(l-lactide) (P4VP–PLLA), are synthesized through atom transfer radical polymerization and living ring-opening polymerization. Except for typical microphase-separated phases, such as lamellae (L) and hexagonally packed cylinders (HC), a helical phase (H*) with hexagonally packed PLLA helices in a P4VP matrix can be found in the self-assembly of P4VP–PLLA BCPs*, reflecting the chirality effect on BCP self-assembly. The H* formation is strongly dependent upon the solvent evaporation rate for solution casting at which fast evaporation gives the H* phase and slow evaporation results in the HC phase. To further examine the metastability of the H* phase associated with the dynamics of BCP* chains during self-assembly, P4VP–PLLA BCPs* having different molecular weights at a constant composition are utilized for self-assembly. Under the same evaporation rate for solution casting, the H* phase can be obtained in high-molecular-weight P4VP–PLLA BCP* whereas a stable HC phase is found in low-molecular-weight P4VP–PLLA BCP*, indicating the kinetic origin of H* formation due to the long and highly entangled chains in solution for self-assembly. Consequently, the H* phase can be driven by solvent evaporation through a kinetically trapped process and is regarded as a long-lived metastable phase. PLLA;P 4VP matrix;chiral block copolymers;P 4VP BCPs;HC phase;evaporation rate 2012-12-21
    https://acs.figshare.com/articles/journal_contribution/Helical_Phase_Driven_by_Solvent_Evaporation_in_Self_Assembly_of_Poly_4_vinylpyridine_i_block_i_poly_l_lactide_Chiral_Block_Copolymers/2458276
10.1021/ma302159p.s001