Influence of Sequence Structure of Donor/Acceptor-Containing Segment on Crystallization-Driven Self-Assembly Behavior...

Crystallization-driven self-assembly (CDSA) has emerged as a facile strategy to generate donor-acceptor (D-A) π-conjugated nanofibers with potential applications from photocatalysis to nanomedicine. However, the reports on CDSA of D-A π-conjugated-polymer-based block copolymers (BCPs) are rather rare. In this context, we report two types of BCPs containing the same corona-forming poly(N-isopropylacrylamide) segment, but different core-forming D-A π-conjugated blocks, one of which (BT-OPE₅-BT) contains an OPE₅ segment flanked by two electron-deficient benzothiadiazole (BT) unit and another one of which (B-alt-BT) contains four phenylene (B) units and three BT units placed in an alternate way. The BT-OPE₅-BT-based seed micelles were not kinetically frozen with obvious micellar dissolution at room temperature, whereas almost no micellar dissolution occurred for B-alt-BT-based seed micelles. However, only polydisperse fiber-like micelles can be formed by self-seeding approach owing to presence of multiple packing modes for B-alt-BT-b-PNIPAM₃₆ over the micellar elongation. The B-alt-BT exhibited much more pronounced intra/intermolecular charge transfer effect than BT-OPE₅-BT, and thus the micelles of B-alt-BT-b-PNIPAM₃₆ exhibited about 50 nm red-shift in UV/vis absorption band than that of BT-OPE₅-BT-b-PNIPAM₃₆ and appealing photocatalytic hydrogen evolution activities. This work highlights the importance of sequence structure of D/A units of D-A segments on both CDSA behavior and photophysical/ chemical properties.