上海科技大学知识管理系统

Diblock copolymers (BCPs) with a π-conjugated block and an appropriate block ratio can undergo crystallization-driven self-assembly (CDSA) to form fiber-like micelles of uniform width and length. Almost all examples in the literature involve BCPs with a linear π-conjugated block. We are interested in exploring the influence of the architecture of the π-conjugated block on (living) CDSA of oligo(p-phenylene ethynylene) (OPE) BCPs with a common block length and the same corona-forming block. Herein, we designed and synthesized three OPE7-b-PNIPAM22 BCPs with seven repeats in the OPE block, PNIPAM = poly(N-isopropylacrylamide), with a mean degree of polymerization of 22 which differed only in the architecture of the OPE block. One sample, the reference, had a linear OPE7 block. A second sample had a V-shaped OPE7 with PNIPAM22 attached in the middle (mV-OPE7), and the third sample was V-shaped with PNIPAM22 attached at one end (tV-OPE7). Self-assembly experiments in ethanol/water mixtures led to micelle-like aggregates. The variation of architecture of OPE7 backbone of OPE7-b-PNIPAM22 led into distinct packing modes and different morphologies of the resulting aggregates. Self-seeding experiments with L-OPE7-b-PNIPAM22 gave monodisperse fiber-like micelles of uniform width and tunable length, whereas irregular aggregates or polydisperse ribbon-like micelles were formed by tV-OPE7-b-PNIPAM22 and mV-OPE7-b-PNIPAM22. Important differences were also found in seeded growth experiments designed to form block comicelles with a heterogeneous core junction. L-OPE7-b-PNIPAM22 could efficiently deposit onto the L-OPE9 core of L-OPE9-b-P2VP56 seed micelles (P2VP = poly(2-vinylpyridine) to form triblock comicelles. In contrast, neither mV-OPE7-b-PNIPAM22 nor tV-OPE7-b-PNIPAM22 was able to grow micelles from the ends of the L-OPE9-b-P2VP56 seed micelles. Instead, they formed polydisperse micelles by a self-nucleation and growth process. This work provides instructive information about how the architecture of π-conjugated blocks affects the CDSA of BCPs with a π-conjugated-polymer block, especially under especially self-seeding and heterogeneous seeded growth protocols. © 2022 American Chemical Society.