Crystallization-Driven Self-Assembly toward Uniform Nanofibers Containing a Donor–Acceptor Core with Near-Infrared Absorption/Emission, Photodynamic, and Photothermal Activities: A Small Variation on the Structure of Donor–Acceptor Segment Matters

Abstract

Although living crystallization-driven self-assembly (CDSA) has emerged as a facile approach to generate uniform πconjugated-polymer-based fiber-like micelles, the extension of living CDSA to prepare uniform donor−acceptor (D−A) fiber-like micelles of controlled length with attractive near-infrared (NIR) absorption/emission, photodynamic (PD), and photothermal (PT) properties is virtually unexplored. Herein, three block copolymers composed of the same corona-forming P2VP 44 (P2VP = poly(2vinylpyridine), the subscript is the degree of polymerization) but different D−A π-conjugated core-forming co-oligomers of OPE 4 -DPP-OPE 4 (OPE 4 = oligo(p-phenylene ethynylene), DPP = diketopyrrolopyrrole) are designed and synthesized to probe the steric and electronic effect of co-oligomers of OPE 4 -DPP-OPE 4 on their CDSA behaviors and photophysical properties. One cooligomer contains a DPP with two 2-ethylhexyl side chains flanked by two thiophene-OPE 4 segments (b-T-OPE 4 -DPP-OPE 4 ). The variation of the second one is the replacement of 2-ethylhexyl side chains with linear octyls (l-T-OPE 4 -DPP-OPE 4 ). The last one is composed of a DPP with two linear octyl side chains flanked by two phenylene-OPE 4 segments (l-P-OPE 4 -DPP-OPE 4 ). Uniform fiber-like micelles can be generated by a self-seeding approach for b-T-OPE 4 -DPP-OPE 4 -b-P2VP 44 and l-P-OPE 4 -DPP-OPE 4 -b-P2VP 44 , whereas polydisperse fiber-like micelles only can be obtained for l-T-OPE 4 -DPP-OPE 4 -b-P2VP 44 likely due to the multiple packing modes of l-T-OPE 4 -DPP-OPE 4 . Intriguingly, the aging of micelles of l-T-OPE 4 -DPP-OPE 4 -b-P2VP 44 can promote the conversion of the packing mode of l-T-OPE 4 -DPP-OPE 4 units to their most thermodynamically stable packing mode, and thus, selfseeding of aged seed micelles of l-T-OPE 4 -DPP-OPE 4 -b-P2VP 44 gave uniform fiber-like micelles of controlled length. More interestingly, micellar solution of b-T-OPE 4 -DPP-OPE 4 -b-P2VP 44 exhibits NIR absorption/emission, PT, and PD activities upon the light irradiation at 660 nm. Although micellar solution of l-T-OPE 4 -DPP-OPE 4 -b-P2VP 44 also shows NIR absorption/emission and PT activity, its PD activity is much lower relative to that of b-T-OPE 4 -DPP a -OPE 4 -b-P2VP 44 . The micellar solution of l-P-OPE 4 -DPP-OPE 4 -b-P2VP 44 exhibits neither NIR absorption/emission nor PT/PD activities upon the light irradiation at 660 nm. All these results showed that a small variation of structure of OPE 4 -DPP-OPE 4 can lead to distinct CDSA behaviors and absorption/emission/ PD/PT properties.

Highly Efficient Preparation of Length and Width-Controllable Donor–Acceptor Nanoribbons via Polymerization-Induced Crystallization-Driven Self-Assembly of Fully Conjugated Block Copolymers

“…Although 1D D–A nanostructures were initially prepared from small molecules, the lack of length controllability or the need for complicated processing (e.g., vacuum deposition at high temperatures) has limited their practicality. , On the other hand, π-conjugated polymers (CPs) are excellent for their solution processability, such as roll-to-roll process, thus providing maximum process efficiency. , Especially, the crystallization-driven self-assembly (CDSA), pioneered by the Manners group, has enabled the formation of various nanostructures (micelles, nanofibers, nanosheets, etc.) and precisely controlled their sizes from CPs, thereby significantly enhancing their applicability. − Furthermore, our group recently developed a novel strategy of the in situ nanoparticlization of conjugated polymers (INCP) containing various crystalline donor moieties (e.g., polyacetylene, polythiophene, and poly­(phenylenevinylene)), where polymerization and self-assembly into various nanostructures occurred simultaneously, eliminating the need for any postprocessing and highlighting greater potential of CPs. − Despite the elegant demonstration and success on CDSA and INCP strategies, their scope has been primarily limited to insulating polymer shell blocks, such as polystyrene or poly­(ethylene glycol), , or with just a few examples of those containing only donor CPs and shells (Figure a). ,− Therefore, the fabrication of unprecedented 1D nanostructures from fully conjugated D–A block copolymers (BCPs) remains a highly desired goal.…”