Morphological transition and transformation of 2D nanosheets by controlling the balance of π–π stacking interaction and crystalline driving forces

Nanoscale organic two-dimensional (2D) materials of block polymers (BCPs) have attracted interest on account of their wide potential applications in a range of fields. Herein, we design a new poly(p-phenylenevinylene) (PPV) based BCP that contains a triisopropylsilyl side chain and poly (2-vinyl pyridine) (P2VP) corona, which could assemble into a series of 2D square and rectangular micelles in isopropanol. The aspect ratios and the scales of the 2D micelles can be tuned in two ways, including altering the ratios of the P2VP and PPV-TIPS blocks and their concentrations. By precisely controlling the aspect ratios, micro-scale rod-like micelles are also obtained. From in depth studies of the morphology transition from rectangular micelles to rod-like or square micelles, it is found that the BCPs initially organize into fibers and then assemble into final micelles by the combined forces of π-π interactions and the crystalline force from TIPS side chains. Based on the balance of the two interactions, 2D circle-like micelles are also achieved by heterogenous co-assembly of two kinds of polymers with different cores.