Effect of block ratios on self-assembly morphologies of poly(ε-caprolactone)-block-poly(tert-butyl acrylate) block copolymer

Abstract

Crystalline-coil block copolymer compositions, determined by block ratios, play a vital role in the construction of different self-assembly morphologies. Here, we synthesized a series of crystalline-coil block copolymers with different block ratios, namely poly (ε-caprolactone)-block-poly (tert-butyl acrylate) (PCL-b-PtBA), to explore the impact of polymer compositions on self-assembly morphologies via crystallization-driven self-assembly (CDSA). It was found that the PCL-b-PtBA can self-assemble into various morphologies including lozenges, quadrilaterals, elongated hexagons, hexagonal platelets, saw blade platelets and spindle micelles. Additionally, transmission electron microscopes (TEM) imaging indicated a gradual morphological transformation from quadrilateral to lozenge platelets, and then to elongated-hexagon platelets with high aspect ratios as the sampling time was prolonged. We hypothesize that variations in polymer composition lead to changes in the self-assembly morphology primarily due to differences in the reduced tethering density of PtBA segments with varying chain lengths, which subsequently impacts the crystallization of PCL. Our work reveals that adjusting block ratios of the PCL-contained block copolymer for self-assembly is a facile way to construct diverse morphologies of polymer materials, and the corresponding materials may have potential applications in fields such as drug delivery, antibacterial treatments and other fields.