Formation of biomimetic hierarchical nanostructure in homopolymers and block copolymer ternary blend particles

In order to mimic hierarchical nanostructures in nature, particles of polymer blends consisting of poly(4-butyltriphenylamine) (PBTPA), poly(methyl methacrylate) (PMMA) and PBTPA-block-PMMA were fabricated by a solvent evaporation method. Effects of the molecular weight and the chemical composition of PBTPA-b-PMMA, molecular weights of homopolymers, and the composition of the blend on the morphology were investigated. The polymer blend particle consisting of PBTPA and PMMA homopolymers exhibited thermodynamically favored core-shell structure, in which more hydrophilic PMMA-shell surrounded PBTPA-core. The addition of 10 wt% of PBTPA-b-PMMA caused the morphological transition from core-shell to Janus or inversed core-shell, in which PBTPA-shell surrounded PMMA-core, depending on the molecular weight of PBTPA segment in PBTPA-b-PMMA. When the molecular weight of PMMA segment was higher than that of PMMA homopolymer, watermelon-like particles in which small PBTPA domain less than 80 nm dispersed in the PMMA domain surrounded by PBTPA shell were observed. As the ratio of PBTPA-b-PMMA increased, the interface of the macrophase separation became obscure. At 50 wt% of the PBTPA-b-PMMA, only microphase separation was observed. The measurement of interfacial tension by pendant drop method demonstrated that PBTPA-b-PMMA lower the interfacial tension between PBTPA and the aqueous phase to the value similar to that of PMMA with the aqueous phase. (c) 2021 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences