Reversible Control of Primary and Secondary Self-Assembly of Poly(4-allyloxystyrene)-Block-Polystyrene

Abstract

The reversible control of primary and secondary self-assemblies was attained using a poly(4-allyloxystyrene)- block-polystyrene diblock copolymer (PASt- 𝑏 -PSt) through variations in temperature. The copolymer showed no self-assembly in cyclohexane over 3 5 ∘ C and existed as a unimer with a 37.1 nm hydrodynamic diameter. When the temperature was lowered to 3 0 ∘ C , the copolymer formed micelles with 269.9 nm by the primary self-assembly. As the result of further lowering the temperature to 2 0 ∘ C , the secondary self-assembly of the micelles occurred to produce ca. 2975.9 nm aggregates. The aggregates were dissociated into unimers by increasing the temperature up to 4 0 ∘ C . The light scattering studies demonstrated that the thermoresponsivity of the copolymer showed good hysteresis throughout the variation in the temperature in the range between 20 and 4 0 ∘ C , based on the Marquadt analysis of the hydrodynamic diameter distribution. It was found that the primary and secondary self-assemblies of the copolymer were perfectly controlled by the temperature.