Vesicles Prepared from Supramolecular Block Copolymers

Polymeric vesicles were prepared through self-assembly of amphiphilic supramolecular block copolymers (SBP). Hydrophilic poly(N-isopropylacrylamide) with amino end groups (PNIPAM-NH₂) and hydrophobic polystyrene with carboxylic end groups (PSt-COOH) were prepared by free radical polymerization using cysteamine hydrochloride and thioglycolic acid as chain transfer reagents, respectively. These two polymer chains could be connected through the ionic interaction of the amino groups and carboxylic groups in dioxane to form an amphiphilic SBP. The self-assembly behavior of SBP was investigated in dioxane/H₂O and dioxane/ethanol systems. In the dioxane/H₂O system, these amphiphilic SBP could self-assemble to form spherical vesicles. In the dioxane/ethanol system, the morphologies of the formed aggregates were dependent on the SBP concentration. As the SBP concentration increased from 0.01 to 0.075 g mL⁻¹, the aggregates changed from wormlike vesicles to spherical vesicles. A temperature-induced morphological transition was observed in the dioxane/ethanol system. Increasing the temperature of the wormlike vesicular solution led to the transformation of the aggregates from wormlike vesicles to spherical vesicles.