# Toward Thermally Stimuli-Responsive Polymeric Vesicles Fabricated by Block Copolymer Blends for Nanocarriers

## TL;DR

Researchers developed temperature-sensitive nanoscale polymeric vesicles that can be used as drug or enzyme carriers, formed by mixing block copolymers in water.

## Contribution

A novel method for fabricating unilamellar polymeric vesicles via block copolymer blending with thermal responsiveness.

## Key findings

- Unilamellar polymeric vesicles under 50 nm were spontaneously formed by mixing block copolymers in water.
- The self-assembly into vesicles or micelles depends on temperature and mixing ratios of the copolymers.
- The phase transition temperature from micelles to vesicles can be tuned by adjusting copolymer concentrations.

## Abstract

Polymeric vesicles, characterized by enhanced colloidal stability, excellent mechanical properties, controllable surface functionality, and adjustable membrane thickness, are extremely useful in nano- and bio-technology for potential applications as nanosized carriers for drugs and enzymes. However, a few preparative steps are necessary to achieve a unilamellar vesicle with a narrow size distribution. Herein, we report the spontaneous formation of unilamellar polymeric vesicles with nanometer sizes (<50 nm), fabricated by simply mixing diblock copolymers (P(EO-AGE)(2K-2K) and P(EO-AGE)(0.75K-2K)) with differing hydrophilic mass fractions in aqueous solutions. Depending on the mixing ratio of block copolymers and the temperature, the block copolymer mixtures self-assemble into various nanostructures, such as spherical and cylindrical micelles, or vesicles. The self-assembled structures of the block copolymer mixtures were characterized by small-angle neutron scattering, resulting in a phase diagram drawn as a function of temperature and the mixing condition. Notably, the critical temperature for the micelle-to-vesicle phase transition can be easily controlled by altering the mixing conditions; it decreases with an increase in the concentration of one of the block copolymers.