Unique Self-Assembly of Sequence-Controlled Amino Acid Derived Vinyl Polymer with Gradient Thermoresponsiveness along a Chain.

A novel water-soluble amino acid derived vinyl polymer whose block sequence was designed to achieve a gradient thermoresponsiveness along a chain was accurately prepared through an ultrarapid reversible addition-fragmentation chain-transfer polymerization. The polymer exhibited unique temperature-regulated self-assembly in water, leading to multiple nanostructural transformations including disassembly-to-ordered and ordered-to-ordered transitions. The morphologies were drastically changed by heating the solution from 4 °C (soluble form) to 20 °C (spherical micelle) to 70 °C (vesicle). Moreover, such transitions exhibited hysteresis upon cooling, namely, from 70 °C (vesicle) to 20 °C (wormlike micelle) to 4 °C (soluble form). In this polymer system, the specific monomer sequence contributed to the self-assembly behavior. These findings provide significant insight into the design of new thermoresponsive nanomaterials with potential applications in biomedical chemistry.