Self-assembled core-shell and Janus microphase separated structures of polymer blends in aqueous solution

Abstract

Dissipative particle dynamics simulations are performed to systematically investigate the effects of hydrophobicity and compatibility on the inner phase separated structures (core-shell type or Janus type) of polymer nanoparticles self-assembled from a series of polymer blends in aqueous solution. Moreover, the temperature-dependent core-shell-to-Janus phase transition of a thermo-sensitive polymer blend is captured and explored by dissipative particle dynamics simulations for the first time. Our simulations reveal that both hydrophobicity and compatibility among blended polymers and the solvent play important roles in controlling the inner structures (core-shell or Janus) of polymer blend nanoparticles in aqueous solution. The phase separated structures of the studied polymer blend nanoparticles can be well predicted by using the criteria based on Neumann's triangle concept, which is derived from the corresponding interfacial tensions among the polymers and water. Besides, it was found that the hydrophobicity change of the blended thermo-responsive block copolymer induced by temperature plays a major role in the reversible transition from core-shell structure to Janus structure of the thermo-sensitive polymer blend nanoparticles. The present work is expected to provide some guidelines for designing and preparing novel polymer nanoparticles with desired structures and facilitating their applications in switching devices, nano-sensors, drug delivery system, etc.