Construction of mixed micelle with cross-linked core and dual responsive shells

Abstract

A core cross-linked (CCL) mixed micelle with dual responsive shells was constructed from two amphiphilic block copolymers poly(methyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate)-b- poly(N-isopropylacrylamide) (P(MMA-co-MPMA)-b-PNIPAAm) and P(MMA-co-MPMA)-b-poly(2-(diethylamino)ethyl methacrylate) (P(MMA-co-MPMA)-b-PDEA) via a two-step process: cooperative aggregation of the two block copolymers into core-shell mixed micelles in acidic aqueous solution at room temperature followed by cross-linking of the hydrophobic core via an acid-catalyzed sol–gel process. The reversibly structural transformation of the core-shell mixed micelles into core-shell-corona (CSC) mixed micelles took place when subjected to elevated temperature or pH value, that is, high temperature resulted in the fabrication of CSC mixed micelle with shrunk PNIPAAm chains as the inner shell and stretched PDEA chains as the outer corona, and alkaline pH led to the formation of CSC mixed micelle with collapsed PDEA chains as the inner shell and extended PNIPAAm chains as the outer corona. Due to the existence of thermo- and pH- dually responsive shells, the structurally stable CCL mixed micelle may find practical applications in biomedical fields such as drug delivery and intelligent release.