Temperature and pH Double Responsive Hybrid Cross-Linked Micelles Based on P(NIPAAm-co-MPMA)-b-P(DEA): RAFT Synthesis and “Schizophrenic” Micellization

Abstract

Poly(N-isopropylacrylamide-co-3-(trimethoxysilyl)propyl methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate) (P(NIPAAm-co-MPMA)-b-P(DEA)) copolymer was synthesized by reversible addition−fragmentation chain transfer (RAFT) polymerization. The temperature and pH responsive schizophrenic micellization behaviors of P(NIPAAm-co-MPMA)-b-P(DEA) and the cross-linking of P(NIPAAm-co-MPMA) blocks using inorganic silica-based cross-linking strategy were investigated in detail. Transmission electron microscopy (TEM) showed that the resultant core cross-linked (CCL) and shell cross-linked (SCL) micelles displayed regular spherical shapes with different sizes in N,N′-dimethylformamide (DMF) and aqueous media. The structure changes of CCL and SCL micelles at different pHs and temperatures were characterized by 1H NMR. Optical absorption measurements showed that the lower critical solution temperatures (LCSTs) of the CCL and SCL micelles were 37.5 and 40.5 °C, respectively. In vitro drug release study showed that th...