Polyion Complex Micelles Possessing Thermoresponsive Coronas and Their Covalent Core Stabilization via "Click" Chemistry

Two oppositely charged graft ionomers, P(MAA-co-AzPMA)-g-PNIPAM and P(QDMA-co-AzPMA)-g-PNIPAM, containing thermosensitive PNIPAM graft chains were successfully synthesized via a combination of atom transfer radical polymerization (ATRP) and “click” reactions, where PAzPMA, PMAA, PNIPAM, and PQDMA are poly(3-azidopropyl methacrylate), poly(methacrylic acid), poly(N-isopropylacrylamide), and poly(2-(dimethylamino)ethyl methacrylate) (PDMA) fully quaternized with methyl iodide, respectively. In aqueous solution, polyelectrolyte complexation between negatively charged backbone of P(MAA-co-AzPMA)-g-PNIPAM and positively charged backbone of P(QDMA-co-AzPMA)-g-PNIPAM leads to the formation of polyion complex (PIC) micelles consisting of polyion complex cores and thermoresponsive PNIPAM coronas. Upon addition of a difunctional cross-linker, propargy ether, PIC micelles can be facilely cross-linked via “click” reactions. The obtained covalently core-stabilized PIC micelles exhibit permanent stability against the a...