Versatile thiolated thermosensitive polymers synthesized by ATRP of MEO2MA and AcSEMA, a new methacrylic monomer with a protected thiol group

Abstract

Herein, the synthesis of a new monomer containing a protected thiol group, 2-(acetylthio)ethyl methacrylate (AcSEMA), is introduced. The monomer has been copolymerized via atom transfer radical polymerization (ATRP) with 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) to obtain a series of well-defined hidden-thiol functionalized thermosensitive polymers. The new system exhibits a sharp lower critical solubility temperature (LCST) and after hydrolysis of the acetyl group, the thiolated copolymers exhibit pH responsiveness. Moreover, to show the versatility of AcSEMA, P(MEO₂MA-co-AcSEMA) copolymers were in situ hydrolyzed and modified by thiol-ene Michael addition with some acrylate compounds. The click reaction was successfully performed as revealed by NMR and the change in the LCST. We finally demonstrate that the addition of these polymer coatings onto gold nanoparticles (AuNPs) results in the formation of stable, colloidal thermosensitive polymer@AuNP complexes due to bridge formation between the thiol groups of AcSEMA and the metallic NP surfaces. The formation of temperature responsive polymer coated plasmonic nanoparticles shows the promise of P(MEO₂MA-co-AcSEMA) copolymers for building multifunctional nanostructures for drug-delivery, diagnosis, tagging, catalysis and organic electronics systems.