Synthesis of poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) (PMMA-b-PNIPAM) amphiphilic diblock copolymer brushes on halloysite substrate via reverse ATRP

A series of well-defined copolymer brushes grafted from the halloysite substrate by reverse atom transfer radical polymerization (RATRP) were studied. A sufficient amount of peroxides as initiating moieties were firstly introduced onto the surface of halloysite substrate. Then the monomer methyl methacrylate (MMA) was polymerized via RATRP at a mild temperature using CuCl2 as a catalyst, 2,2′-bipyridine (bpy) as a ligand, and cyclohexanone as a solvent. The XPS and SPM results indicated that the PMMA chains grafted from the halloysite substrate. The kinetic studies revealed that there was a linear increase in Ln([M]0/[M]) with polymerization time. Moreover, the fact that the growth of N-isopropylacrylamide (PNIPAM) block from the PMMA-grafted halloysite (halloysite-g-PMMA) surface using the PMMA modified halloysite substrate as the macroinitiator provided further evidence of the existence of “living” chain ends in the halloysite-g-PMMA hybrid material.