Surface Functionalization of Chitosan Nanospheres via Surface-Initiated AGET ATRP Mediated by Iron Catalyst in the Presence of Limited Amounts of Air

A novel method of surface modification of solids was first developed via iron(III)-mediated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) on the surfaces of chitosan nanospheres (CTSNSs) with an average diameter of 80 nm using FeCl3 center dot 6H(2)O as the catalyst, PPh3 as the ligand, and ascorbic acid (VC) as the reducing agent in the presence of it limited amount of air. The homopolymer poly(methyl methacrylate) (PMMA) and amphiphilic block copolymer poly(methyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PMMA-b-P(PEGMA)) were grafted onto the surfaces of the CTSNSs. Well-defined polymer chains were grown front the CTSNS surfaces to yield individual nanospheres composed of a chitosan core and a well-defined, densely grafted outer PMMA or PMMA-b-P(PEGMA) layer. The kinetics of surface-initiated AGET ATRP of MMA in the presence of a limited amount of air was investigated. A linear kinetic plot for the homopolymer, linear increase of molecular weight (M-n) with conversion, and linear plot of grafted percentage verse time were observed. The chemical composition of the nanosphere surfaces at different surface modification stages was validated by Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS).