Conformation And Sensitivity Studies Of Polymer Brush Grafted From Inorganic Surface Via SI-ATRP

Polymer brush is a kind of special polymer material which high-density polymer chains were graftd on the surface of substrate, and has important application in the field of optical components, smart materials and biomedicine. In this paper, poly(methyl methacrylate)(PMMA) and poly(2-(dimethylamino)ethyl methacrylate)(PDMAEMA) brushes on the surface of silica particles and silicon wafers were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP).Firstly, PMMA-g-SiO2brushes were successfully synthesized via SI-ATRP, the results indicate that PMMA grafted on silica particles has better thermal stability than pure polymer, and polymer molecular weight decreased with the increasing initiator concentration which means the polymerization can be controlled by initiator. Also the effects of CuBr/PMDETA and CuCl/HMTETA catalyst systems to the conformation of PMMA-g-Si brush were investigated. It was found that CuCl/HMTETA system was more suitable than CuBr/PMDETA to control the "living" polymerization of PMMA chains, while better linear control by the initiator concentration on the thickness of PMMA brushes had been achieved under CuBr/PMDETA system.The same technological route was used to synthesize PDMAEMA-g-SiO2and PDMAEMA-g-Si brushes, and which the pH/temperature sensitive behaviors were investigated. When the pH of solution is lower than dissociation constant of polymer, the free PDMAEMA chains were stretched. Whereas, polymer chains shrink, and their lower critical solution temperature decreases with the increasing pH. Also, the equilibrium swelling ratio of PDMAEMA and PDMAEMA-g-SiO2is reduced with the increase of both pH and temperatures. Ralative to the original silica particles, the Cr(Ⅵ) adsorption in aqueous solution of PDMAEMA-g-SiO2was developed, which the maximum amount of adsorption is52.4mg/g (pH=3), and the amount of adsorption capacity reduced with the increasing pH successively. In addition, the thickness of resultant PDMAEMA-g-Si was controlled by the initator concentration, and brush is hydrophilic in acidic solution but hydrophobic in neutral or alkaline solution, which means that PDMAEMA-g-Si has pH sensitive behavior.