Surface Modification Of Wood Surface Via Activators Regenerated By Electron Transfer ATRP

Wood is characterized by hydrophilic and dimensional instabilities with moisture. Its dimensional stability can be improved considerably by converting hydrophilic OH-groups into hydrophobic groups. As the containing of carbohydrate of wood cell wall, it is vulnerable to be attacked by fungi and termites. The growing or loading of antibacterial materials on wood surface can reduce defects caused by fungi and termites. Atom Transfer Radical Polymerization (ATRP) is a "controlled" /living radical polymerization method. Varieties monomers have been grafted from the surface of cellulose and natural fibers. The invention of activators regenerated by electron transfer ATRP (ARGET ATRP) will facilitate its manufacturing application for it is more environmental friendly and easier accessibility. In this study, we modified wood surface by grafting monomers from it, and try to endow wood surface with many functionalities, to increase its service life and extend its applicability.This paper studied the grafting effect of three grafting processes (normal grafting process, sodium hydroxide treated wood and then graft initiator through normal grafting process, hot grafting process) that graft 2-bromoisobutyryl bromide from wood surface, and select hot grafting process to graft initiator in this paper. Furthermore, the influence of initiator concentration, reaction temperature and reaction time on grafting effect is also discussed in this paper. After the grafting of initiator, methyl methacrylate (MMA) was grafted via ARGET ATRP, glycidyl methacrylate (GMA) was grafted via ARGET ATRP followed by postmodificaiton with palmitoyl chloride to endow wood surface with hydrophobic.2-(Dimethylamino)ethyl methacrylate (DMAEMA) was grafted to endow wood surface with pH-sensitive property. Poly(2-(Dimethylamino)ethyl methacrylate) which grafted on wood surface was converted into quaternary ammonium salt after its quaternization by ethyl bromide, acrylic acid was grafted from wood surface and the silver anions embedded in the PAA brushes are reduced into Ag nanoparticles under the reduction of sodium borohydride (NaBH4), in order to produce antibacterial wood surface. Wood was characterized after surface modification, and the results are:(1) Methyl methacrylate (MMA) was grafted from wood surface via ARGET ATRP to endow wood surface with hydrophobic. The results of FTIR, SEM and TGA show that poly(methyl methacrylate)(PMMA) has been successfully grafted on wood surface via ARGET ATRP and its amount increased with reaction time. The result of contact angle shows that larger contact angle and longer contact angle stability time of wood surface were produced by the prolongation of grafting time.(2) Glycidyl methacrylate (GMA) was grafted from wood surface via ARGET ATRP followed by postmodificaiton with palmitoyl chloride to endow wood surface with hydrophobic. The results of FTIR, SEM and TGA show that poly(glycidyl methacrylate)(PGMA) has been successfully grafted on wood surface and palmitoyl chloride reacted with hydrolyzed PGMA-grafted wood surface. The amount of PGMA can be tailored by control the reaction time. The hydrophobic of wood surface is improved of this method compared to that of the method that palmitoyl chloride reacted with wood surface directly.(3) 2-(Dimethylamino)ethyl methacrylate (DMAEMA) was grafted to endow wood surface with pH-sensitive property. The results of FTIR, SEM and TGA show that Poly(2-(Dimethylamino)ethyl methacrylate) has been successfully grafted on wood surface, combined the result of XPS, we can know the grafted PDMAEMA on wood surface is thicker than the XPS detection thickness. When the pH of testing solution ranged from 2.21 to 13, the contact angle of wood surface has no obvious change. But after increasing the concentration of acidic solution and basic solution, wood surface shows different wettability:hydrophilic (acid solution) and hydrophobic (CA=128°, basic solution).(4) Poly(2-(Dimethylamino)ethyl methacrylate) grafted on wood surface was quaternized by ethyl bromide to endow wood surface with antibacterial property. The results of FTIR and SEM-EDX prove the success of the quaternization procedure. Antibacterial activity of the modified wood surface against E.coli was evaluated by using optical density method; the result shows that modified wood surface exhibit antibacterial activity against E.coli.(5) Tert-Butyl acrylate was grated from wood surface via ARGET ATRP, and then hydrolyze poly(tert-Butyl acrylate) to poly(acrylic acid), silver anions embedded in PAA brushes due to the numerous carboxyl group (-COOH), followed by the reduction process by sodium borohydride (NaBH4) to produce Ag nanoparticles in situ. The results of EDX and XRD show the Ag nanoparticles have loaded on wood surface successfully. The result of antibacterial detection shows that modified wood surface exhibit good antibacterial activity against E.coli.