Surface Modification Of Cellulose-based Materials By Graft Copolymerization Of ARGET ATRP

Cellulose is the most abundant biomass material in nature, and possesses some promising properties, such as mechanical robustness, renewability, biocompatibility, and biodegradability. However, it lacks some of the versatile properties of synthetic polymers and surface modification is always needed. In this thesis, surface modification of cellulose microspheres and filter papers via ARGET ATRP(activators regenerated by electron transfer atom transfer radical polymerization)was demonstrated. The resulting materials have both advantages of natural polymers and synthetic polymers, which provides new methods for preparing novel cellulose-based materials. This work can be summarized as follows:(1) ARGET ATRP was used to graft methyl methacrylate(MMA) from cellulose microspheres. The free polymer PMMA, formed from the sacrificial initiator in parallel to the grafting, was characterized by GPC, showing that the molecular weight of PMMA increased with increasing reaction time and the molecular weight distribution was narrow(Mw/Mn < 1.03). The cellulose microspheres before and after grafting were characterized by FT-IR, XPS, SEM and TGA.(2) Novel thermo-responsive cellulose surfaces have been achieved by grafting poly(N-isopropylacrylamide)(PNIPAM) from the filter papers via ARGET ATRP. Several solvents were tried to perform the reaction and 2-propanol/H2 O was proved to be the best one for the graft-copolymerization because the paper was kept undivided during the reaction in this solvent. The polymerization rate decreased successfully and modified papers with various graft ratios were achieved by adding a fewer amount of reducing agent intermittently, rather than an excess amount of reducing agent totally added before the reaction, which leads the polymerization to be very fast. The grafted cellulose presented a thermo-responsive character, with changes in wettability from hydrophilic at room temperature to hydrophobic at high temperature, and thes witching was reversible. The thermo-responsive property was evaluated by static water contact angle and the hydrophobicity of the grafted papers with different graft ratios was compared.(3) Novel pH-responsive cellulose surfaces were prepared via grafting poly(2-(dimethylamino)ethyl methacrylate) from the filter papers by ARGET ATRP. The free polymer, formed from the sacrificial initiator in parallel to the grafting, was characterized by GPC to investigate the molecular weight and molecular weight distribution of the grafted polymer chains. The grafted papers were evaluated with FTIR, SEM and graft ratio, suggesting that the grafting polymerization got a good control and the amount of polymer on the surfaces could be tailored by reaction time. Water contact angle measurements showed that the wettability of the grafted papers varied with changes in pH, and the hydrophobic ability was enhanced when the pH was improved.