Study Of Photoinitiated Solution/Precipitation Polymerization Of Acrylamide

The typical characteristic of photo-polymerization lies in that it can be carried out at low temperature with high reaction rate, simple equipment and strong practicability. The key aim of this thesis is to do research in photo-initiated solution polymerization and precipitation polymerization of acrylamide.Firstly, the thesis studied photo-initiated solution polymerization of acrylamide. The principle of this study is that light intensity attenuates with the increasing of distance to the light-source because of the self-shield effect, so the photo-initiator with the same concentration irradiated by UV light of different intensity creates a free radical concentration gradient along the light irradiation direction. The low-voltage Hg lamp and ITX/EDAB were respectively employed as light-source and initiator to prepare high molecular weight polyacrylamide (PAM). The experimental results indicated that a gradient effect really exists within the free radical polymerizing system of acrylamide (AM) water solution, that is, the molecular weight increases while the conversion decreases along the UV light irradiation direction. The highest molecular weight of homopolymer of AM obtained is 27 million. The factors influencing the molecular weight of gradient polymerization initiated by UV of AM water solution and reasons for the gel forming of PAM were investigated. The molecular weight of PAM can increase effectively by prolonging reaction time and increasing layer thickness. Decreasing reaction temperature and increasing monomer concentration cause the increase of molecular weight, especially the layer farther from light source. Decreasing initiator concentration brings the increase of molecular weight as well as the increase of molecular weight gradient. The decrease of monomer concentration, increase of initiator concentration, reduction of reaction time and increase of reaction temperature can decrease the gel content of product.Then, using 8W low pressure mercury lamp as light source, 1-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1 -propane-1 -one (Irgacure 2959) as main photoinitiator, and acetone/H₂O as main solvent, the precipitation polymerization of acrylamide has been studied. The result shows that, the reaction rate of photo-initiated precipitation is high with no inducement time. The proportion of acetone to water has obvious influence on the product, that is, partly cross-linked and poor water-soluble PAM was obtained when the water content is higher than 10 % while dusty PAM was obtained when that is lower than 10%. With the decrease of water content, the gel content as well as the molecular weight decrease. The molecular weight of PAM increases with the increase of monomer concentration, decrease of initiator concentration and light intensity. The change of layer thickness has little influence of the molecular weight of PAM. Study of photo-initiated precipitation polymerization using ethyl acetate as medium shows that precipitation of polymer appears earlier with lower molecular weight and reaction rate compared with the system using acetone/water as the medium.