【作者】 严艳；

【导师】 杨万泰；

【作者基本信息】 北京化工大学 ， 高分子化学与物理， 2007， 硕士

【摘要】 UV光引发聚合具有可在较低温度下进行，聚合反应速度快、设备简单、实用性强的特点。本课题的主要目的是对紫外光引发丙烯酰胺沉淀聚合以及水溶液聚合深入研究。首先，本论文研究了紫外光引发丙烯酰胺水溶液聚合。利用光强随着光程增加而逐渐减小的自屏蔽效应，不同光强引发相同浓度的光敏剂时必然造成一个沿着光辐射方向的自由基浓度梯度的原理，以低压汞灯为光源，以ITX/EDAB为光引发剂引发丙烯酰胺的自由基梯度聚合来制备高分子量聚丙烯酰胺。实验结果表明，紫外光引发丙烯酰胺水溶液自由基聚合体系确实存在沿光辐射方向的梯度效应，即分子量沿光辐射方向分子量逐渐增大，转化率则依次减小。得到的丙烯酰胺均聚物的最高分子量为两千七百万。同时考察了影响丙烯酰胺水溶液光引发梯度聚合分子量及聚丙烯酰胺成凝胶的因素，发现延长反应时间和增加液层厚度能有效的提高聚合产物的分子量。降低聚合反应温度和增大单体浓度可以增加分子量且远离光源处分子量变化尤其明显；降低引发剂浓度可以增大分子量分子量梯度效应增大；减小单体浓度、增大引发剂浓度、减少反应时间、提高反应温度均使聚丙烯酰胺凝胶含量降低。其次以8W低压汞灯作为光源，以1-[4-(2-羟乙氧基)-苯基]-2-羟基-2-甲基丙酮(Irgacure 2959)为光引发剂，以丙酮/水为主要溶剂，研究了不同反应条件下的紫外光引发丙烯酰胺沉淀聚合。结果显示：紫外光引发的AM沉淀聚合体系没有诱导期，反应速度快。体系中丙酮/水含量的比例对产物影响较大。当水含量大于10％时，得到部分交联但水溶性差的块状PAM。水含量小于10％时，得到粉末状的PAM。随着体系中水含量的减少，聚合产物凝胶含量降低，但分子量也随着降低。PAM分子量随着单体浓度的增加而增加，随引发剂浓度和光强的增加而降低。反应液层厚度对产物分子量的影响不大。论文还研究了乙酸乙酯为分散介质的丙烯酰胺沉淀聚合体系。结果表明，反应开始后聚合物更早的发生沉淀，聚合速率和产物分子量均低于丙酮/水复合分散体系。更多还原

【Abstract】 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.更多还原