无乳化剂乳液聚合制备高分子量聚乙烯醇

Preparation of High Molecular Weight PVA by Emulsifier-free Emulsion Polymerization

通过无乳化剂乳液聚合方法，采用氧化还原引发体系制备了超高分子量的聚醋酸乙烯酯（PVAc），继而醇解为超高分子量的聚乙烯醇（PVA）．研究了聚合温度、引发剂浓度、单体转化率对PVA的分子量和分子结构的影响．探讨了线性高分子量PVA结构的控制方法．结果表明，利用无乳化剂乳液聚合可以实现在室温（14～20℃）制备出聚合度为9899的高分子量的PVA，聚合过程对PVA的分子量和结构均有显著的影响．在无乳化剂乳液聚合恒速聚合区得到的聚合物分子量较高，分子量分布窄，且结构比较规整，而在加速区，PVAc的支化和交联现象显著，最终会对PVA的线性程度产生很大影响．因此，可以通过聚合过程来控制PVA的分子量和链结构．

The high molecular weight PVAc was prepared via an emulsifier-free emulsion polymerization, by using redox initiator system. The PVAc was then hydrolyzed to high molecular weight PVA. The influence of polymerization condition on molecular weight and distribution of PVAc is studied, such as the polymerization temperature, initiator concentration and conversion of monomer. The control method of structure of linear high molecular weight PVA is discussed. The results show that the PVA with DP = 9899 can be gotten via the emul- sifiter-free emulsion polymerization at room temperature （ 14--20℃）. The polymerization process has notable influence on the molecular weight and structure of PVA. The high molecular weight PVA with narrow distribution and orderly structure is obtained in constant velocity period of polymerization, while the branching and cross linkage of PVA become prominence during acceleration period, causing a bad effect on linear degree of PVA. Therefore, the control of molecular weight and chain structure of PVA can be achieved by manipulating polymerization process.