Preparation of high molecular weight PVA by emulsifier-free emulsion polymerization

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 emulsifiter-free emulsion polymerization at room temperature (14-20°C). 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.