甲基丙烯酸甲酯可逆加成-断裂链转移聚合动力学研究

Investigation on the kinetics of reversible addition-fragmentation chain transfer polymerization of methyl methacrylate

通过可逆加成-断裂链转移(RAFT)溶液聚合制得一系列分子量可控、分子量分布窄的聚甲基丙烯酸甲酯(PMMA),考察了反应条件对聚合速率、PMMA分子量及其分布的影响。实验结果表明,溶剂质量、聚合温度和引发剂浓度是影响聚合速率的主要因素,而RAFT试剂浓度和结构可调控PMMA的分子量及其分布。对于甲基丙烯酸甲酯体系,密度泛函理论的计算结果表明,RAFT试剂“激活”过程的Gibbs自由能变(ΔG)是评估RAFT试剂对聚合物分子量分布控制效果的关键因素。ΔG越小,表明RAFT试剂越容易被“激活”,控制效果越好。提出了一种快速判断RAFT试剂可行性的理论计算依据,降低了RAFT试剂的实验开发成本。

A series of polymethyl methacrylates(PMMA)with controlled molecular weights and narrow molecular weight distributions were synthesized by reversible addition-fragmentation chain transfer(RAFT)solution polymerization.The effects of reaction conditions on the rate of polymerization,molecular weight,and molecular weight distribution were investigated.The experiments identified the mass of the solvent,temperature,and initiator concentration as the main factors influencing the polymerization rate,while the concentration and structure of the RAFT agent mainly control the molecular weight and its weight distribution of the PMMA.Calculations performed using the density functional theory indicate that the Gibbs free energy change(ΔG)of the activation process of the RAFT agent is a key factor in controlling the molecular weight distribution during the methyl methacrylate polymerization.A smallerΔG value indicates that the RAFT agent is more easily activated,making it more effective in controlling the molecular weight distribution.The theoretical calculations can serve as an effective method for quickly evaluating the performance of RAFT agents,helping to lower the experimental cost.