使用差示扫描量热(DSC)、萃取/平衡溶胀和动态力学分析(DMA)研究了双硫酯结构对二甲基丙烯酸酯可逆加成-断裂链转移(RAFT)自由基聚合速率、凝胶行为和交联结构的影响.聚合速率取决于双硫酯Z基团的稳定作用,Z基团为苯基时聚合速率最慢,Z基团为环己基时聚合速率最快;二硫代苯甲酸苄酯(BDB)中Z基团的强稳定作用使中间态自由基浓度增大,中间态自由基的双基终止导致凝胶点提前;环己基二硫代甲酸苄酯(BCDC)中Z基团的弱稳定作用使反应控制能力下降,不利于交联网络的均匀性.
Three dithioesters with different Z-moieties were used as chain transfer agents in the reversible addition-fraction chain transfer (RAFT) radical polymerization of dimethacrylates in order to investigate the effect of dithioester structure on the kinetics, gelation and network structure. The polymerization rate was monitored with differential scanning calorimetry (DSC), the gelation and the network structure was measured by solvent extraction/ swelling and dynamic mechanical analysis (DMA). The polymerization rate increased due to the increased propagating radical concentration when phenyl Z-group in benzyl dithiobenzoate (BDB) was replaced by benzyl in benzyl phenyldithioacetate (BPDA) or cyclohexyl group in benzyl cyclohexanedithiocarboxylate (BCDC). The stabilizing effect of phenyl in BDB induced a certain extent of irreversible termination between intermediate radicals, resulting in an earlier gelation and higher crosslinking density. The RAFT mediated by BCDC with eyclohexyl as Z-group showed weaker controlling capability over the reaction, generating a polymer with less homogenous network.
参考文献
| [1] | Yu Q;Zhu YS;Ding YH;Zhu SP .Reaction behavior and network development in RAFT radical polymerization of dimethacrylates[J].Macromolecular chemistry and physics,2008(5):551-556. |
| [2] | Barner-Kowollik C;Buback M;Charleux B;Coote ML;Drache M;Fukuda T;Goto A;Klumperman B;Lowe AB;Mcleary JB .Mechanism and kinetics of dithiobenzoate-mediated RAFT polymerization. I. The current situation[J].Journal of Polymer Science, Part A. Polymer Chemistry,2006(20):5809-5831. |
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