甲基丙烯酸酯原子转移自由基交联聚合与网络密度

Atom Transfer Radical Crosslinking Polymerization of Methacrylates and Network Density

研究了甲基丙烯酸酯/二甲基丙烯酸酯原子转移自由基交联聚合体系中交联密度对其交联聚合行为的影响。研究发现,交联单体用量增加导致交联网络密度增大,过渡金属络合物的扩散受阻严重,从而使聚合速率和双键转化率都增加;交联体系的凝胶点随交联单体用量增加提前出现;交联网络中初级链分子量随转化率呈线性增长,但是在聚合后期发生偏离,偏离点所对应的转化率随交联单体用量的增加而降低。说明交联密度越高,越不利于保持原子转移自由基聚合的“活性”/控制能力。

The influence of crosslinking densities on the reaction behavior of atom transfer radical polymerization of methacrylate/dimethacrylate was studied. It was found that, with more dimethacrylate introduced, the crosslinking density increased, which put more restriction to the diffusion of transition metal complex, giving rise to a faster polymerization rate and a higher vinyl group conversion. The gel point also appeared earlier when more dimethacrylate was used. The molecular weight of the primary chains in the network increased linearly with vinyl group conversion, but deviated from this trend at higher conversions. The conversion corresponding to the deviation decreased with the increase of dimethacrylate content. It was demonstrated that the higher crosslinking densities would damage the ＂living＂ /controlled nature of ATRP in the network forming systems.