Gelation in Living Copolymerization of Monomer and Divinyl Cross-Linker: Comparison of ATRP Experiments with Monte Carlo Simulations
Gelation in Living Copolymerization of Monomer and Divinyl Cross-Linker: Comparison of ATRP Experiments with Monte Carlo Simulations
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DOI：
10.1021/ma901005d
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发表时间：
2009-08-25
期刊：
影响因子：
5.5
通讯作者：
Matyjaszewski, Krzysztof
中科院分区：
文献类型：
--
作者：
Gao, Haifeng;Polanowski, Piotr;Matyjaszewski, Krzysztof
进行了两种类型的蒙特卡罗模拟来模拟单乙烯基单体和二乙烯基交联剂的活性共聚中的凝胶化。将不同条件下的模拟凝胶点与一系列 ATRP 反应中获得的实验凝胶点以及基于 Flory-Stockmayer (FS) 理论计算的凝胶点进行比较。第一个模拟基于离格 (OL) 模型，通过忽略大分子的几何形状进行简化。第二个更复杂的模拟基于动态晶格液体（DLL）模型。 OL模型和FS平均场理论都能够考虑交联剂与引发剂的摩尔比和引发速率对凝胶点的影响。然而，与实验结果相比，模拟凝胶点发生在低得多的单体转化率下。此外，溶剂稀释度是调节实验凝胶点的重要参数，在OL模拟和FS理论中对凝胶点没有影响。相比之下，基于晶格上元素协同运动的 DLL 模拟成功预测了溶剂稀释对凝胶点的影响。在 DLL 系统中添加溶剂珠降低了引发剂、交联剂和单体的浓度，并显着推迟了凝胶点。降低主链的目标 DP，同时保持引发剂和交联剂的摩尔浓度恒定，也会导致凝胶化延迟，这一点已在类似条件下通过 ATRP 实验得到证实。这些结果提供了了解凝胶点对各种参数的依赖性的方法，并且可以作为开发更先进的受控/活性共聚系统模拟模型的基础。
Two types of Monte Carlo simulations were carried out to simulate gelation in a living copolymerization of monovinyl monomer and divinyl cross-linker. The simulated gel points under various conditions were compared to the experimental gel points obtained in series of ATRP reactions and the calculated gel points based on Flory-Stockmayer (FS) theory. The first simulation was based on an off-lattice (OL) model, simplified by ignoring the geometry of macromolecules. The second more complex simulation was based on the dynamic lattice liquid (DLL) model. Both OL model and FS mean-field theory were capable to count on the influence of molar ratios of cross-linker to initiator and initiation rate on the gel points. However, the simulated gel points occurred at much lower monomer conversion, as compared to the experimental results. Furthermore, the solvent dilution, an important parameter to adjust the experimental gel points, had no effect on the gel points in both OL simulation and FS theory. In contrast, the DLL simulation based on a cooperative motion of elements on a lattice successfully predicted the effect of solvent dilution on the gel points. Addition of solvent beads in the DLL system decreased the concentrations of initiator, cross-linker, and monomer and significantly postponed the gel points. A decreasing targeted DP of primary chains, while keeping the molar concentrations of initiator and cross-linker constant, also resulted in a delayed gelation, which was confirmed by the ATRP experiments under similar conditions. These results provide means to understand the dependence of gel points on various parameters and can serve as a basis for the development of more advanced simulation models of the controlled/living copolymerization systems.