Monte Carlo modelling of living branching copolymerisation of monovinyl and divinyl monomers: comparison of simulated and experimental data for ATRP copolymerisation of methacrylic monomers
Monte Carlo modelling of living branching copolymerisation of monovinyl and divinyl monomers: comparison of simulated and experimental data for ATRP copolymerisation of methacrylic monomers
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DOI：
10.1039/b901892a
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发表时间：
2009-01-01
期刊：
影响因子：
3.4
通讯作者：
Armes, Steven P.
中科院分区：
文献类型：
--
作者：
Bannister, Iveta;Billingham, Norman C.;Armes, Steven P.
用用C#编写的蒙特卡罗程序模拟了单乙烯基单体与少量二乙烯基单体在拟生存条件下的支化共聚反应。支化共聚物分子中的分子量、多分散性和主线性链的分布可以作为转化率的函数来模拟。通过为单乙烯基单体、未反应的二乙烯基单体和半反应的二乙烯基单体的双键反应指定不同的概率，可以模拟不同反应性的影响。将该蒙特卡罗模型的预测与以前获得的甲基丙烯酸2-羟丙酯和乙二醇二甲基丙烯酸酯的ATRP实验数据进行了比较(I.Bannister等人，Macromolecals，2006，39,7483-7492)。该模型预测了比实验实际观察到的更高的分子量和多分散性，这可能是因为在高转化率的实际反应中，支化成为扩散控制的，并且因为该模型允许链之间的耦合，而在真实体系中，链之间的耦合在空间上是受限的。该模型预测：(I)如果二乙烯基单体的比例很低，则会形成一定比例的残留线性伯链；(Ii)只有非常低水平的分子内(初级)环化才能形成环。实验和预测的相对分子质量与转化率数据的比较证实，实验确定的分子量快速上升的开始可以假设随机添加相同反应性的双键，从而导致统计支化和比传统自由基聚合获得的更均匀的结构。
Branching copolymerisation of a monovinyl monomer with a small amount of a divinyl monomer under pseudo-living conditions has been modelled using a Monte Carlo program written in C# code. Molecular weights, polydispersities and the distribution of primary linear chains amongst the branched copolymer molecules can be modelled as a function of conversion. The effect of varying reactivities can be modelled by assigning different probabilities for the reaction of the double bonds of the monovinyl monomer, the unreacted divinyl monomer and the half-reacted divinyl monomer. The predictions of this Monte Carlo model have been compared with experimental data previously obtained for the ATRP of 2-hydroxypropyl methacrylate with ethylene glycol dimethacrylate (I. Bannister et al., Macromolecules, 2006, 39, 7483-7492). The model predicts higher molecular weights and polydispersities than are actually observed experimentally, probably because branching becomes diffusion controlled in real reactions at high conversion and because the model allows couplings between chains which would be spatially constrained in the real system. The model predicts (i) formation of a proportion of residual linear primary chains if the proportion of divinyl monomer is low and (ii) only very low levels of intramolecular (primary) cyclisation to form loops. Comparison of experimental and predicted molecular weight vs. conversion data confirms that the experimentally determined onset of rapid molecular weight rise can be modelled assuming random addition of double bonds of equal reactivity, leading to statistical branching and more homogeneous structures than are obtained by conventional free-radical polymerisation.