Control of Branching Vs. Cross‐Linking in Conventional Free Radical Copolymerization of MMA and EGDMA Using CoBF as a Catalytic Chain Transfer Agent
Control of Branching Vs. Cross‐Linking in Conventional Free Radical Copolymerization of MMA and EGDMA Using CoBF as a Catalytic Chain Transfer Agent
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使用 CoBF 作为催化链转移剂控制 MMA 和 EGDMA 传统自由基共聚中的支化与交联
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发表时间：
2005
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通讯作者：
G. Saunders
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作者：
S. Camerlynck;P. A. Cormack;D. Sherrington;G. Saunders
以钴肟（CoBF）为链转移催化剂，采用自由基溶液聚合法合成了甲基丙烯酸甲酯（MMA）和乙二醇二甲基丙烯酸酯（EGDMA），并以高转化率合成了完全可溶的支化聚甲基丙烯酸甲酯。使用8-32 ppm的CoBF水平，MMA/EGDMA的摩尔比高达100/10可用于生产支化产物，而没有任何大凝胶化或微凝胶形成。更高水平的EGDMA需要更高水平的CoBF来抑制交联，但反应难以控制且重现性差。1H NMR分析证实EGDMA以与共聚单体进料相当的水平掺入，并且这些残基中的通常50-70%作为支化链段而不是作为侧链部分反应的残基存在。已使用双检测（DD）和三检测（TD）尺寸排阻色谱（SEC）来评估产物的摩尔质量和支化特性。从这两个仪器的摩尔质量数据显示出良好的一致性，和产品的摩尔质量分布曲线非常相似，以前的产品制备使用十二烷硫醇（DDT）作为化学计量的链转移剂可以产生。然而，使用CoBF可以掺入的EGDMA的最大水平低于使用DDT时的情况。来自TDSEC仪器的分析数据允许逐片生成特性粘度（IV）数据和跨摩尔质量分布的Zimm支化因子g′的相应数据。在130，000 g/mol的给定摩尔质量下，g′与聚合进料中使用的EGDMA的水平很好地相关，并且与显示该支化共聚单体的有效掺入的1H NMR数据一致。献给约翰·L。斯坦福大学在他60岁生日之际。
Solution copolymerization of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) by conventional free radical methodology using a cobalt oxime (CoBF) as a catalytic chain transfer agent allows synthesis at high conversion of fully soluble branched poly (methyl methacrylate)s. Using CoBF levels of 8–32 ppm, mole ratios of MMA/EGDMA up to ∼100/10 can be employed in producing branched products without any macrogelation or microgel formation. Higher levels of EGDMA require higher levels of CoBF to inhibit cross‐linking, but the reactions are difficult to control and have poor reproducibility. An 1H NMR analysis confirms the incorporation of EGDMA at a level comparable to that of the comonomer feed and typically 50–70% of these residues are present as branching segments rather than as pendent partially reacted residues. Double detection (DD) and triple detection (TD) size exclusion chromatographs (SEC) have been used to evaluate the molar mass and branching character of the products. Molar mass data from both instruments show good agreement, and products with molar mass distribution curves very similar to those of previous products prepared using dodecanethiol (DDT) as a stoichiometric chain transfer agent can be produced. The maximum level of EGDMA that can be incorporated using CoBF is, however, lower than is the case when DDT is used. The analytical data from the TDSEC instrument allows the slice‐by‐slice generation of intrinsic viscosity (IV) data and corresponding data for the Zimm branching factor, g′, across the molar mass distribution. At a given molar mass of 130,000 g/mol, g′ correlates well with the level of EGDMA used in the polymerization feed, and is consistent with the 1H NMR data showing efficient incorporation of this branching comonomer. Dedicated to Professor John L. Stanford on the occasion of his 60th birthday.