Abstract The impact of double bond modification by gem-difluorocyclopropanation (gDFC) in poly(norbornenes) backbone on their gas transport properties was studied for the first time. With this aim the research of gDFC of polynorbornene (PNB) and poly(5-trimethylsilylnorbornene) (PNBSi) in the conditions of sodium chlorodifluoroacetate thermolyses at 180–190 °C in methyl benzoate solution were carried out. The starting poly(norbornenes) were synthesized via ring-opening metathesis polymerization of the corresponding monomers mediated by the first generation Grubbs’ catalyst. The degree of double bonds conversion into the gem-difluorocyclopropane and the molecular weight of modified polymers could be controlled by adjusting the reaction time, sodium chlorodifluoroacetate amount, and polymer concentration in reaction mixture, as well as by addition of inhibitor. The bulky Me3Si-substituent hindered the modification of double bonds in poly(norbornenes)’ backbone. The gDFC decreased the thermal stability of poly(norbornenes). However, the films of modified polymers demonstrated high stability during storage at the ambient conditions, especially in comparison with unmodified polynorbornene. The introduction of gem-difluorocyclopropane in poly(norbornenes) backbone increased their gas permeability coefficients P especially strongly for PNB. Simultaneously the values of ideal selectivity αij = Pi/Pj were not changed or slightly increased. The noted growth of P was caused by increases in the solubility coefficients S. To elucidate the role of the two types of modification fragment ( CF2 and O ) of double bonds a sample was prepared that included both types of the fragments. It was distinguished by increased P and αij values. So, a new and simple approach improving the gas permeation properties of metathesis polynorbornenes was developed. It may be extendable to broader families of polydienes and other polymers containing double bonds in the backbone.

中文翻译：

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一种提高复分解聚降冰片烯气体渗透性能的新方法：主链双键的墒-二氟环丙烷化

摘要 首次研究了聚（降冰片烯）骨架中墒二氟环丙烷化（gDFC）双键改性对其气体传输性能的影响。为此，在氯二氟乙酸钠在 180–190 °C 的苯甲酸甲酯溶液中热解条件下，对聚降冰片烯 (PNB) 和聚 (5-三甲基甲硅烷基降冰片烯) (PNBSi) 的 gDFC 进行了研究。起始聚（降冰片烯）是通过相应单体的开环复分解聚合合成的，由第一代格鲁布斯催化剂介导。双键转化为偕二氟环丙烷的程度和改性聚合物的分子量可以通过调节反应时间、氯二氟乙酸钠用量和聚合物在反应混合物中的浓度来控制，以及通过添加抑制剂。庞大的 Me3Si 取代基阻碍了聚（降冰片烯）主链中双键的修饰。gDFC 降低了聚（降冰片烯）的热稳定性。然而，改性聚合物的薄膜在环境条件下储存期间表现出高稳定性，特别是与未改性的聚降冰片烯相比。在聚（降冰片烯）主链中引入偕二氟环丙烷增加了它们的气体渗透系数 P，尤其是对于 PNB。同时，理想选择性值αij = Pi/Pj 没有改变或略有增加。P 的显着增长是由溶解度系数 S 的增加引起的。为了阐明两种类型的双键修饰片段（CF2 和 O）的作用，制备了包含这两种类型片段的样品。它通过增加的 P 和 αij 值来区分。因此，开发了一种改进复分解聚降冰片烯气体渗透性能的新的简单方法。它可以扩展到更广泛的聚二烯和其他主链中含有双键的聚合物。