A series of vinyl-addition poly(5-alkyl-2-norbornenes) with varied alkyl side group from methyl to tetradecyl was synthesized and systematically studied in terms of pure and mixed gas permeability. It was found that the length of the side group plays a key role in the gas separation performance. For instance, the permeability of permanent gases through these polymers changed non-linearly with the size of alkyl groups and the highest gas permeability was achieved for the polymers with short side-alkyl groups. Interestingly, a traditional trade-off between gas permeability and selectivity was not observed: vinyl-addition polynorbornene with methyl groups displayed both higher CO₂ permeability and higher CO₂/CH₄ selectivity. The solubility-controlled permeability of hydrocarbons is another feature of these polymers, which is unusual for low free-volume and silicon-free glassy polymers. According to the results of the pure gas permeability study, this feature was realized for all investigated polymers with short and long alkyl-side groups. However, the study of mixed gas permeability through these polymers showed that truly solubility-controlled permeability of hydrocarbons appeared only for the polymers bearing alkyl-substituents larger than ethyl-groups and therefore it is possible to switch on/off this feature for vinyl-addition poly(5-alkyl-2-norbornenes) by the choice of the size of alkyl groups. The obtained results are considered and discussed along with WAXD data and free volume fraction in these polymers.

合成了一系列具有从甲基到十四烷基的不同烷基侧基的乙烯基加成聚（5-烷基-2-降冰片烯），并在纯气体和混合气体渗透率方面进行了系统研究。发现侧基的长度对气体分离性能起关键作用。例如，永久气体通过这些聚合物的渗透率随烷基的大小呈非线性变化，具有短侧烷基的聚合物的气体渗透率最高。有趣的是，没有观察到气体渗透率和选择性之间的传统权衡：具有甲基的乙烯基加成聚降冰片烯显示出更高的 CO ₂渗透率和更高的 CO ₂ /CH ₄选择性。碳氢化合物的溶解度控制渗透性是这些聚合物的另一个特征，这对于低自由体积和无硅玻璃聚合物来说是不寻常的。根据纯气体渗透率研究的结果，所有研究的具有短和长烷基侧基的聚合物都实现了这一特征。然而，对通过这些聚合物的混合气体渗透率的研究表明，只有带有大于乙基基团的烷基取代基的聚合物才出现真正溶解度控制的烃渗透率，因此可以打开/关闭此功能以进行乙烯基加成聚（5-烷基-2-降冰片烯）通过选择烷基的大小。所获得的结果与这些聚合物中的 WAXD 数据和自由体积分数一起考虑和讨论。