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Physical Aging Investigations of a Spirobisindane-Locked Polymer of Intrinsic Microporosity
ACS Materials Letters ( IF 9.6 ) Pub Date : 2020-07-16 , DOI: 10.1021/acsmaterialslett.0c00184 Min Liu 1 , Xinxin Lu , Mitchell D. Nothling 1 , Cara M. Doherty 2 , Lianhai Zu 1 , Judy N. Hart , Paul A. Webley 1 , Jianyong Jin 3 , Qiang Fu 1, 4 , Greg G. Qiao 1
ACS Materials Letters ( IF 9.6 ) Pub Date : 2020-07-16 , DOI: 10.1021/acsmaterialslett.0c00184 Min Liu 1 , Xinxin Lu , Mitchell D. Nothling 1 , Cara M. Doherty 2 , Lianhai Zu 1 , Judy N. Hart , Paul A. Webley 1 , Jianyong Jin 3 , Qiang Fu 1, 4 , Greg G. Qiao 1
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Polymers of intrinsic microporosity (PIMs) have exceptional gas separation performance for a broad range of applications. However, PIMs are highly susceptible to physical aging, which drastically reduces their long-term performance over time. In this work, we leverage complementary experimental and density functional theory (DFT) studies to decipher the inter-/intrachain changes that occur during aging of the prototypical PIM-1 and its rigidified analogue PIM-C1. By elucidating this hereto unexplored aging behavior, we reveal that the dramatic decrease in gas permeability of PIM materials during aging stems from a loss of fractional free volume (FFV) due to PIM chain relaxations induced by π–π interactions, hydrogen bonding, or van der Waals’ forces. While the PIM-1 based membranes displayed enhanced gas pair selectivities after aging, the PIM-C1 based membranes showed an opposite trend with unexpected reductions for CO2/N2 and CO2/CH4. This is due to the reductions in CO2/N2 and CO2/CH4 solubility (S) selectivities and, unlike PIM-1, the spirobisindane locked PIM-C1 (i.e., maintenance of micropore sizes) has a stable diffusivity (D) selectivities that cannot offset such reductions. These fundamental insights into the intrinsic relaxation of different PIM polymer chains during physical aging can guide the future design of high-performance PIM materials with enhanced anti-aging properties.
中文翻译：
本征微孔的螺双茚满锁定聚合物的物理老化研究
具有固有微孔性（PIM）的聚合物具有出色的气体分离性能，适用于广泛的应用。但是，PIM极易受到物理老化的影响，随着时间的流逝，PIM的长期性能会大大降低。在这项工作中，我们利用互补的实验和密度泛函理论（DFT）研究来解密原型PIM-1及其刚性类似物PIM-C1老化期间发生的链间/链内变化。通过对此未阐明的老化行为进行说明，我们发现，在老化过程中，PIM材料的气体渗透率急剧下降是由于π–π引起的PIM链松弛导致的分数自由体积（FFV）损失所致。相互作用，氢键或范德华力。尽管基于PIM-1的膜在老化后显示出增强的气体对选择性，但基于PIM-C1的膜却显示出相反的趋势，CO 2 / N 2和CO 2 / CH 4出乎意料地降低。这是由于CO 2 / N 2和CO 2 / CH 4的溶解度（S）选择性降低，并且与PIM-1不同，螺双双茚满锁定的PIM-C1（即，维持微孔尺寸）具有稳定的扩散率（D）的选择性不能抵消这种减少。这些对物理老化过程中不同PIM聚合物链固有弛豫的基本见解可以指导未来具有增强抗老化性能的高性能PIM材料的设计。
更新日期：2020-08-03
中文翻译：
本征微孔的螺双茚满锁定聚合物的物理老化研究
具有固有微孔性（PIM）的聚合物具有出色的气体分离性能，适用于广泛的应用。但是，PIM极易受到物理老化的影响，随着时间的流逝，PIM的长期性能会大大降低。在这项工作中，我们利用互补的实验和密度泛函理论（DFT）研究来解密原型PIM-1及其刚性类似物PIM-C1老化期间发生的链间/链内变化。通过对此未阐明的老化行为进行说明，我们发现，在老化过程中，PIM材料的气体渗透率急剧下降是由于π–π引起的PIM链松弛导致的分数自由体积（FFV）损失所致。相互作用，氢键或范德华力。尽管基于PIM-1的膜在老化后显示出增强的气体对选择性，但基于PIM-C1的膜却显示出相反的趋势，CO 2 / N 2和CO 2 / CH 4出乎意料地降低。这是由于CO 2 / N 2和CO 2 / CH 4的溶解度（S）选择性降低，并且与PIM-1不同，螺双双茚满锁定的PIM-C1（即，维持微孔尺寸）具有稳定的扩散率（D）的选择性不能抵消这种减少。这些对物理老化过程中不同PIM聚合物链固有弛豫的基本见解可以指导未来具有增强抗老化性能的高性能PIM材料的设计。
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