Tert-butoxycarbonyl (t-BOC) is a thermally labile moiety that can be used to protect hydroxyl groups on polymers. In this study, t-BOC was appended onto a polyimide consisting of 2,2′-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 3,3′-dihydroxy-4,4′-diamino-biphenyl (HAB), after which the polymer was formed into self-standing films. Solid-state thermal treatments were performed to systematically remove t-BOC moieties to alter the physical packing structure and concomitant gas transport properties of the polymer. Despite performing deprotection reactions well below the glass transition temperature of 6FDA-HAB (∼300 °C), this free volume manipulation (FVM) approach produced only subtle differences in polymer density, fractional free volume, average free volume element size, and gas transport properties relative to the unprotected polymer. While these findings suggest that thermally removing covalently bound functional groups from polymer films can be used to manipulate free volume and gas transport performance for glassy polymers, more robust polymer systems than linear polyimides are required to preserve the nascent free volume architecture generated from this approach.

叔丁氧羰基（t-BOC）是热不稳定的部分，可用于保护聚合物上的羟基。在这项研究中，将t-BOC附加到由2,2'-双-（3,4-二羧基苯基）六氟丙烷二酐（6FDA）和3,3'-二羟基-4,4'-二氨基联苯（ HAB），然后将聚合物形成自立膜。进行固态热处理以系统地除去t-BOC部分，以改变聚合物的物理堆积结构和伴随的气体传输性质。尽管进行脱保护反应的温度远低于6FDA-HAB的玻璃化转变温度（〜300°C），但这种自由体积操纵（FVM）方法在聚合物密度，自由体积分数，平均自由体积元素尺寸，以及相对于未保护的聚合物的气体传输性能。尽管这些发现表明从聚合物薄膜中热去除共价键合的官能团可用于控制玻璃态聚合物的自由体积和气体传输性能，但仍需要比线性聚酰亚胺更坚固的聚合物体系来保持这种方法所产生的新生的自由体积结构。