The evolution of poly(hydroxyamide amic acid) to poly(benzoxazole) via stepwise thermal cyclization: Structural changes and gas transport properties
The evolution of poly(hydroxyamide amic acid) to poly(benzoxazole) via stepwise thermal cyclization: Structural changes and gas transport properties
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DOI：
10.1016/j.polymer.2011.08.043
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发表时间：
2011-10
期刊：
影响因子：
4.6
通讯作者：
Huan Wang;Songlin Liu;T. Chung;Hongmin Chen;Y. Jean;K. Pramoda
中科院分区：
文献类型：
--
作者：
Huan Wang;Songlin Liu;T. Chung;Hongmin Chen;Y. Jean;K. Pramoda
本文研究了一种用于气体分离的热重排（TR）材料的热致结构转变和高分子链重排。通过在400 °C下热环化2 h将原始的聚（羟基酰胺酰胺酸）（PHAA）转化为最终的聚苯并恶唑（PBO），实现了高达215倍的CO2渗透性的巨大增强。由2，2-双（3-氨基-4-羟基苯基）六氟丙烷（BisAPAF）和偏苯三酸酐氯化物（TAC）通过从130 °C至400 °C的热处理衍生的原始聚合物PHAA的演变已经通过各种表征技术包括元素分析、TGA、TGA-IR、DSC、ATR-FTIR、XPS、XRD和正电子湮没寿命光谱（帕尔斯）来检查。逐步环化过程开始于环化脱水，然后是环化脱羧。在第一步中，PHAA在高达300 °C下转化为聚（酰亚胺苯并恶唑）（PIBO），而在第二步中，PBO的最终结构在400 °C下形成。随着环化过程的变化，气体输运性质也呈现出阶梯式的变化。聚合物分子链间距和自由体积空腔半径的显著增大为从分子水平上理解气体输运性质的变化提供了基础。
The thermally induced structure transformation and polymer chain rearrangement of a thermally rearranged (TR) material for gas separation has been explored in this work. A tremendous enhancement as high as 215 folds in CO2permeability has been achieved by converting the pristine poly(hydroxyamide amic acid) (PHAA) to the final polybenzoxazole (PBO) via thermal cyclization at 400 °C for 2 h. The evolution of the pristine polymer PHAA derived from 2,2-bis(3-amino-4-hydroxyphenyl)hexafluropropane (BisAPAF) and trimellitic anhydride chloride (TAC) by thermal treatment from 130 °C to 400 °C has been examined by various characterization techniques including elemental analysis, TGA, TGA-IR, DSC, ATR-FTIR, XPS, XRD and Positron Annihilation Lifetime Spectroscopy (PALS). The stepwise cyclization process commences with cyclodehydration followed by cyclodecarboxylation. At the first step, PHAA transforms to poly(imide benzoxazole) (PIBO) up to 300 °C, while at the second step, the final structure of PBO is formed at 400 °C. Following the changes in the cyclization process, gas transport properties also show the stepwise changes. The significant enlargements of polymer inter-chain distance and free volume cavity radius provide the fundamental understanding for the changes of gas transport properties at the molecular level.