Please use this identifier to cite or link to this item: https://doi.org/10.1016/j.polymer.2011.08.043
Title: The evolution of poly(hydroxyamide amic acid) to poly(benzoxazole) via stepwise thermal cyclization: Structural changes and gas transport properties
Authors: Wang, H. 
Liu, S. 
Chung, T.-S. 
Chen, H.
Jean, Y.-C.
Pramoda, K.P.
Keywords: Gas permeation properties
Poly(hydroxyamide amic acid)
Thermal rearrangement
Issue Date: 13-Oct-2011
Source: Wang, H., Liu, S., Chung, T.-S., Chen, H., Jean, Y.-C., Pramoda, K.P. (2011-10-13). The evolution of poly(hydroxyamide amic acid) to poly(benzoxazole) via stepwise thermal cyclization: Structural changes and gas transport properties. Polymer 52 (22) : 5127-5138. ScholarBank@NUS Repository. https://doi.org/10.1016/j.polymer.2011.08.043
Abstract: 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 CO2 permeability 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. © 2011 Elsevier Ltd. All rights reserved.
Source Title: Polymer
URI: http://scholarbank.nus.edu.sg/handle/10635/90340
ISSN: 00323861
DOI: 10.1016/j.polymer.2011.08.043
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