A new class of aromatic polyimides has been identified as a viable membrane material for separation processes requiring high permeability and selectivity with intrinsic thermal and chemical resistance properties.  The membranes are cast from soluble aromatic polyimides containing ortho-positioned functional groups;  exposure of the polyimides to thermal rearrangement at temperatures above Tg leads to the formation of polybenzoxazoles (PBO's) with exceptional performance for gas separations.  In this study, we examine the dynamic relaxation properties of the API polymers as a function of backbone structure and degree of thermal rearrangement.  Dynamic mechanical analysis and broadband dielectric spectroscopy are used to elucidate the sub-glass and glass-rubber relaxation characteristics of the polymers as related to their structural details and thermal exposure history. The information obtained provides insight as to the thermal resistance properties of the membranes, their local relaxation environment, and the influence of thermal rearrangement on segmental mobility and ultimate separation performance.

Structure and relaxation properties of thermally-modified aromatic polyimides for selective membrane separations

244th National Meeting (2012)

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