Comparison of gas transport and sorption in the ladder polymer BBL and some semi-ladder polymers

Gas separation membrane permselectivity is often improved by the introducti on of stiffer polymeric backbone structures. This chain rigidity enables th e polymeric segments to discriminate more selectively between penetrants of different size. Although not extensively reported in the literature, ladde r and semi-ladder polymers formed from tetraamines and dianhydrides potenti ally provide rigid polymeric structures void of significant rotational mobi lity. This work examines the gas transport and sorption properties of BBL, a ladder polymer synthesized from 1,2,4,5-tetraaminobenzene tetrahydrochlor ide and 1,4,5,8-naphthalenetetracarboxylic acid. In addition, the behavior of He, CO2, O-2, N-2, and CH4 permeability, diffusion, and sorption coeffic ients with temperature is examined and shown to follow the Arrhenius and va n't Hoff relationships. The near-ambient permeation properties of BBL are a lso compared with other previously reported semi-ladder polymers formed usi ng polypyrrolone chemistry. These semi-ladder polymers incorporate both fla t, packable monomers such as those used to form BBL as well as bulky monome rs to inhibit chain packing. (C) 1999 Elsevier Science Ltd. All rights rese rved.