Effect on oxygen permeation properties

The structure of an amorphous polyamide prepared from hexamethylenediamine and isophthalic/tere-phthalic acids was modified in order to determine the effect of chemical structure on the oxygen permeation properties. The greatest increase in permeation was obtained by lengthening the aliphatic chain. Placement of substituents on the polymer chain also led to increased permeation. Reversal of the amide linkage direction had no effect on the permeation properties. Free volume calculations and dielectric relaxation studies indicate that free volume is probably the dominant factor in determining the permeation properties of these polymers. 

Effect of Chain Length. The initial part of this study consisted of determining the effect of aliphatic chain length on the permeation properties of the polyamides. A series of isophthal-amides (n-I) was prepared where the aliphatic chain length was systematically altered from 2 to 10 methylenes (5). Crystalline melting points were observed by DSC for 2-1 and 1-1, so permeation data was measured only for 4-1 through 10-1. The thermal, density, and oxygen permeation data for this series are contained in Table I. 

Through systematic modification of the polymer backbone, the effects of chemical structure upon the oxygen permeation properties of aliphatic-aromatic amorphous polyamides were determined. In this class of polymers, the greatest effects were obtained by alteration of the chain length and disruption of the amide hydrogen bonding by N-alkylation. It is remarkable that reversal of the amide linkage has no effect whatsoever on the permeation properties of the examples studied. 

Shao, Z., Xiong, G., Tong, J. et al. (2001) Ba effect in doped Sr(Coo.8Feo.2)03 g on the phase structure and oxygen permeation properties of the dense ceramic membranes. Separation and Purification Technology, 25,419-429. 

Sunarso, J., Motuzas, J., Liu, S., and Diniz da Costa, J.C. (2010) Bi-doping effects on the structure and oxygen permeation properties of BaSco.iCoo.aOs-s perovskite membranes. /. Membr. Sci., 361,120-125. 

Kawasaki T, Tokuhiro M., Kimizuka N., Kunitake T. Hierarchical self-assembly of chiral complementary hydrogen-bond networks in water. J. Am. Chem. Soc. 2001 123 6792-6800 Kharton V.V., Marques F.M.B. Mixed ionic-electronic conductors effects of ceramic microstructure on transport properties. Curr. Opin. Solid State Mater. Sci. 2002 6(3) 261-269 Kikkinides E.S., Stoitsas K.A., Zaspalis V.T. Correlation of structural and permeation properties in sol-gel-made nanoporous membranes. J. Colloid Interface Sci. 2003 259 322-330 Kilner J., Benson S., Lane J., Waller D. Ceramic ion conducting membranes for oxygen separation. Chem. Ind. November 1997 907-911... 

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