GAS PERMEATION STUDIES OF SILYLATED DERIVATIVES OF POLY(METHYLPHENYLPHOSPHAZENE)

Several silylated derivatives of poly(methylphenylphosphazene) [Me(Ph) PN](x)[RMe(2)SiCH(2)-(Ph)PN](y) [R = CH3, 3; (CH2)(2)CH3, 4; (CH2)(2)C F3, 5; and (CH2)(2)(CF2)(8)F, 6] were prepared via deprotonation of th e methyl group of [Ph(Me)PN](n) with n-BuLi followed by the treatment with chlorosilanes. Three new terpolymers, (x)[Me(3)SiCH(2)(Ph)PN](y)[ RMe(2)SiCH(2)(Ph)PN](z) [R = (CH2)(2)(CF2)(8)F; x = 0.44, y = 0.14, z = 0.42, 7; x = 0.46, y = 0.27, z = 0.27, 8; x = 0.33, y = 0.54, z = 0. 13, 9], were also prepared via cosubstitution using varying ratios of Me(3)SiCl and RMe(2)SiCl. Structural characterization and purity of ea ch of these polymers were established by H-1 and P-31 NMR spectroscopy , elemental analysis, and differential scanning calorimetry. The gas p ermeabilities of membranes of these polymers were determined at 35 deg rees C and compared to that of the parent polymer [Me(Ph)PN](n), 1, fo r which permeabilities to N-2, O-2, CH4, and CO2 were 0.6 x 10(-10), 1 .8 x 10(-10), 0.7 x 10(-10), and 6.5 x 10(-10) cm(3)(STP). cm(-1). cmH g(-1). s(-1), respectively. The incorporation of the silyl groups gene rally increased permeabilities relative to [Me(Ph)PN](n) without signi ficant changes in selectivity. Polymers from the cosubstitution reacti ons had as much as a 15-fold increase in gas permeabilities with selec tivity ratios (e.g., alpha(CO2/CH4) = 8.9) similar to those of 1. The trimethylsilyl groups also increased the T-g values of the terpolymers 7-9 relative to the simple derivative 6. The gas permeation propertie s of these polymers are discussed with respect to the lengths and conc entration of the side groups.