A series of alkyl- and fluoroalkyl-substituted polyphosphazenes, {[Me(Ph)PN](x)[(RMe(2)SiCH(2))-(Ph)PN](y)}, were prepared by deprotonation of the methyl groups on [Me(Ph)PN](n) with n-BuLi, followed by treatment of the intermediate anion with the corresponding chlorosilanes, RMe(2)SiCl [where R = (CH)(2)CH3, (CH2)(3)CH3, (CH2)(7)CH3, (CH2)(9)CH3, (CH2)(17)CH3, (CH2)(2)CF3, (CH2)2(CF2)(5)CF3, and (CH2)2(CF2)(7)-CF3]. The new polymers were characterized by elemental analysis, gel permeation chromatography, and H-1 and P-31 NMR spectroscopy. The range of substitution [i.e., y/(x + y) x 100%] was between 40 and 70% as determined by elemental analysis. The glass transition temperatures, which were determined; by differential scanning calorimetry, decreased as the length of the side chain increased and ranged from -20 to +39 degrees C. Onsets of decomposition, which were measured in air using TGA, were between 290 and 350 degrees C. Contact angle measurements made with water showed that the new polymers became more hydrophobic as the length of the alkyl side group increased and values ranged from 90 to 97 degrees. Those polymers with fluoroalkyl side groups were less wettable with contact angles between 97 and 101 degrees. Ah these values were Significantly larger than the contact angle of 73 degrees for the parent polymer.