Attempts have been made to synthesize polyphosphazenes with pendent tertiary amino side units via macromolecular substitution. Incorporation of -OCH2CH2N(CH3)(2), -OCH2CH2OCH2CH2N(CH3)(2), and -NHCH2CH2N(CH3)(2) groups was studied. Polymers in which all the side groups consisted of one type of aliphatic tertiary amino-containing unit and species that also contained 2,2,2-trifluoroethoxy or phenoxy groups as cosubstituents were examined. Related phosphazene cyclic trimers were also prepared as small molecule model systems to examine synthetic variables, characterization techniques, and hydrolytic behavior. Those phosphazenes in which the tertiary amino-containing side groups are linked to the skeleton through an aliphatic oxygen-phosphorus bond are sensitive to hydrolysis induced by the basicity of the terminal amino group. However, species in which the tertiary amino-containing units are linked to the backbone through an alkyl nitrogen-phosphorus bond are stable to water and are candidate materials for use in a range of membrane and surface applications. Small molecule model studies also identified reactions of P-Cl bonds in (NPCl2)(3) with N,N-dimethylbutylamine to form dialkylamino-substituted phosphazenes and hydrolysis products.