The mixed substituent cyclophosphazene monomers N3P3Cl4(OCHCH2)(OCH2CF3) (2) and N3P3Cl3(OCHCH2) (OCH2CF3)2 (3) undergo polymerization under radical initiation conditions to yield the mixed substituent poly[(vinyloxy)cyclotriphosphazenes] [CH2CH(ON3P3Cl4(OCH2CF3))]n(5) and [CH2CH(ON3P3Cl3(OCH2CF3)2)]n (6), respectively. A significant, progressive reduction in molecular weight compared to the parent polymer of the series [CH2CH(ON3P3Cl5)]n (4) was observed and attributed to increased chain transfer. The thermal decomposition of 5 and 6 is similar to that observed for 4 with an exothermic elimination of HCl at modest temperatures. An alternative synthetic pathway involving nucleophilic substitution reactions of 4 provided [CH2CH(ON3P3(OCH2CF3)5)]n (7), [CH2CH(N3P3Cl2(OC6H5)3)]n (8A), [CH2CH(ON3P3Cl1.7(OC6H5)3.3)]n (8B), [CH2CH(ON3P3Cl1.5(NHCH3)3.5)]n (9), [CH2CH(ON3P3Cl3.8 (N(CH2CH3)2)1.2]n (10A), [CH2CH(ON3P3Cl3.4(N(CH2CH3)2)1.6)]n (10B), and [N3P3Cl2(OCHCH2)(N(CH3)2)]n, (11). The thermal behaviors of all of the new polymers were examined by TGA, DTA, DSC, and pyrolysis mass spectrometry. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2288-2293