Poly［(hexafluoroisopropyloxy)2-x(trifluoroethoxy)x］phosphazene with different substituent ratios was synthesized.The final substituted polyphosphazene products were purified through the THFbenzene precipitation to remove impurity. 31P-NMR was used to assure the purification.The structure of this polymer was characterized by 1H\|NMR

FTIR

XRD

GPC and DSC.Gas permeability coefficients of N2

O2

CH4

CO2

He

H2 in these polymers at 20℃ were measured by the permeate gas pressure method.The trifloroethoxy group showed more competitive substitution than hexafluoroisopropyloxy under same nucleophilic substituted reaction condition.The x-value of three different poly［(hexafluoroisopropyloxy)2-x(trifluoroethoxy)x］phosphazene products were 1.64

1.72 and 1.81 respectively.The glass transition temperature of these polymers were -20.21℃

-42.83℃ and -43.41℃

and the weight\|average molecular weight were 5.07×105

1.49×105and 2.69×105

respectively.These polymers showed higher gas permeability.Its permeability coefficient of N2

CO2 and He were 20 barrer

124 barrer and 85 barrer respectively

and the selectivity coefficient of CO2/CH4 and He/CH4 were 11.5 and 4.8

which showed great potentiality to be applied in natural gas industry.In addition

the selectivity coefficient of H2/N2 was 5.8

the permeability coefficient of H2was 43 barrer

which also showed special potentiality in ammonia synthesis industry.