Poly[2-(2-chloroethoxy)ethoxy)x(trifloroethoxy)2-x] phosphaz ene (PCTFP) was synthesized with thermal ring-opening polymerization and then dual nucleophilic substitution method from hexachlorocyclotriphosphazene (HCCP) that purified by recrystallization twice an d sublimation once.The mole ratios of two substituents

which were 2-(2-chloroethoxy)ethoxy sodium and trifloroethoxy sodium

were 1∶3

1∶5 a nd 1∶65 respectivel y.The final substituted polyphosphazene products were purified through acetone-benzene precipitation to remove impurity.31P-NMR was used to as su re the purification.1H-NMR

FT-IR

GPC

DSC

XRD were used to characterize th ese PCTFPs

and gas permeability coefficient of different gases of these polymers were measured by the permeate gas pressure method.The results showed that trifl oroet hoxy and 2-(2-chloroethoxy)ethoxy had been grafted to the side-chain of polyp ho sphazene

and the x-value of these three different (PCTFPs) were 0.19

0.18 and 0.08 respectively.The glass transition temperature of these polymers were -7.37℃，-12.85℃ and -25 .68 ℃

and the weight-average molecular weight were 5.4×105，7.8×105 and 1.5 ×105 res pectively.Compared with 2-(2-chloroethoxy)ethoxy

trifloroethoxy group showed m ore competitive substitution under same reaction condition.The degree of crysta llinity of these three PCTFPs were lower than that of poly(bis-trifloroethoxy)phosphazene.In this paper th e degree of crystallinity of poly［(2-(2-chloroethoxy)ethoxy)0.18(trifloroethoxy)1.82］phosphazene decreased to 10.1% due to its appropriate ratio of the two s ub stituent groups.This polymer showed higher permeability.Its permeability coeff icients of CO2 and He were 88.9 barrer and 60.6 barrer respectively

and the se le ctivity coefficients of CO2/CH4 and He/CH4 were 24.1 and 16.4

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

this polymer pre sen ted special selectivity of H2/N2

which was about 0.2

and the permeation coef ficient of N2 was 8.5 barrer.It also showed special potentiality in ammonia sy nthesis industry.