聚[2-(2-氯乙氧基)乙氧基)_x(三氟乙氧基)_(2-x)]磷腈合成和气体分离性能研究

六氯环三聚磷腈经二次重结晶一次减压升华纯化后,通过真空热开环聚合和亲核取代反应,用不同摩尔比的2-(2-氯乙氧基)乙醇钠和三氟乙醇纳(1∶3;1∶5;1∶6.5)作为亲核取代试剂混取代聚二氯磷腈,再经多次非溶剂沉淀纯化得到目标聚合物聚(2-(2-氯乙氧基)乙氧基)x(三氟乙氧基)2-x]磷腈.利用31P-NMR监测,以确保得到纯化的聚合物.采用1H-NMR、FT-IR、GPC、DSC、XRD等测试手段对所得到的聚合物进行了结构表征和性能测试,并利用自制的压力法透气性能测定仪测定了这些聚合物的气体渗透系数.结果表明,三氟乙氧基和2-(2-氯乙氧基)乙氧基两种基团已接枝在聚磷腈侧链上,分别得到x值为0.19,0.18和0.08的3种聚(2-(2-氯乙氧基)乙氧基)x(三氟乙氧基)2-x]磷腈,其玻璃化温度分别为-6.37℃,-12.85℃和-25.68℃,重均分子量为5.4×105,6.8×105和1.5×105,在同样的反应条件下,三氟乙氧基较2-(2-氯乙氧基)乙氧基有更强的竞争取代率.这种混取代聚磷腈较单一取代基的聚三氟乙氧基磷腈结晶度小,在本实验中两种取代基比例适中的聚(2-(2-氯乙氧基)乙氧基)0.18(三氟乙氧基)1.82]磷腈的结晶度降至10.1%,这种聚合物显示出较高的气体渗透系数,CO2和He的气体渗透系数达到88.9和60.6 barrer,CO2/CH4和He/CH4的选择系数达到24.1和16.4,在天然气行业显露出良好的应用潜力.此外这类聚合物表现出特殊的H2/N2选择性,选择系数在0.2左右,N2的渗透系数为8.5 barrer,因而在合成氨行业显示出特殊的应用潜力.

SYNTHESIS AND GAS PERMEATION CHARACTERIZATION OF POLY[(2-(2-CHLOROETHOXY) ETHOXY)_x-(TRIFLOROETHOXY)_(2-x)]PHOSPHAZENE

Poly2-(2-chloroethoxy)ethoxy)_x(trifloroethoxy)_(2-x)]phosphazene(PCTFP) was synthesized with thermal ring-opening polymerization and then dual nucleophilic substitution method from hexachlorocyclotriphosphazene(HCCP) that purified by recrystallization twice and sublimation once.The mole ratios of two substituents,which were (2-(2-chloroethoxy)ethoxy) sodium and trifloroethoxy sodium,were 1∶3,1∶5 and 1∶6.5 respectively.The final substituted polyphosphazene products were purified through acetone-benzene precipitation to remove impurity.()~(31)P-NMR was used to assure the purification.()~1H-NMR,FT-IR,GPC,DSC,XRD were used to characterize these PCTFPs,and gas permeability coefficient of different gases of these polymers were measured by the permeate gas pressure method.The results showed that trifloroethoxy and 2-(2-chloroethoxy)ethoxy had been grafted to the side-chain of polyphosphazene,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 5.4×10~5,7.8×10~5 and 1.5×10~5 respectively.Compared with 2-(2-chloroethoxy)ethoxy,trifloroethoxy group showed more competitive substitution under same reaction condition.The degree of crystallinity of these three PCTFPs were lower than that of (poly(bis-trifloroethoxy))phosphazene.In this paper the 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 substituent groups.This polymer showed higher permeability.Its permeability coefficients of CO_2 and He were 88.9 barrer and 60.6 barrer respectively,and the selectivity coefficients of CO_2/CH_4 and He/CH_4 were 24.1 and 16.4,which showed great potentiality to be applied in natural gas industry.In addition,this polymer presented special selectivity of H_2/N_2,which was about 0.2,and the permeation coefficient of N_2 was 8.5 barrer.It also showed special potentiality in ammonia synthesis industry.