杂质对六氯环三聚磷腈热聚合的影响

利用红外光谱、磷核磁共振谱、广角X射线衍射、差示扫描量热、凝胶色谱等分析手段,研究了六氯环三聚磷腈(HCCP)在存放过程中产生的杂质,以及不同纯化方法对这些杂质的去除效果,探讨了这些杂质对HCCP单体真空热开环聚合反应的影响.HCCP在存放过程中接触空气中的水汽在环上氯基团处易被水解,产生Trimer-1、Gem-2、Dimmer-3等杂质,重结晶能去除Gem-2、Dimmer-3和少量的Trimer-1,升华能较好地去除Trimer-1.杂质Gem-2、Dimmer-3中的羟基引发聚二氯磷腈交联,生成不可溶的交联态聚二氯磷腈,而Trimer-1则会降低聚合速度,并在聚合物中引入磷氧基和亚胺基杂链,从而影响后续聚磷腈取代产物的性质,表现为聚合物中晶态发生变异,结晶度降低,玻璃化温度、晶态转化温度和熔融温度出现差别.用重结晶结合升华的方法对HCCP单体进行纯化后,应用FTIR或31P-NMR分析来验证纯化效果,以确保能控制聚合速度和时间,使聚合顺利进行.

EFFECTS OF IMPURITIES ON THE THERMAL VACUUM POLYMERIZATION OF HEXACHLOROCYCLOTRIPHOSPHAZENE

The effect of hydrolysis derivatives of hexachlorocyclotriphosphazene(HCCP) on its thermal vacuum polymerization was investigated.FTIR and()~(31)P-NMR spectra were used to analyze the impurities in HCCP.The impurity removing effectiveness of different purification methods and the influence of residual impurities on thermal vacuum ring-open polymerization reaction of HCCP were studied.Poly(bistrifloroethoxy)phosphazene(PTFEP) was synthesized according Allock's method by using HCCP which was purified with different methods.FTIR,()~(31)P-NMR,WAXR,DSC and GPC were used to analyze the characteristic properties of PTFEP.The results showed that HCCP with chloro-attached rings could be hydrolyzed by water vapor in the atmosphere and generated impurities such as Trimer-1,Gem-2,Dimmer-3,et al.Recrystallization can remove Gem-2,Dimmer-3 and some Trimer-1.There were still some Trimer-1 remaining in HCCP purified only by recrystallization.Sublimation can remove trimer-1 well.In the process of thermal vacuum ring-open polymerization of unpurified HCCP(250℃,10 Pa),with unpurified monomers,which contained impurities of Trimer-1,Gem-2 and Dimmer-3,the soluble polydichlorophosphazene(PDCP) could be got only when the polymerization time was within range of 8 h and the monomer conversion was(6.8%.)When the polymerization time exceeded 10 h crosslinking polymer appeared.When HCCP purified by twice recrystallization or by one recrystallization plus one sublimation was used as polymerization monomer,the conversion of the former were 21.4%(64 h) and 32.6%(78 h),that of the latter were 60.0%(64 h) and 70.6%(78 h),and no crosslinking polymer appeared.For the polymer PTFEP made from HCCP purified by recrystallization or by recrystallization plus sublimation,its crystalline state,crystallinity,glass temperature,crystalline state conversion temperature and the melting temperature also changed.The FTIR spectra showed that there were phosphinyl(1621 cm~(-1)) and imino(2971 cm~(-1)) groups existed in PTFEP systhesized with HCCP purified only by recrystallization.It was considered that the hydroxy groups in Gem-2 and Dimmer3 resulted in crosslinking of PDCP and unsoluble polymerization.The inpurity of Trimer-1 reduced the polymerization rate,brought in the phosphinyl and imino groups in the polymer and then influences its characteristic properties.It's the reason that the yield of soluble polydichlorophosphazen produced from HCCP purified just by recrystallization was smaller than that from HCCP purified by recrystallization and sublimation.FTIR or()~(31)P-NMR analysis were advised to validate the purified effect of HCCP and assure the polymerization.