聚丙烯基聚偕氨肟—硫脲络合物引发丙烯腈聚合动力学及机理

MECHANISM FOR THE INITIATION OF ACRYLONITRILE POLYMERIZATION BY POLYPROPYLENE-BASED POLYAMIDOXIME-THIOUREA COMBINATION

研究了硝酸溶液中聚丙烯基聚偕氨肟(PPAO)—硫脲(TU)络合物引发丙烯腈(AN)聚合动力学。在[TU]/[PPAO]<0.5摩尔比的条件下,表观聚合速度(R_p)是R_p=9.1×10~4e^(-45.2k J/RT)[AN]^(2.0)[HNO_3]^(1.5)[TU]^(1.0)聚合物分子量随聚合温度升高而下降,并与硝酸浓度的1.5次方和硫脲浓度的1.0次方成反比,与丙烯腈浓度和 PPAO 浓度无关。可表示为_m=K·1/T·(1/[HNO_3]^(1.5)[TU]^(1.0))=K_M·1/T·(R_p/R_t)根据实验结果,提出了“络合—质子转移”引发机理。

Polymerization of acrylonitriie(AN)in aqueous nitric acid initiated by polypropylene-based polyamidoxime(PPAO)-thiourea(TU)combination has been investigated.The overall rate of polymerization(R_p)under the conditions of[TU]/[PPAO]<0.5 molar ratio is R_p=9.1×10~4e^(-45.2/R)[AN]^(2.0)[HNO_3]^(1.5)[TU]^(1.0) The molecular weights of the polymers were found to be inversely proportional to 3/2-power of nitric acid concentration and l-power of thiourea concentration.In addition,it is independent with the concen trations of monomer and PPAO,and decreases with increasing temperature. On the basis of these experimental results,a coordination-proton transfer mechanism for the initiation was proposed and discussed.