铈盐引发丙烯腈在含醇羟基硅胶表面的接枝聚合

Graft Polymerization of Acrylonitrile Initiated by Cerium Salt on Surface of Silica Gel Particles

将偶联剂γ-(2,3-环氧丙氧基)丙基三甲氧基硅烷(EPPS)键合于硅胶微粒表面,在酸性催化剂作用下,键合EPPS的环氧键开环,产生了醇羟基(HXYG),形成表面带有醇羟基的改性微粒HXYG-SiO2。使用铈盐与硅胶表面的醇羟基构成氧化还原引发体系,在硅胶表面实施了丙烯腈的接枝聚合,制备了接枝微粒PAN-SiO2,考察了接枝聚合的影响因素。实验结果表明:在所形成的氧化还原引发体系中,由于初级自由基即引发物种处于硅胶微粒表面,所制备的接枝微粒PAN-SiO2具有高的接枝度(0.19 g/g),且单体的整体接枝效率高;引发剂铈盐的浓度对接枝度有较大的影响,铈盐浓度过大,将会促进氧化终止过程,降低接枝度,适宜的铈盐浓度为5.93×10-3mol/L;接枝度随硫酸浓度的增大呈现先增大后减小的变化规律,当H+离子浓度为0.38mol/L时,PAN的接枝度最高。

Coupling agent, 3-glycidoxypropyltrimethoxysilane （EPPS） was bound on the surfaces of silica gel particles. The ring-opening reaction of the epoxy groups of the bound EPPS was performed with acidic catalyst, leading to the modified particles with hydroxy groups HXYG-SiO2 （HXYG）. Graft polymerization of acrylonitrile （AN） was conducted on the particles HXYG-SO2 with the redox initiating system, cerium salt and the hydroxyl groups, to form the grafted particles PAN-SiO2. The effects of factors on the graft polymerization were examined. The experimental results show that the grafted particles PAN-SiO2 have high grafting degree （0.19 g/g） and there is a high graft efficiency of monomer as the initiating species are located on the surfaces of silica gel particles. The concentration of the initiator and cerium salt affects the graft degree of PAN. The excessive cerium salt will accelerate the oxidation termination process, leading to lower graft degree. The eerium salt concentration of choice is around 5.93 × 10^-3 mol/ L. The graft degree of PAN first increases and then decreases with the increasing of sulfonic acid concentration, and it refleets the microscopic mechanism of graft polymerization initiated by cerium salt. As H^＋ concentration is 0.38 mol/L, the graft degree of PAN on PAN-SiO2 microspheres has a maximum value.