超声辐照原位乳液聚合制备P(BA-MMA-AA)/TiO_2纳米复合乳液的研究

通过超声辐照原位乳液聚合制备了稳定的丙烯酸丁酯-甲基丙烯酸甲酯-丙烯酸共聚物P(BA-MMA-AA)/TiO2]纳米复合乳液.系统研究了乳化剂浓度,单体及TiO2用量对超声辐照原位乳液聚合反应的影响.结果表明,随乳化剂浓度增加、单体及TiO2用量的减少,聚合反应速率增高.TEM、SEM和FTIR证实了P(BA-MMA-AA)包覆在纳米TiO2表面,并与TiO2粒子有较强相互作用.用DSC、GPC和1H-NMR表征共聚产物,发现随TiO2加入,共聚物分子量降低,共聚链段中BA单元比例增加,导致聚合物玻璃化转变温度降低.

PREPARATION OF P(BA-MMA-AA)/TiO2 NANOCOMPOSITES THROUGH ULTRASONICALLY INITIATED in situ EMULSION POLYMERIZATION

A new and simplistic method,ultrasonic irradiation technique was employed to prepared(poly(n_butyl) acrylate_co_methyl methacrylate_co_methacrylic acid)P(BA_MMA_AA)]/TiO_2 nanocomposites.By taking advantage of the multiple effect of ultrasound,such as dispersion,pulverization,activation and initiation,the aggregates of TiO_2 particles can be broken down.The polymerization of monomers BA,MMA,and functional monomer AA proceeded while TiO_2 particles were redispersed by ultrasound.The stable P(BA_MMA_AA)/TiO_2 nanocomposite emulsion was obtained.The effects of several main factors,such as surfactant concentration,monomers concentration and the amount of TiO_2,on polymerization rate were investigated.The experimental results showed that with increase in SDS surfactant concentration and decrease in monomers concentration and the amount of TiO_2 the polymerization rate increased.TEM,SEM and FTIR analyses confirmed that polymers were present on TiO_2 surface,and there was strong interaction between TiO_2 and polymers with carboxylic functional groups.DSC,GPC,()~1H-NMR characterizations showed that with the introduction of TiO_2,the average molecular weight of the obtained copolymer decreased,molecular weight distribution became wide,and the BA content of copolymer chains increased compared to that of the pure copolymer,resulting in lower T_g.This method has the following advantages,(1) aqueous medium,(2) without any additional chemical initiator,(3) lower reaction temperature,usually near ambient temperature,(4) ease of operating and(5) the encapsulated polymer layer can be well designed to meet different requirements.