单一阳离子乳化剂对D4细乳液制备及聚合的影响

Effects of a Single Cationic Emulsifier on Octamethylcyclotetrasiloxane Miniemulsion and Ring-opening Polymerization

无助稳定剂十六醇(HD)时,以十八烷基双聚氧乙烯基苄基氯化铵(OEBA)为单一阳离子乳化剂,制备粒径为200 nm左右的D4细乳液.选OEBA浓度相同、有无HD添加的两对照D4细乳液,经KOH引发进行开环聚合,动态光散射法(DLS)追踪聚合中粒径变化过程.同时借助紫外可见分光光度计,考察合成的聚二甲基硅氧烷(PDMS)细乳液对强酸HCl、强碱KOH和电解质Na Cl的相对稳定性.结果显示,单一乳化剂OEBA时,不但制备的D4细乳液稳定性良好,而且合成的PDMS细乳液具优良的耐强酸、强碱和电解质能力;单一乳化剂时不仅聚合中粒径变化与添加HD相一致,而且反应速率随转化率和时间的变化规律也相似.

As a single cationic emulsifier,octadecyl bis-polyoxyethylene benzyl ammonium chloride（ OEBA）was applied to prepare the stable octamethylcyclotetrasiloxane（ D4） monomer miniemulsion without any costabilizers and non-ionic emulsifiers. The monomer droplet size was about 200 nm after being dispersed through a high pressure homogenizer at 30 MPa for 3 times,the size was similar to that of adding extra hexadecanol（ HD）. The miniemulsion including single emulsifier OEBA（ 0. 0228 mol/L） and the others with extra-adding HD（ 0. 0456 mol / L） were studied as comparative groups. The interfacial shear viscosity（ η） of D4 droplets with different [OEBA] and [HD] was characterized,which was a key parameter of the oil-water interfacial film strength,affecting the stability of monomer miniemulsion. It was discovered that the stability mechanism of monomer miniemulsion with single emulsifier was different from that of conventional miniemulsion. Then D4 miniemulsion was initiated for ring-opening polymerization（ ROP） by KOH solution. During the polymerization processes,change of particle size was traced through the dynamic light scattering（ DLS）. As the polymerization going on,whether using single emulsifier OEBA（ 0. 0228 mol / L） or extra-adding HD（ 0. 0456 mol / L）,the droplet size similarly reduced from 200 nm to 100 nm. Furthermore,the abilities of anti-acid,anti-alkali and anti-electrolyte of polydimethylsiloxane（ PDMS） miniemulsion were defined by E0/ E2 4. It was discovered that stability properties of the miniemulsion with single emulsifier were more excellent than those of the others.Finally,compared with the comparative group including HD,monomer conversion and corresponding polymerization rate at different polymerization stages were determined by gravimetrical method. As expected,the change of polymerization rate with single OEBA was extremely corresponded to the conventional miniemulsion polymerization mechanism. For example,there was no constant rate period in the whole polymerization process.In conclusion,D4 and PDMS miniemulsions could be successfully prepared with only a single emulsifier OEBA.