光交联Pickering乳液中的粒子稳定剂制备胶体体微胶囊

Preparation of Colloidosome Microcapsules Based on Particle Stabilized Photo-Crosslinkable Pickering Emulsions

研究了光敏性聚合物刷修饰二氧化硅纳米粒子的制备及其乳化行为,提供了一种制备新颖"胶体体"微胶囊的方法.首先,在二氧化硅纳米粒子表面引入原子转移自由基聚合(ATRP)引发剂分子,通过表面引发ATRP得到含有香豆素侧基聚合物刷光敏性的纳米二氧化硅粒子(SiO2-PMMA-PCMA);然后,以该粒子为乳化剂制备油包水型的皮克林乳液;最后,在紫外光的照射下引发香豆素侧基的交联反应从而得到"胶体体"微胶囊.结果表明,香豆素单体7-(2-甲基丙烯酰乙氧基)-4-甲基香豆素(CMA)和SiO2-PMMA-PCMA在紫外光作用下都可以发生交联反应,以SiO2-PMMA-PCMA纳米粒子作乳化剂可以制备稳定的皮克林乳液,光交联后得到的"胶体体"微胶囊的平均粒径约为170μm.

In this work,we studied the preparation and emulsification behavior of nanoparticles with photo-sensitive polymer brushes and presented a method for the preparation of novel colloidosome microcapsules based on single Pickering emulsion template,which is stabilized by surface-modified silica nanoparticles with photodimerizable coumarin group.Firstly,silica nanoparticles were self-made by using a st ber method with a diameter of about 180 nm,following aminated by 3-aminopropyltriethoxysilane（APS） and further modified by 2-bromo-2-methylpropionyl bromide,endowing these nanoparticles with ATRP-initiator reactive group.After that,silica nanoparticles with photo-sensitive polymer brushes（SiO2PMMA-PCMA） were obtained through graft reaction of methyl methacrylate（MMA） and 7-（2-methacryloyloxyethoxy）-4-methylcoumarin（CMA） monomers（with a molar fraction of 4∶1） onto silica nanoparticles by surface-initiated atom transfer radical polymerization（SI-ATRP） method.Here,CMA was synthesized via a two-step method and was detected by UV-visible spectrophotometer.Secondly,the as-prepared hydrophobic SiO2-PMMA-PCMA nanoparticles were dispersed in 2 mL of toluene with a ultrasonic for 5 min（with an interval of 30 s per min）,then 0.5 mL of deionized water was rapidly added,afterwards,water-in-oil type Pickering emulsions were prepared by hand-shake for 3 min.Finally,colloidosome microcapsules were produced through cross-linking reaction of the coumarin group of CMA initiated by UV irradiation,in this step,the SiO2-PMMA-PCMA nanoparticles were locked.The average size and size distribution of as-synthesized Pickering emulsion droplets and colloidosomes were observed with an optical microscope.The results show that both CMA and SiO2-PMMA-PCMA nanoparticles can be initiated to cross-link through the dimerization of the coumarin groups of CMA from different SiO2-PMMA-PCMA nanoparticles via UV irradiation,the dimerization rate of CMA reached about 80% in 6 min and the UV absorption peak of coumarin group of SiO2-PMMA-PCMA nanoparticles was blue-shifted.Besides,the Pickering emulsion droplets can be stored for a long time without breaking up and the average size of as-produced colloidosome microcapsules were about 170 μm.In theory,this method can be scaled up to produce large quantity of colloidosomes.