Freris I, Cristofori D, Riello P, Benedetti A
Dipartimento di Chimica Fisica, Università Ca' Foscari di Venezia and INSTN, via Torino 155/b, 30170 Venezia-Mestre, Italy.
J Colloid Interface Sci. 2009 Mar 15;331(2):351-5. doi: 10.1016/j.jcis.2008.11.052. Epub 2008 Nov 30.
Polymer encapsulation of submicrometer-sized silica particles by synthesis of the polymer shell, poly(methyl methacrylate) under static conditions in a reaction medium free of surfactants and stabilizing agents is described. The Stöber method, a base-catalyzed hydrolysis and condensation of tetraethyl orthosilicate is used for the synthesis of the monodisperse colloidal dispersion of silica particles. The silica particles are subsequently modified in situ with the surface grafting of the silane coupling agent, 3-(trimethoxysilyl)propyl methacrylate. Encapsulation is achieved using tetraethyl orthosilicate as a reaction medium, in which a thermally initiated radical polymerization of methyl methacrylate is promoted in the presence of the modified particles by a seeding method which leads to a thin coating of poly(methyl methacrylate), and hence silica core-shell particles. The complete encapsulation of individual silica spheres by poly(methyl methacrylate) is visually evidenced by TEM microscopy which reveals the presence of a polymer shell coating up to 10 nm. Evidence for the presence of a poly(methyl methacrylate) shell is further corroborated by DSC/TGA, DRIFT-IR and NMR measurements.
描述了在无表面活性剂和稳定剂的反应介质中，通过聚合物壳聚甲基丙烯酸甲酯的合成，在静态条件下对亚微米级二氧化硅颗粒进行聚合物包封的过程。采用Stöber法，即正硅酸四乙酯的碱催化水解和缩合反应来合成二氧化硅颗粒的单分散胶体分散体。随后，通过硅烷偶联剂甲基丙烯酸3-(三甲氧基硅基)丙酯的表面接枝对二氧化硅颗粒进行原位改性。使用正硅酸四乙酯作为反应介质进行包封，在改性颗粒存在的情况下，通过种子法促进甲基丙烯酸甲酯的热引发自由基聚合，从而形成聚甲基丙烯酸甲酯的薄涂层，进而得到二氧化硅核壳颗粒。透射电子显微镜（TEM）观察直观地证明了聚甲基丙烯酸甲酯对单个二氧化硅球体的完全包封，显示出存在高达10 nm的聚合物壳涂层。差示扫描量热法（DSC）/热重分析法（TGA）、漫反射红外傅里叶变换光谱法（DRIFT-IR）和核磁共振（NMR）测量进一步证实了聚甲基丙烯酸甲酯壳的存在。
