ORIGINAL CONTRIBUTION Monitoring the formation of polystyrene/silica nanocomposites from vinyl triethoxysilane containing copolymers Juan F. Lopez & Gabriel J. Pelaez & Leon D. Perez Received: 4 June 2012 / Accepted: 28 October 2012 / Published online: 14 November 2012 # Springer-Verlag Berlin Heidelberg 2012 Abstract Random copolymers of polystyrene-co-polyvinyl triethoxysilane (PS-co-PVTES) were prepared via semi-batch emulsion polymerization with different feed monomer compo- sitions and evaluated as precursors of polystyrene (PS)/silica nanocomposites. Small-angle X-ray scattering (SAXS) profiles acquired from 20 °C to 180 °C showed that, at temperatures higher than glass transition temperature (T g ) of PS, the latex particles aggregate. On thermal annealing at 180 °C, silica-rich domains are formed, as corroborated by scanning electron mi- croscopy. Infrared spectroscopy and differential scanning calo- rimetry analyses showed a reduction of the silanol concentration and an increase in the T g value, respectively. The silica long domain spacing, measured by SAXS, depends on the concen- tration of vinyl triethoxysilane (VTES) in the feed; this value varied from 35 to 57 nm when the weight ratio of the monomers (styrene/VTES) was 50:50 and 90:10, respectively. Keywords Vinyl triethoxysilane . Emulsion polymerization . Organic-inorganic copolymers . Nanocomposites . SAXS Introduction Polymer-based nanocomposites are a new kind of advanced materials to which high academic and industrial interest have been devoted, because they can combine beneficial properties of the polymers such as flexibility, ductility, pro- cessability, and other functionalities, with the rigidity and thermal and mechanical stability which are characteristic of mineral fillers. The extent of property enhancement is strongly dependent on the size of the mineral particles into the polymer matrix. For instance, increase of the mechanical and dynamical properties of composite materials is favored when the interfacial area increases. The expectation of hav- ing their particles and aggregates in the nanoscale range as fillers have encouraged the use of novel nanomaterials, which include single-wall and multiwall carbon nanotubes, exfoliat- ed clays, graphite sheets or nanoplatelets, silica nanoparticles, and polyhedral oligomeric silsesquioxanes [1–6]. Although very fine particles can be synthesized, filler-matrix interac- tions are crucial to improve the filler dispersion, as well as the adhesion of the polymer matrix to the filler surface, which in turn increases the effective filler volume and allows synergis- tic interactions between the components. Silica fillers have been widely explored, due to several factors; their cost is relatively low compared with other materials, and silica particles can also be synthesized in a broad range of particle sizes and shapes [7]. Although the dispersion of silica into most of the polymer matrices is challenging due to the presence of highly polar silanol groups, the design of polymer/silica composites constitutes a growing research topic in the field of materials science; numerous polymer matrices and preparation methods have been reported [8, 9]. The dispersion of silica filler into polymers can be im- proved through several strategies, which include controlling the processing parameters [10, 11], the use of additives [12, 13], and the modification of the particles surface to either reduce their polarity or sterically avoid their aggregation [5]. Nevertheless, in several cases, those strategies do not conduct to significantly enhance the adhesion forces between polymer J. F. Lopez : G. J. Pelaez Grupo Ciencia de los Materiales, Instituto de Química, Universidad de Antioquia, Medellin, Colombia J. F. Lopez e-mail: jfgiraldo@exactas.udea.edu.co L. D. Perez (*) Departamento de Química, Pontificia Universidad Javeriana, Bogota, D.C., Colombia e-mail: leon.perez@javeriana.edu.co Colloid Polym Sci (2013) 291:1143–1153 DOI 10.1007/s00396-012-2842-4