###### Abstract  
Polymer microspheres are important for a variety of applications, such as ion exchange chromatography, catalyst supports, absorbents, etc. Synthesis of large microspheres can be challenging, because they cannot be obtained easily via classic emulsion polymerization, but rather by more complex methods. Here, we present a facile method for obtaining polymer microspheres, beyond 50 \(\upmu\)m, via Pickering emulsion polymerization. The method consists in creating oil-in-water (\(o/w\)) Pickering emulsion/suspension from vinyl bearing monomers, immiscible with water, whereas silica nanoparticles (NPs), bearing glycidylI functionalities, have a stabilizing role by adsorbing at the monomer/water interface of emulsion droplets. The emulsion is polymerized under UV light, and polymer microspheres decorated with NPs are obtained. We discovered that the contact angle of the NPs with the polymer microsphere is the key parameter for tuning the size and the quality of the obtained microspheres. The contact angle depends on the NPs' interfacial energy and its polar and dispersive contributions, which we determine with a newly developed NanoTraPPED method. By varying the NPs' surface functionality, we demonstrate that when their interfacial energy with water decreases, their energy of adhesion to water increases, causing the curvature of the polymer/water interface to decrease, resulting in increasingly larger polymer microspheres. p pacs: 21.30.Hc, 11.30.-d, 12.60.-c, 11.30.Jc, 12.60.-c, 12.  
as diffusion, interaction, 2D assembly of particles at liquid-liquid interfaces [23; 24; 25; 26], etc. The application potential of Pickering emulsions technology in manufacturing nano and microstructures can be greatly expanded by combining it with complementary methods; for example, micron sized hollow spheres decorated with catalyst nanoparticles could be obtained [27] from combining Pickering emulsification with non-solvent induced phase separation (NIPS) method. NIPS is a widely used method for fabrication of polymeric membranes and microspheres [28; 29; 30]. Another particularly attractive aspect related to Pickering emulsions is the possibility to polymerize them, when the oil phase is a water immiscible vinyl bearing monomer; this way a plethora of new polymeric nano- and micromaterials can be obtained, including molecular imprinted polymers [6; 22; 31], colloidal particles with structural complexity [32], conductive nanostructured microcapsules [33], organic-inorganic composite particles [34], etc. In a recent report, we have shown that the Pickering emulsion polymerization technology can be used to measure the surface energy and surface energy components of the emulsion stabilizing particles [35]. How are the Pickering emulsions stabilized by particles? In essence, the problem has been already addressed since 1923, at least at the conceptual level [36], when [PERSON] et al. [37] suggested that the particles used as stabilizer of emulsions have to be wetted to some degree by both phases, the oil and water, in order to adsorb at the oil-water interface. Furthermore, the difference in wettability \"bends\" the interface in the direction of more poorly wetting liquid, thus causing its emulsification and breaking into droplets. Thus, if it were possible to measure the wettability of particles by water and oil, one can predict the type of emulsion generated \(o/w\) or \(w/o\) based on the difference in wettability. In 2001, [PERSON] and [PERSON] [38], and in a later work by [PERSON] [39], tried to predict the Pickering emulsion phases from the relative interaction strength of the NP-oil and NP-water as reflected in the magnitude of interfacial energies between the three phases of an emulsion. They have calculated the contact angle of a theoretical NP with various oils and water, starting with literature data of the surface energy and its polar and disperse components.