Effect of functionalization on the properties of silsesquioxane: a comparison to silica

While similar in nature, the properties of silica and silsesquioxane are very different, but little is known about these differences. In this paper, functionalized silsesquioxane microparticles are synthesized by adapting the modified Stober method and post-functionalized with rhodamine B. The as-synthesized silsesquioxane particles are characterized by a variety of physical and chemical methods. The synthesized particles are amorphous and nonporous in nature and are less dense than silica. While silsesquioxane and silica have some similar physical properties from their siloxane core, the organic functional group of silsesquioxane and the one-half oxygen difference in its structure impact many other properties of these particles like their charging behavior in liquids. These differences not only allow for the ease of surface modification as compared to that necessary to modify silica but also allow for the use in a variety of colloidal systems that due to pH or electrolyte concentrations may not be suitable for silica particles.