Relationships between refractive index change and light scattering during photopolymerization of acrylic composite formulations

Light scattering by filler particles is the main cause of the decrease in light intensity inside a photocurable composite material. This scattering phenomenon depends on the matrix and filler refractive index gap. This work aims to elaborate a non scattering photocured composite by minimizing this gap. Relationships between refractive index and conversion of unloaded acrylic formulations were first studied by real time infrared spectroscopy and refractometry. Refractive index of the final polymer was especially related to its monomers composition. These results allowed matching the matrix and silica refractive indexes, i.e., determining the suitable composite formulation which led to a non scattering material.