Effectiveness of grafting modes of methoxycinnamate sunscreen onto silica particles

Immobilization of p-methoxycinnamate onto silica particles has been performed following two synthesis routes differing by the nature of the coupling agent used for the grafting of UV molecule to silica surface. Different coupling agents, triethoxysilane (TES) in the first route or 3-aminopropyltriethoxysilane (APTS) in the second route, were used. In the first route, the UV molecule was attached to silica by means of a short (C2) or a long (C10) alkyl spacer to study their effect on grafting degree. All synthesis methods led to successful grafting. The grafting degree of UV-filter onto silica particles was two-fold larger in the case of short spacer chains. Better water dispersion was obtained for the material synthesized using the first route. The water dispersion particles remained stable for 40 days. UV-absorbing ability was retained after immobilization of UV-filter molecules onto silica particles in all samples.