Physico-chemical characterization of nanocapsule polymeric wall using fluorescent benzazole probes

Fluorescent polymers were used to prepare innovative formulations with the objective of verifying the chemical composition of the particle/water interface of nanocapsules at a molecular level. The benzazole dyes distinguish between apolar and polar/protic environments. Comparing the fluorescent behavior of benzoxazole-loaded nanocapsules (entrapped dye) with that of fluorescent-polymeric nanocapsules (chemically bound dye), the results indicated that the latter was exposed to a different environment than that to which the entrapped dye was exposed. The polymer in the nanocapsule suspensions is actually at the oil/water interface, interacting with both inner and outer pseudo-phases at the same time. The polymer is restricted at the particle/water interface forming a wall in nanocapsules. The physico-chemical stability of nanocapsules was studied by fluorescence, light scattering, zeta-potential and potentiometry. After 15, 30, 45 and 60 days of preparation different fluorescent behaviors were observed for the benzimidazole physically entrapped in nanocapsules compared to the benzimidazole chemically bound to the polymer wall. This spectrum presented an isoemissive point indicating that only two species were in equilibrium in the medium. The study showed that the water is increasingly interacting with the polymer in the nanocapsule suspensions. (c) 2007 Elsevier B.V. All rights reserved.