Fluorescent labels to study thermal transitions in epoxy/silica composites

Abstract

The analysis of the fluorescen response from the dansyl moiety as a function of temperature has been used to estimate the thermal transi-tions in silica particle/epoxy-based composite materials. Silica particles were surface-coated with 3-aminopropyltriethoxysilane (APTES) and 3-aminopropylmethyldiethoxysilane (APDES). 5-Dimethylamino-1-naphtalenesulfonyl chloride (DNS) and 5-dimethylaminonaphthalene-1-(2-aminoehyl)) sulfonamide (DNS-EDA) were selectively attached to the silanized silica particles and to the epoxy matrix respectively. The fluoresce ce results, interpreted in terms of the model of interpenetrating polymer networks, suggest that (i) independent of the silane coating, the interfacial region is slightly more rigid and heterogeneous than the epoxy bulk and (ii) the interface generated with APTES seems to be more flexibl than that obtained with APDES.

The nature of the glass fibre surface and its effect in the water absorption of glass fibre/epoxy composites. The use of fluorescence to obtain information at the interface

“…A small amount of dansyl chloride (DNS-Cl) was dissolved and stirred in 2 mL of a specific silane. The sulfonyl group of DNS-Cl easily reacts with amines [33,35,36] to form the fluorescent sulfonamide derivative (DNSA). The reactant ratio was 1:1000 (dansyl:NH 2 ) ensuring the small amount of fluorophore, required to assume no alteration of the final properties of glass fibre silane coating.…”

“…The advantage of using such a small amount of emissive moieties is that no perturbation is introduced in the system. In general, the fluorescence emission changes when polarity and/or rigidity variations occur in the system where the fluorophore is immersed [33][34][35][36][37][38][39].…”

Detection in a single experiment of thermal transitions of the constituents in PS/BaTiO3 composites

“…One way to analyze the contribution at longer wavelengths when there are BaTiO 3 particles within the PS is to use the so called first moment of the emission band, on 4, [1][2][3][4]7,8,10] which represents the average energy of the light emitted:…”

“…Several studies about polymeric systems have revealed a sharp change in the tendency of the fluorescence intensity of fluorescent probes at a certain temperature [3,10]. These phenomena can be understood by considering the following equation where quenching phenomena and chemical reactions are considered negligible:…”

“…The fluorescence emission coming from many molecules or groups (fluorophores) is so sensitive to changes in its immediate surroundings that very small amount of them are enough to obtain information at nanoscale of the materials where they are immersed [1][2][3][4][5][6][7][8]. Intrinsic fluorescence of polystyrene has been successfully used to study thermal transitions and other phenomena in composites and blends [6,9].…”