Steady state fluorescence to study nanocomposites based on silica nanoparticles and thermoplastic polymer matrices

Abstract

Steady state fluorescence was used to study the interfaces of composites formed by silica nanoparticles and three polymers: poly(methylmethacrylate) (PMMA), polystyrene (PS), and low density polyethylene (LDPE). The fluorescent response from the pyrene-1-sulfonamide (PSA) was used to study changes appearing in its immediate surroundings. Molecular dynamics of the polymers was studied monitoring the fluorescent response from the PSA as a function of temperature. When the fluorophore was dispersed within the polymers, information from their bulk was obtained while, attaching the fluorophore to the surface of the silica nanoparticles, information from the interface was collected. In the case of the amorphous polymer matrices (PMMA and PS), the presence of silica nanoparticles exerts a small constrain effect by reducing the chain mobility. In the case of the semicrystalline thermoplastic polymer (LDPE) when nanoparticles are not present, only one clear relaxation assigned to the typical diffusion-like motion of chain segments in the crystallites has been observed. However, when nanoparticles are within the polymer, three relaxations are clearly observed: one in the interlamellar amorphous phase and two due to diffusion-like motion of chain segments in the crystallites under or without the influence of the nanoparticles, respectively. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers