Molecular Dynamics Simulation of Hydrogels Based on Phosphorylcholine-Containing Copolymers for Soft Contact Lens Applications

The structure and dynamics of copolymers of 2-hydroxyethyl methacrylate (HEMA) with 2-methacryloyloxyethyl phosphorylcholine (MPC) were studied by molecular dynamics simulations. In total, 20 systems were analyzed. They differed in numerical fractions of the MPC in the copolymer chain, equal to 0.26 and 0.74, in the sequence of mers, block and random, and the water content, from 0 to 60% by mass. HEMA side chains proved relatively rigid and stable in all considered configurations. MPC side chains, in contrast, were mobile and flexible. Water substantially influenced their dynamics. The copolymer swelling caused by water resulted in diffusion channels, pronounced in highly hydrated systems. Water in the hydrates existed in two states: those that bond to the polymer chain and the free one; the latter was similar to bulk water but with a lower self-diffusion coefficient. The results proved that molecular dynamics simulations could facilitate the preliminary selection of the polymer materials for specific purposes before their synthesis

Interface effects on the NLO properties of guest-host materials

International audienc

Some fundamental and applicative properties of [polymer/nano-SiC] hybrid nanocomposites

International audienceHybrid nanocomposites which combine polymer as host matrix and nanocrystals as active elements are promising functional materials for electronics, optics or photonics. In these systems, the physical response is governed by the nanocrystal features (size, surface and defect states), the polymer properties and the polymer-nanocrystal interface. This work reviews some selective nanostructured architectures based on active elements such as silicon carbide (SiC) nanocrystals and polymer host matrices. Beyond an overview of some key properties of the nanocrystals, a main part will be devoted to the electro-optical (EO) properties of SiC based hybrid systems where SiC nanocrystals are embedded in polymer matrices of different chemical nature such as poly-(methylmethacrylate) (PMMA), poly-vinylcarbazole (PVK) or polycarbonate. Using this approach, the organic-inorganic interface effects are emphasised with regard to the dielectric or hole transporting behaviour of PMMA and PVK respectively. These effects are illustrated through different EO responses associated with hybrid composites based on PMMA or PVK

Cluster approach to the electronic properties modeling of TiO2 nanocrystals sensitized by doping agents and dye molecules

International audienc

Electrooptic effect in hybrid polymer-SiC nanocrystals

International audienc

Electro-Optical Effects in SiC Nanocrystals Incorporated in Polymer Matrices

International audienc

Effets Electro-optiques dans les films minces hybrides (Polymère-SiC nanocristaux)

National audienc

Photoluminescence features on the Raman spectra of quasistoichiometric SiC nanoparticles: Experimental and numerical simulations

International audienceVisible photoluminescence (PL) broad bands are observed in the Raman spectra of SiC nanoparticles (np-SiC) with diameters ranging from 10 to 25 nm. The phenomenon is studied versus the particle size, chemical composition, annealing, and oxidation treatments. In the case of quasistoichiometric np-SiC, excitation by 514-nm radiation gives rise to broad red PL emissions mainly enhanced by the amorphous fraction of the particles and by the surface chemical disorder induced by oxidation. The PL spectra are quantitatively analyzed using numerical methods based on cluster approaches. PL bands are calculated as a function of the cluster geometry and defects (carbon and silicon vacancies), as well as the oxygen location within np-SiC sites. The relevance of this numerical analysis is discussed to account for the main features of the PL broad structure. The PL signature in SiC nanopowders can be used to monitor the physical organization of the np-SiC and to point out their amorphous structure fraction, surface states, and the defect contents

Linear electro-optical effects in the Hybrid Matrices polymer/SiC Nanocrystals

International audienc