No abstract

Acrylate-functionalized copolymers were synthesized by the modification of poly(butyl acrylate-coglycidyl methacrylate) (BA/GMA) and poly(butyl acrylateco-methyl methacrylate-co-glycidyl methacrylate).13 C-NMR analyses showed that no glycidyl methacrylate block longer than three monomer units was formed in the BA/ GMA copolymer if the glycidyl methacrylate concentration was kept below 20 mol %. We chemically modified the copolymers by reacting the epoxy group with acrylic acid to yield polymers with various glass-transition temperatures and functionalities. We studied the crosslinking reactions of these copolymers by differential scanning calorimetry to point out the effect of chain functionality on double-bond reactivity. Films formed from acrylic acrylate copolymer precursors were finally cured under ultraviolet radiation. Network heterogeneities such as pendant chains and highly crosslinked microgel-like regions greatly influenced the network structure and, therefore, its viscoelastic properties.

No abstract

International audiencePrehydrolyzed-condensed precursors containing amino or glycido groups were prepared via sol gel process using various alkoxysilanes in the bulk, without addition of solvent in any step of their preparation. The influence of the experimental set-up, the functionality and ratio of alkoxysilanes, and type of catalyst, on the structure buildup was studied. In the case of amino precursors, the sol-gel process was carried out at weak basic conditions while in the case of glycido precursors the sol-gel process was catalyzed by acid or neutral pH. The sol-gel process was monitored by (29)Si NMR in solution and the structure of the prehydrolysed-condensed precursors was characterized by small-angle X-Ray scattering. The systems with high content of tetraethoxysilane led to the fast gel formation. In weak acid medium tetraethoxysilane formed larger, more condensed species as well as small structures (based on Q (1), Q (2) and Q (3) species) with silanol groups. Strong acidic conditions led to the fast formation of insoluble silica particles in liquid (sol) phase containing monomeric alkoxysilanes. The most suitable precursor formulations based on the alkoxysilanes with amino groups, as well as the most efficient set-up, were selected and used to prepare hybrid organic/inorganic networks based on an epoxy matrix. These networks were characterized using dynamic mechanical analysis