摘要:
The invention relates to a process for the preparation of monolithic xerogels and aerogels of silica/latex hybrids under subcritical conditions. In the two-stage synthesis of these alcogels in the presence of an acid-base catalyst, the hydrolysis and polycondensation of a silicon alkoxide are carried out in an organic medium containing excess water. A latex consisting of polybutyl methacrylate and polybutyl acrylate, modified with alkoxysilane groups, is first synthesized and then incorporated in the mixture either in the first stage in order to effect its co-hydrolysis with the silicon alkoxide, or in the second stage to effect its co-condensation with the previously hydrolysed colloidal silica. The resulting alcogels are aged, washed, and dried under subcritical conditions. This process gives hybrid products containing 0.1-50 wt-% of latex and having a density of 300-1300 kg/m3, a porosity of 40-85%, a specific surface area of 400-900 m2/g and a mean pore diameter of 2-12 nm. The products are resistant to atmospheric humidity and moisture, have better mechanical properties than the corresponding inorganic products, and can be used as thermal, acoustic and electrical insulators.
摘要:
The invention relates to fluorescent polymers soluble in an aqueous solution carrying at least 5 fluorophores which are distributed on the polymer and which exhibit the following properties: the fluorophores are water-soluble, the fluorophores are not self-associated in water at a concentration of less than or equal to 10−4 mol/l, preferably at a concentration of less than or equal to 10−3 mol/l, the fluorophores which are free in the aqueous solution have a molar extinction coefficient of greater than 1000 M−1·cm−1, preferably greater than 5000 M−1·cm−1, the fluorophores which are free in the aqueous solution have a quantum yield of greater than 0.3, preferably greater than 0.6, said polymers having a fluorescence amplification factor of greater than or equal to 0.35 per kg/mol of polymer, preferably greater than 0.45 per kg/mol of polymer.