RESUMO
A new polyacrylate, poly(methylidenelactide), with high thermal stability and derived from biobased resources is reported. This polymer is formed from the radical polymerization of a modified lactide derivative and represents one of the few examples of an acrylic from which the entire mass is bioderived and is made from a simplistic synthesis. Furthermore, poly(methylidenelactide) serves as a foundation for a platform of new acrylic structures, owing to pendant cyclic diesters that are susceptible to postpolymerization modification via simple transesterification chemistry. Several examples of unique acrylics made from poly(methylidenelactide) are synthesized and characterized.
RESUMO
Strong polymer-silica aerogel composites were prepared by chemical vapor deposition of cyanoacrylate monomers onto amine-modified aerogels. Amine-modified silica aerogels were prepared by copolymerizing small amounts of (aminopropyl)triethoxysilane with tetraethoxysilane. After silation of the aminated gels with hexamethyldisilazane, they were dried as aerogels using supercritical carbon dioxide processing. The resulting aerogels had only the amine groups as initiators for the cyanoacrylate polymerizations, resulting in cyanoacrylate macromolecules that were higher in molecular weight than those observed with unmodified silica and that were covalently attached to the silica surface. Starting with aminated silica aerogels that were 0.075 g/cm(3) density, composite aerogels were made with densities up to 0.220 g/cm(3) and up to 31 times stronger (flexural strength) than the precursor aerogel and about 2.3 times stronger than an unmodified silica aerogel of the same density.