Synthesis of acetoxyphenyl- and hydroxyphenyl-terminated polyfunctional T8, T_(10), T_(12) silsesquioxanes and initial studies on their use in the formation of highly crosslinked polyesters

摘要

There is continuing interest in the synthesis of polyhydroxy-terminated molecular species for diverse applications ranging from photolithographic materials to intermediates in the synthesis of porous, crosslinked polymers as media for molecular separations, drug delivery etc. We describe here the use of [vinylSiO_(1.5]_8 and [vinylSiO_(1.5)]_(10/12) mixtures to synthesize first-and second-generation acetoxyphenyl compounds via metathesis with p-acetoxystyrene (generation 1, GEN1) or metathesis with p-bromostyrene followed by Heck coupling with p-acetoxystyrene (generation 2, GEN2). The resulting acetoxy compounds were then hydrolyzed to produce octa-, deca- and dodecahydroxy GEN1 and GEN2 compounds. These compounds were purified and then reacted with adipic acid chloride to form the first examples of highly crosslinked polyesters based on silsesquioxanes. The coupling products, their hydrolyzed products and the crosslinked polymers were characterized using a variety of spectroscopic methods. In general, the observed specific surface areas were less than 5 m~2 g~(-1); however, the T8 GEN1 derivative gave a surface area of 25m~2 g~(-1) and was the only crosslinked polymer with a TGA ceramic yield that matched theory for 'perfect' crosslinking. This crosslinked polyester has the shortest organic linker between cages and despite the highly flexible C6 linker provides continuing evidence that it is possible to use the cubic symmetry in these materials to build well-ordered 3-D nanocomposite structures.