Chemical manipulation of polyhedral oligomeric silsesquioxanes for the synthesis of modular materials and catalysts

Abstract

A study has been undertaken to investigate the chemical modification of near cubic polyhedral oligomeric silsesquioxanes (POSS) of the general formula [RSi03/2]8 to produce molecular building blocks suitable for the preparation of microporous modular solids with engineered properties. Several approaches have been taken in an effort to prepare octa-fiinctional POSS suitable for self-assembly resulting in the synthesis of new benzoic acid functionalised POSS and, preliminary analysis suggests, two new highly functionalised pyridine bearing POSS. Studies into the use of Heck type arylation, the Gabriel synthesis and thyl radical reactions to modify functionalised POSS have also been undertaken with a view to identifying new synthetic routes to functionalised POSS. During efforts to investigate the requirements for the preparation of porous materials from POSS, several new copolymers were prepared through hydrosilylation of POSS only and POSS-spacer mixtures. Three of these copolymers are porous in nature and have high surface areas measuring several hundred meters square per gram. Acid cleavage has been used to alter the form of one of these copolymers by, it is suggested, opening individual POSS within the structure of the material. This demonstrates that it is possible to modify linked POSS molecules in a manner and may provide a route to catalytic materials from POSS copolymers and, potentially, extended networks of POSS.