Synthesis and characterisation of porous polymers

Abstract

Highly porous silsesquioxane based copolymers, deriving from vinyl and hydridosilsesquioxane monomers, have been synthesised. These materials have been characterised in order to determine their chemical structure, with particular emphasis upon the surface area and porosity. A number of slight variations to the composition has also been considered, showing similar physical properties to those prepared earlier. In most cases the materials produced are observed to be highly porous, with surface areas typically around 500m²/g. Additionally the thermal behaviour was investigated, with the copolymers seen to start breaking down at temperatures over 150°C. Subsequently these silsesquioxane copolymers have been used as supports for a number of different transition metal species. This was achieved by means of opening the silsesquioxane ring structure in the presence of a base, before insertion of chlorine containing complexes of titanium, zirconium, molybdenum or cobalt. The porosity of these was comparable to results prior to the insertion, with only a slight reduction in surface area. The preparation of copolymers containing zirconium and cobalt species was also attempted by preparing monomeric silsesquioxanes possessing these metals, and then conducting the polymerisation. From this a zirconium containing porous polymer was successfully prepared. Extended x-ray absorption fine structure (EXAFS) was used to determine the structure of the metal containing species, and results compared with samples with the metal species having been inserted in monomelic species. From this data a number of likely structures for these materials was proposed.