ACIDIC PROPERTIES OF FUNCTIONALIZED SILICA-SUPPORTED POLYMERS - RELATION BETWEEN REACTIVITY AND MORPHOLOGY

To improve and extend the properties of organic polymer-supported cata lysts, the corresponding functional polymers were grafted on porous si lica. Mechanical stability and constant shape, which are independent o f solvent nature, and the possibility of modulating polarity to fit th at of the reagents are new advantages. After a study of the grafting m echanism to understand the extent of grafting and chain length control , we tried to determine the optimal catalyst structure. Styrene was po lymerized in the presence of a trifunctional silanoxy chain transfer a gent in various amounts and was reacted with silica and then sulfonate d. The acid catalytic properties of the resulting materials were evalu ated in three tests of interest and were compared to those of referenc e materials. Selectivity was excellent. Reactivity was dependent upon catalyst compatibility with the reagents and the presence of water, wh ich alters stability. Reactivity was poor for toluene alkylation, mode rate for t-butanol dehydration, and good for ketalization. The specifi c activity was higher for a high number of short chains than for a low number of long chains at a given polymer to silica ratio. (C) 1997 Jo hn Wiley & Sons, Inc.