CHEMICAL MODIFICATION OF MONOLITHIC POLY(STYRENE-DIVINYLBENZENE) POLYHIPE(R) MATERIALS

Monolithic samples of highly porous poly(styrene/DVB) PolyHIPE(R) have undergone a number of electrophilic aromatic substitution reactions, namely sulfonation, nitration and bromination. Mild, hydrophobic reage nts and homogeneous reaction conditions were sought in an effort to ac hieve uniform chemical modification, to a reasonable degree of substit ution, throughout the large polymeric structures. Thus, sulfonation wa s Carried out with lauroyl sulfate in cyclohexane, nitration with tetr abutylammonium nitrate-trifluoroacetic anhydride (TBAN-TFAA) in dichlo romethane and bromination with bromine-stannic chloride in dichloromet hane. An average degree of sulfonation of 2.4 mmol g(-1) was achieved, with a drop in sulfonic acid content of approximately 1 mmol g(-1) fr om surface to centre. Nitration occurred to a lesser extent, with simi lar differences in substitution between surface and centre being obser ved. PolyHIPE(R) monolithic samples were brominated to an extent of 3. 6 mmol g(-1) furthermore, this was uniform across the entire substrate . The differences in extent of each reaction are explained by consider ation of such factors as the nature of the solvent, polarity of the re agents and compatibility between the reagents and the polymer matrix t hroughout the reactions.