Preparation of poly[ethylene-g-(vinylbenzyl chloride)] and functionalization with bis(phosphonic acid) derivatives

Poly[ethylene-g-(vinylbenzyl chloride)] (1) film was prepared and used as an intermediate for the synthesis of polymer supported bis(phosphonic acid) derivatives. (1) was synthesized by preirradiation grafting of vinylbenzyl chloride (VBC) on polyethylene film. A reaction time of 29 h gave (1) with a chlorine capacity of 4.7 mmol Cl/g. As shown by energy dispersive X-ray analysis, the depth of the graft modification can be varied from surface to bulk modification by controlling the reaction time. The gel content of the film was found to increase with increased extent of grafting. A 28% VBC grafted film was found to have a gel content of 91%. The swelling of the Poly[ethylene-g-(vinylbenzyl chloride)] (1) film in toluene or THF was rapid A 145% VBC grafted film swells 260 area % within 2 min in refluxing toluene. Tetraisopropyl methylene-bisphosphonate (2) or tetraethyl ethane-1,1-bisphosphonate (3) were reacted with NaH and used for nucleophilic substitution of chlorine in the poly[ethylene-g-(vinylbenzyl chloride)] film. Forty-six percent of the chlorine groups were substituted within 24 h using the sodium salt of tetraisopropyl methylenebisphosphonate (2) in a 10-fold excess in refluxing toluene. Under the same reaction conditions, using the sodium salt of tetraethyl ethane-1,1-bisphosphonate (3) gave 50% substitution. Energy dispersive X-ray analysis showed that the substitution reaction proceeds throughout the film at the same rate, which implies that the reaction is not mass-transfer controlled. Hydrolysis of the polymer supported bisphosphonate in hydrochloric acid to yield the bis(phosphonic acid) form gave a film which swells 60 area % in water at room temperature and 100 area % at 100°C.