We describe herein the synthesis and controlled ring-opening metathesis polymerization (ROMP) of highly functional zwitterionic sulfopropylbetaine- and carboxyethylbetaine- exo -7-oxanorbornene derivatives with the first-generation Grubbs' initiator RuCl 2 (PCy 3 ) 2 CHPh in a 2,2,2-trifluoroethanol/methylene chloride solvent mixture. These are the first examples of such norbornene-based betaine substrates. Both species can be polymerized directly in a controlled manner in organic media as judged from the kinetic profiles and aqueous size exclusion chromatographic analysis. This represents the first time betaine monomers have been polymerized directly in a controlled fashion by a technique other than a controlled free radical polymerization process, and the first time it has been achieved in organic, as opposed to aqueous, media. Finally, preliminary results demonstrate that water-soluble, salt-responsive AB diblock copolymers can be prepared and that such materials are able to undergo supramolecular self-assembly in aqueous media to yield nanosized aggregates simply by controlling the aqueous electrolyte concentration.
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Rankin et al. (2007) studied this question.