New well-defined polymeric betaines: First report detailing the synthesis and ROMP of salt-responsive sulfopropylbetaine- and carboxyethylbetaine-exo-7- oxanorbornene monomers

Abstract

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) 2CHPh 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. © 2008 American Chemical Society.