Synthesis of terpyridine-containing polycarbonates with post polymerization providing water-soluble and micellar polymers and their metal complexes

Abstract

Carbon dioxide based polymers synthesized from the metal-catalyzed copolymeriation of epoxides and CO₂ containing the terpyridine ligand as an end group are reported. The strategy used was to carry out the polymerization in the presence of a carboxylic acid derivative of terpyridine, 4′-(4-carboxyphenyl)-2,2′:6′,2′′-terpyridine (HL), as a chain transfer agent. The epoxide monomer possessing a vinyl substituent, allyl glycidyl ether (AGE), was copolymerized with CO₂ employing a (salen)Co(III) catalyst to afford a polycarbonate which upon the addition of mercaptoacetic acid across the double bond, followed by deprotonation, yielded a water soluble polymer. In a similar manner, the sequential formation of a diblock terpolymer produced from propylene oxide, AGE, and CO₂ provided a amphiphilic polycarbonate which self-assembled upon addition to water to form micelle nanostructures. The molecular weights of these CO₂-derived polycarbonates were shown to be easily controlled by the quantity of chain transfer agent used. These polymeric ligands were demonstrated to provide a modular design for synthesizing a wide variety of metal complexes as illustrated herein for zinc and platinum derivatives.