Hyperbranched poly(ε-caprolactone)s

Novel hyperbranched poly(ε-caprolactone)s have been synthesized. The versatile synthesis utilizes AB2 macromonomers and allows the thermo-physical properties of the polymers to be tailored. The ε-caprolactone-based AB2 macromonomers were synthesized through living ring opening polymerization, using aluminum benzyloxide as the initiator. The aluminum benzyloxide initiated polymers were then functionalized with benzylidene-protected 2,2′-bis(hydroxymethyl) propionic acid and subsequently deprotected to form the α-carboxylic-ω-dihydroxy functional AB2 macromonomers. The AB2 polyesters were condensed into hyperbranched polymers through a room-temperature esterification synthesis using dicyclohexylcarbodiimide (DCC) and 4-(dimethylamino)pyridinium 4-toluenesulfonate (DPTS). All polymers were characterized by 1H NMR, SEC, and DSC. The degree of branching in the hyperbranched polymers was found, by 1H NMR, to be 0.37 ± 0.03, and to be independent of the macromonomer used. Significant flexibility exists in the new approach since the molecular weight and the type of macromonomer can be varied.