MACROMOLECULAR ENGINEERING OF POLYLACTONES AND POLYLACTIDES .15. POLY(D,L)-LACTIDE MACROMONOMERS AS PRECURSORS OF BIOCOMPATIBLE GRAFT-COPOLYMERS AND BIOERODIBLE GELS

The functional aluminum alkoxide, Et2Al-O-(CH2)2-O-C(O)-C(CH3)=CH2, is a very effective initiator for the (D,L)-lactide (LA) polymerization in toluene at 70-degrees-C. The coordination-insertion type of polymerization is living and exclusively yields linear P (D,L)lactide macromonomers of a predictable molecular weight and a narrow molecular weight distribution. IR and H-1-NMR studies show that the methacryloyl group of the initiator is selectively and quantitatively attached to one chain end, whereas the second extremity is systematically a hydroxyl function resulting from the hydrolysis of the living growing site. alpha,omega-Dimethacryloyl-P(D,L)-lactides, i.e., alpha,omega-macromonomers, have also been successfully synthesized by the additional control of the termination step, i.e., by reaction of Al alkoxide end groups with methacryloyl chloride. Alpha-Macromonomer and alpha,omega-macromonomer P(D,L)-lactides are easily free-radical copolymerized with 2-hydroxyethyl methacrylate (HEMA), resulting in a hydrophilic poly (HEMA) backbone grafted with hydrophobic P(D,L)-lactide subchains and a biodegradable amphiphilic network, respectively. (C) 1994 John Wiley