Synthesis and characterization of biodegradable polylactides and polylactide-block-poly(Z-lysine) copolymers

The reaction of (R,R)-trans-1,2-bis(2,4,6-triisopropylbenzenesulfonamidato)cyclohexane (RRTBSC-H2, 1) with MN[Si(CH3)3] in tetrahydrofuran (THF) produces [(RRTBSC)2M4(THF)4] (2: M = Li, 3: M = Na, 4: M = K). Experimental results show that all three complexes 2–4 are active toward the ring-opening polymerization of l-lactide and compound 2 efficiently catalyzes the polymerization of l-lactide in the presence of a variety of alcohols in a controlled fashion with very narrow polydispersity index. In addition, a variety of biodegradable poly(l-lactide)-block-poly(Nξ-carbobenzyloxy-l-lysine) block copolymers with different ratios have also been synthesized using poly(l-lactide) containing amino chain end (PLLA-NH2) as a macroinitiator.