Controlled synthesis and characterization of polyethylene-block-(L,L-lactide)s by combining catalytic ethylene oligomerization with 'Coordination-Insertion' ring-opening polymerization

摘要

Model polyethylene-block-(L,L-lactide) (PE-block-PLA) block copolymers were successfully synthesised by combining metallocene catalyzed ethylene oligomerization with ring-opening polymerization (ROP) of L,L-lactide (LA). Hydroxy terminated polyethylene on rac-dimethyl-silylen-bis(2-methyl-benzeindenyl)-zirconium(IV)-dichloride/methylaluminoxane (rac-MBI/MAO) in presence of diethyl zinc as a chain transfer agent, and subsequent in situ oxidation with synthetic air. Polyethylene-block-(L,L-lactide) block copolymers were obtained via ring-opening in polymerization of LA initiated by PE-OH in toluene at 100 degrees C mediated by tin octoate. The formation of block copolymers was confirmed by H-1 NMR spectroscopy, fractionation experiments, thermal behavior, and morphological characterization using AFM and light microscopy techniques.