Synthesis and Characterization of Block Copolymers of Polyoxyethylene and Polylactide with Different Architectures

Diblock and triblock copolymers were prepared from polyethylene glycol (PEG, (M) over bar (n) = 2 000), L-lactide and D,L-lactide. A novel method was developed to prepare high-molecular-weight multiblock copolymers by transesterification of a PEG/succinic acid polyester with poly(L-lactide). Molecular weights were monitored by GPC and overall composition was checked by H-1 NAAR. Crystallinity, bulk microstructure, and the glass transition were investigated by DSC and simultaneous SAXS/WAXS/DSC, and surface properties by measurement of advancing contact angle. It is found that the crystallization of the poly(ethylene oxide) (PEO) block is very much affected by the position of the PEO block in the copolymer and by the length and the state of the polylactide block. Both DSC and WAXS showed that the crystallization of PEG2000 block was very much suppressed when covalently bonding to polylactide (PLA) blocks. These methods also confirmed good miscibility between amorphous PLA and PEG blocks. The preparation of fiber by electrospinning demonstrates the target application of the multiblock copolymers in tissue engineering.