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

Abstract

Diblock and triblock copolymers were prepared from polyethylene glycol (PEG, $\overline M _{\rm n}$ = 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 1H NMR. 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.magnified image

Amphiphilic multiblock copolymers of PLLA, PEO and PPO blocks: Synthesis, properties and cell affinity

“…required biomaterial properties for a specific application [7][8][9]. Copolymerization may modulate these properties by varying hydrophilic/hydrophobic and amorphous/crystalline ratios [10].…”

“…The synthesis of diblock PLLA-b-PEO and triblock PLLAb-PEO-b-PLLA copolymers for biomedical applications has been continuously reported in prior decades, particularly in drug delivery systems, biocompatible coatings and electrospun scaffolds [7,11,12]. Block copolymers comprising PLLA and PPO blocks were studied as biodegradable copolymers by Kimura et al [13].…”

PLA–PEO–PLA Hydrogels and Their Mechanical Properties

“…This had a larger impact on amorphous PRLA materials than on containing crystalline PLLA [46]. Triblock formation begins by ring-opening polymerization of the lactide monomer by a preformed dihydroxylated PEG [49][50][51][52][53][54]. Catalysts such as stannous octoate, SnO, SnO 2 , Sb 2 O 3 , PbO, GeO 2 , SnCl 2 , and NaOH have been used [50,52,[55][56][57][58][59][60].…”

Synthetic Strategies for Biomedical Polyesters Specialties

“…The molecular weight of the resulting copolymer can be significantly increased starting from precursors of higher molecular weight. Using succinic acid as chain extender for poylethylene glycol, poly(L-lactide) and poly(D,L-lactide) of high molecular weight and titanium isopropoxyde as transesterification catalyst, molecular weight up to 40 000 g/mol vs. polystyrene standards could be achieved (Mai et al 2009). …”