Synthesis And Properties Of Side-chain Functionalized Polyester

Biodegradable polyesters such as poly(glycolide)(PGA), poly(L-lactide)(PLA),poly(ε-caprolactone)(PCL) and their copolymers have found wide applications insutures, tissue engineering, bone fixation, and controlled drug delivery due to theirexcellent biocompatible and biodegradable properties. However, the lack of functionalpendants and weak hydrophilicitiy limited their further vast biomedical applications.Thus the preparation of biodegradable aliphatic polyesters containing pendantfunctional groups has attracted considerable attention in the past decade. Theavailability of functional groups along the polymer chains is highly desirable for finetuning the polymer properties, such as hydrophilicity, biodegradability, permeabilityand so forth. Particularly, it provides an opportunity for covalently attaching drugs andother bioactive reagents onto the polymers, which is expected to facilitate a variety ofpotential biomedical applications. In this thesis, a series of functional cyclic monomerswere synthesized, and a new type of amphiphilic block copolymer was prepared byring-opening polymerization and using mPEG as the macroinitiator. These functionalpolymers are promising to be used as targeted and controlled delivery systems andintelligent tissue engineering scaffolds after conjugation with bioactive reagents. Themain results were listed as follows:1. New L-malic acid-O-carboxylanhydride (L-malOCA) monomers containingfunctional groups were successfully prepared by a four-step reaction usingL-malic acid as a starting material. The chemical structure of monomer wascharacterized by1HNMR,13CNMR and FTIR. Presence of these functional groupsis expected to facilitate further modifications of the polymer, such as attachingdrug molecules, short peptides and oligosaccharides.2.(3S)-[(benzyloxycarbony)ethyl]-1,3-dioxolane-2,5-diones (L-gluOCA/BED)was synthesized. mPEG-b-PBED was successfully prepared by ring-openingpolymerization (ROP) of L-gluOCA in the presence of poly(ethylene glycol)monomethyl ether (mPEG) as a macroinitiator using4-dimethylaminopyridine(DMAP) as catalyst. Subsequent catalytic hydrogenation using10%Pd/C ascatalyst led to the formation of corresponding amphiphilic copolymermPEG-b-PED with pendant carboxyl groups.