Synthesis and characterization of novel biodegradable crosslinked polyesters

The second route of synthesis involved a two-part system: an amine-terminated prepolymer and poly(ethylene glycol) diglycidyl ether (PEG-diglycidyl ether).In this work, two prepolymers were chosen: Poly(caprolactone) (PCL) of molecular weight 3000 xiii g/mol and a random 50/50 copolymer, poly(caprolactone-co-d,l-lactide) of molecular weight 18000 g/mol.These prepolymers were successfully synthesized and characterized.The crosslinkers used for the subsequent crosslinking were PEG diglycidyl ether of two lengths: 500 g/mol and 1000 g/mol.Four different crosslinked polymers of gel contents of 40-50 % by mass were successfully synthesized and characterized.It was found that the longer the PEG crosslinker used, the higher the amount of swelling exhibited and hence the faster the initial rate of hydrolytic degradation.It was also noted that the longer the prepolymer, the lower the crosslink density, hence the longer the maximum elongations attained by the crosslinked polymer.The Young's moduli of these polymers ranged from around 10-35 kPa.Two of the polymers were chosen for a cyclic tensile test and complete recovery with zero hysteresis was seen over 3 cycles up at a certain strain level.This is one of the most important advantages of chemically crosslinked polymers.Extracts of all the polymers were taken for cytotoxicity testing and it was shown that the polymers were non-toxic to cells over 24 h.Hence this two-part epoxy-amine series of polymers have shown to be a highly tailorable system, with properties suitable for future applications in soft tissue engineering.Chapter One