Synthesis And Study Of Dendronized Polymers Based On Polyethylene Glycol Terminated By Polyester Dendrons

Polyester dendrimers/dendrons with excellent biocompatibility is the one and only biodegradable dendrimer which has shown high potential in controlled drug delivery system and tissue engineerring. Divergent synthetic method has been applied in this study to synthesis the first-fourth generation macro-initiator polyethylene glycol terminated by polyester dendrons with different amounts of hydroxyl groups and the dendronized polymers based on these micro-initiators have also been investigated. The study has been divided into three parts:(1) Synthesis and study of dumbbell-shaped tri-block copolymer consisting of polycaprolactone and poly(ethylene glycol)A series of well-defined dumbbell-shaped tri-block copolymers consisting of comb-like polycaprolactone (PCL) and linear poly(ethylene glycol) (PEG) with narrow molecular weight distributions and varied PCL arm lengths have been synthesized via the sequential preparation of terminal dendronized polyhydric PEG and ring-opening polymerization ofâ–¡-caprolactone (CL). The length of PCL arms can be readily controlled by the feed molar ratio of CL monomer to the hydroxyl groups in PEG macro-initiator.(2) The influence of branching degree and molecule weight on the thermol properties,crystallization and biocompatibilities.A series of copolymers with the same molecule weight and different branching degree and a series of copolymers with the same branching degree and different molecule weight were synthesized to evaluate the interrelationship of branching degree and molecule weight to thermol properties,crystallization and biocompatibilities of copolymers. And the results showed that the melting point and the crystallization temperature shifted to lower temperature with the increasing of branching degree when that series of copolymers had the same molecule weight, but the Tg of copolymers first increased within a narrow range and then decreased by a wide margin. When other series of copolymers had the same branching degree, the melting poin,Tg and crystallization temperature shifted to a higher temperature with the increasing of molecule weights of copolymers.(3) The preparation of microspheres loading drug and the study of drug release in vitro.The emulsion solvent evaporation method and the double emulsion solvent evaporation method were respectively used to prepare the copolymer microspheres loading paclitaxel and temozolomide based on the fourth generation dumbbell shaped tri-block copolymers. We evaluated the influence of preparation process of microspheres on the surface shape,size and entrapping drug amount of copolymers microspheres and studied the drug releasing curves of microspheres in PBS solution. The test results showed that both microspheres loading paclitaxel and temozolomide had the effect of controlled release and the controlled releasing time were higher than 15 days.