Tailor-Made Amphiphilic Biodegradable Polymer-Gels: 1. Gel Preparation via Controlled Ring-opening Polymerization Using Glucopyranoside As Initiator and Subsequent Coupling with alpha,[omega]-Bifunctional PEG

Novel amphiphilic and biodegradable gels composed of glucopyranoside, poly ([epsilon]-caprolactone) (PCL, n=25-63), and poly (ethylene glycol) (PEG, m=3) were synthesized. Methyl 2,3-di-O-benzyl-alpha-D-glucopyranoside was used as an initiator for ring-opening polymerization (ROP) of [epsilon]- caprolactone ([epsilon]-CL). The primary hydroxyl group (6-OH) in the above sugar derivative acted chemoselectively as the initiator for living ROP of [epsilon]-CL, yielding sugar-headed PCL with various lengths of PCL-chains. The polymerization temperature (60 degree C) is very important to suppress the competitive initiation reaction from the secondary hydroxyl group (C4-OH). In order to prepare the cross-linker, both alpha and [omega]-termini of PEO (n=3 and 23) were converted to dicarboxylic chlorides, which actually acted as a coupling reagent for tailor-made amphiphilic biodegradable gel having a sequence of 'Sugar-PCL-PEG-PCL-Sugar.'