Synthesis and characterization of biodegradable poly(ester anhydride) based on -caprolactone and adipic anhydride initiated by potassium poly(ethylene glycol)ate

Novel biodegradable poly(ester anhydride) block copolymers based on -caprolactone (-CL) and adipic anhydride (AA) were prepared by sequential polymerization. -CL was first initiated by potassium poly(ethylene glycol)ate and polymerized into active chains (PCL-O-K+), which were then used to initiate the ring-opening polymerization of AA. The effects of the AA feed ratio, solvent polarity, monomer concentration, and temperature on sequential polymerization were investigated. The copolymers, obtained under different conditions, were characterized by Fourier transform infrared, 1H NMR, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). The GPC results showed that the weight-average molecular weights of the block copolymers were approximately 6.0 × 104. The DSC results indicated the immiscibility of the two component