Blends of chitosan and poly(epsilon-caprolactone-co-2-oxepane-1,5-dione) (PCO) were fabricated by solvent casting technique using 77% acetic acid as the cosolvent. The interactions between chitosan and PCO were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and differential scanning calorimetry. The miscibility became poorer with increase of PCO from 50% to 75%, which was supported by the FloryHuggins interaction parameter and crystallinity of PCO. According to X-ray pattern, crystallinity of CS became weaker when PCO content was improved. Results indicated that there existed stronger interactions in comparison with PCL/CS blends. Therefore, the addition of functional polyester PCO made the brittle chitosan ductile. The elongation was significantly prolonged to 21.60 +/- 4.92% with the break stress maintaining about 32 MPa, better than that of PCL blends. The degradation behavior showed slower degradation rate compared with pure CS and the morphology was illustrated by scanning electron microscopy. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013