Enzymatically prepared novel polyphenol poly(4,4'-dihydroxydiphenyl ether) (PDHDPE) is blended to modify the properties of biodegradable polyester poly(epsilon-caprolactone) (PCL). Since the differential scanning calorimetry data show single composition-dependent glass transition for each blend, PCL and PDHDPE are found to be miscible in the amorphous phase. The crystallization of PCL is depressed by PDHDPE because PDHDPE reduces the molecular mobility and the flexibility of molecular chains of PCL. The Fourier transform infrared spectra clearly indicate that PCL and PDHDPE interact through strong intermolecular hydrogen bonds formed between the carbonyl groups of PCL and the hydroxyl groups of PDHDPE. The increase of the long period, calculated on the basis of Bragg's law with the measurement of small-angle X-ray scattering, is found because the peak position of the profiles of Lorentz-corrected intensity shifts to smaller angle. With the help of lamellar stack model and one-dimensional correlation function, the accurate lamellar parameters are calculated. The increase of long period is induced by the increase of crystal thickness. The thermal treatment can effectively modify the thermal stability of PCL/PDHDPE blends with the introduction of an intermolecular coupling of the polymer to give crosslinked and/or branched products. It is also found that the addition of PDHDPE to PCL would obviously increase the Young's modulus of PCL. (c) 2006 Wiley Periodicals, Inc.