AbstractIn order to clarify the effects of phenols on properties of polyesters, the blends of poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) with 4,4′‐dihydroxydiphenylpropane (BPA) and p‐tert‐butylphenol (TBP) were studied. The FTIR spectra revealed that there was strong hydrogen‐bond (H‐bond) interaction between PHBV and both phenols. By evaluating the fraction of H‐bonded CO in the blend, it was concluded that BPA showed a stronger tendency than TBP to form H‐bonds with PHBV. Accordingly, BPA formed a stronger suppression than TBP on the crystallization of PHBV. When 30 wt% BPA or 50 wt% TBP were added into PHBV, the crystallization of PHBV was completely suppressed in the DSC cooling scan. As the phenol content was increased, the Tg of PHBV/TBP blend decreased while the Tg of PHBV/BPA blend increased. This difference indicated that TBP and BPA acted as plasticizer and physical crosslinking agent, respectively. Copyright © 2004 Society of Chemical Industry