The phase transition behavior of poly(butylene adipate) (PBA) crystals in its blends with poly(vinyl phenol) (PVPh) was investigated by infrared (IR) spectroscopy and X-ray diffraction (XRD). The IR and XRD studies indicate that the hydrogen bonding between the C=O group of PBA and the OH group of PVPh developed in the PBA/PVPh blends with the ratios of 80/20 and 50/50 does not influence the solution crystallization behavior of PBA: The phase transition behavior of PBA in the blends is, however, significantly altered by the blending. In the net PBA, linear changes of the intensities of IR bands at 1077, 930, and 910 cm(-1) are observed in the temperature range of 25-47.5 degrees C followed by an abrupt Change corresponding to the occurrence of beta-to-alpha phase transition: In the blends, the accelerated intensity, changes of the those Ilk bands occur before the beta-to-alpha phase transition, which is contributed to the melting of imperfect beta-PBA crystals at relatively lower temperature. In addition, the significantly depressed beta-to-alpha phase transition temperature is also identified.