Study of hydrogen-bonding strength in poly(ε-caprolactone) blends by DSC and FTIR

The hydrogen-bonding strength of poly(epsilon -caprolactone) (PCL) blends with three different well-known hydrogen-bonding donor polymers [i.e., phenolic, poly(vinyl-phenol) (PVPh), and phenoxy] was investigated with differential scanning calorimetry and Fourier transform infrared spectroscopy. All blends exhibited a single glass-transition temperature with differential scanning calorimetry, which is characteristic of a miscible system. The strength of interassociation depended on the hydrogen-bonding donor group in the order phenolic/PCL > PVPh/PCL > phenoxy/PCL, which corresponds to the q value of the Kwei equation. Tn addition, the interaction energy density parameter calculated from the melting depression of PCL with the Nishi-Wang equation resulted in a similar trend in terms of the hydrogen-bonding strength. Quantitative analyses on the fraction of hydrogen-bonded carbonyl groups in the molten state were made with Fourier transform infrared spectroscopy for all systems, and good correlations between thermal behaviors and infrared results were observed. (C) 2001 John Wiley & Sons, Inc.