Evaluation of enthalpy of mixing by calorimetric method: effect of hydrogen bonding in poly(4-hydroxy styrene) based blends

To verify the effect of hydrogen bonding on the polymer mixing, blends of poly(vinyl methyl ether) (PVME) and poly(methyl methacrylate) (PMMA) with poly(4-hydroxy styrene) (PHS), respectively, have been prepared. The effect of hydrogen bond strength on the enthalpy of mixing, DHM, was investigated by microcalorimetric measurements and FTIR spectroscopy. Infrared analysis allowed to measure the amount of hydrogen bonding by a curve fitting procedure in PHS/ PMMA blends, looking to the change in the characteristic bands of carbonyl group of PMMA. In the case of PHS/PMVE, the hydroxyl-stretching region has been investigated to have only a qualitative estimation of hydrogen bonding. For both PHS/PMVE and PHS/PMMA systems, the measured exothermic (negative) DHM decreases with the increase in the PHS content, indicating that the presence of strong specific intermolecular interactions, such as hydrogen bonding, favours the polymer blending.