Dynamic homogeneity in mixtures of poly(vinyl methyl ether) with low molecular weight phenolic molecules

Dynamical homogeneity was observed in mixtures of PVME with two small molecules-4-ethylphenol [EPh] and bis(4-hydroxyphenyl)methane [BPM]-by broadband dielectric spectroscopy. TTS is valid in mixtures with EPh concentrations up to 50% and for BPM content from 2 to 30%, and all have the same segmental relaxation time distribution as neat PVME. This behavior is attributed to the strong intermolecular hydrogen bonding, increased mixing entropy, relatively small T_g contrast, the absence of self-concentration effects, and reduced interchain cooperativity. However, PVME/toluene mixtures exhibit a slightly broader segmental relaxation distribution due to the absence of hydrogen bonding. We also found that strong intermolecular associations are capable of slowing down the secondary relaxation of PVME. Spatial heterogeneity is expected in mixtures with very low BPM contents based on the effect of stoichiometry, and two relaxing segments are possible in 2% BPM/PVME mixtures.