Thermodynamic and kinetic analysis of phase separation of temperature-sensitive poly(vinyl methyl ether) in the presence of hydrophobic tert-butyl alcohol

NMR and isothermal titration calorimetry (ITC) techniques were chosen to examine interactions in a poly(vinyl methyl ether) (PVME)/tert-butyl alcohol (t-BuOH)/water ternary system. The effects of PVME and t-BuOH concentrations on phase separation temperature were examined. Molecules of t-BuOH additive hydrophobically associate with PVME and decrease the phase separation temperature. Thermodynamic parameters connected with phase separation were calculated from NMR results using an approach based on the van’t Hoff equation. Presence of t-BuOH increases the number of PVME monomeric units in one cooperative domain (where the units undergo phase separation as whole—‘all-or-none’). NMR time-resolved relaxation measurements show very different dynamics of the solvent releasing process for low and high PVME concentrations above phase separation temperature. ITC data show that the presence of t-BuOH restricts water solvation of PVME globules. Presented results on the PVME/t-BuOH/D₂O system show that the PVME solution properties are not constant in time. The analysis of measurements (and resulting properties) should always be done while considering strong time-dependent behaviour of PVME solutions.