Probing the micro-phase separation of thermo-responsive amphiphilic polymer in water/ethanol solution

The temperature-induced coil-globule transition (micro-phase separation) in water/ethanol solutions of poly(vinyl methyl ether) was studied using NMR spectroscopy, differential scanning calorimetry, optical microscopy and dynamic light scattering. NMR sequence based on spin-echo was introduced in order to determine lower critical solution temperature with high accuracy. Variation in DSC profiles and enthalpy increments depending on ethanol concentration in a water/ethanol mixture was found. Evolution of morphology pattern during heating-cooling cycle was observed using optical microscopy. At lower PVME concentration the globule size distribution was determined using digital image processing. Relative number and relative mass size distributions of globules in a dilute sample were measured by differential scanning calorimetry and subsequently compared with those obtained by optical microscopy.