This presentation deals with a mixture consisting of predominantly non-polar macromolecule, poly (propylene glycol), PPG, and a small polar molecule, water. A true mixture can be formed only if the two interact via hydrogen bonding, between the oxygen atom on PPG backbone and water, as confirmed via IR spectroscopy and solubility study. Density measurements versus molar fraction revealed a positive deviation from linearity that becomes more pronounced as temperature decreases. In temperature interval from -30oC to 25oC, the thermal expansion coefficient for pure PPG (-8.182 g cm-3 K-1) linearly depends on temperature. As the molar fraction of water increases, this coefficient increases and its temperature dependence becomes non-linear (1). The viscosity versus molar fraction was also found to deviate from ideal behavior; the best fit at 20oC was obtained using the McAllister equation (2). The viscosity temperature dependence is more complicated and is under a scrutiny now. When water molecules were hydrogen bonded to PPG, the glass transition temperature was found to slightly decrease as the water content increased. As the mixture was precooled, the water became separated from PPG and formed crystallites making the glass transition temperature independent on water content. Differential scanning calorimetry technique and luminoprobes were used to complete the liquid-solid phase diagram. The effect of molar mass of PPG on physicochemical properties of this mixture will also be reported.

Binary mixtures consisting of glass-forming constituent and crystal-forming constituent: Density, rheology and phase transitions in poly(propylene glycol) – water system

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.