Publication Date:
2013-11-23
Description:
We report an experimental study of ethyl stearate/ethanol binary mixtures employing optical microscopy, rheology, dynamic light scattering, and femtosecond optical Kerr effect spectroscopy. Optical microscopy images show that at 25 °C this mixture is homogeneous up to 10 wt% ethyl stearate mass fraction and it leads to crystallization of ethyl stearate from solution at higher mass fractions. Rheological measurements at 40 °C and 25 °C exhibited an increase in viscosity of the binary mixture with increasing ethyl stearate mass fraction, consistent with molar mass considerations. Moreover, closer inspection of the rheology data from 0 to 10 wt% ethyl stearate mass fraction indicate a plateau in the viscosity near 10%, thus indicating how crystallization affects the rheological properties of the solution, even at 40 °C. Dynamic light scattering data are consistent with two major components at all mass fractions investigated: a small ethyl stearate aggregate consisting of approximately seven monomers and a micron-sized crystallite. Femtosecond time-resolved optical Kerr effect indicates slower nuclear relaxation with increasing ethyl stearate mass fraction, thus suggesting that low-frequency motions of the binary mixture are involved in the early events of crystal nucleation. Copyright © 2013 John Wiley & Sons, Ltd. In order to address the challenge of studying asynchronous non-equilibrium processes with femtosecond spectroscopy, we develop an approach to investigate nucleation in ethyl stearate/ethanol binary mixtures. First, we employ optical microscopy, rheology, and dynamic light scattering to characterize the mixture in non-equilibrated conditions. Femtosecond time-resolved optical Kerr effect indicates slower nuclear relaxation with increasing ethyl stearate mass fraction, thus suggesting that low-frequency motions of the binary mixture are involved in the early events of crystal nucleation.
Print ISSN:
0894-3230
Electronic ISSN:
1099-1395
Topics:
Chemistry and Pharmacology
,
Physics
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