Analysis of Mesoscopic Structured 2-Propanol/Water Mixtures Using Pressure Perturbation Calorimetry and Molecular Dynamic Simulation.
In this paper we demonstrate the application of pressure perturbation calorimetry (PPC) to the characterization of 2-propanol/water mixtures. PPC of different 2-propanol/water mixtures provides two useful measurements: (i) the change in heat (ΔQ); and (ii) the [Formula: see text] value. The results demonstrate that the ΔQvalues of the mixtures deviate from that expected for a random mixture, with a maximum at ~20-25 mol% 2-propanol. This coincides with the concentration at which molecular dynamics (MD) simulations show a maximum deviation from random distribution, and also the point at which alcohol-alcohol hydrogen bonds become dominant over alcohol-water hydrogen bonds. Furthermore, the [Formula: see text] value showed transitions at 2.5 mol% 2-propanol and at approximately 14 mol% 2-propanol. Below 2.5 mol% 2-propanol the values of [Formula: see text] are negative; this is indicative of the presence of isolated 2-propanol molecules surrounded by water molecules. Above 2.5 mol% 2-propanol [Formula: see text] rises, reaching a maximum at ~14 mol% corresponding to a point where mixed alcohol-water networks are thought to dominate. The values and trends identified by PPC show excellent agreement not only with those obtained from MD simulations but also with results in the literature derived using viscometry, THz spectroscopy, NMR and neutron diffraction.
Department of Chemical & Biological Engineering, ChELSI Institute, University of Sheffield, Sheffield, S1 3JD England, UK.
Jordan W
JW
Bye
Department of Material Science & Engineering, University of Sheffield, Sheffield, S1 3JD England, UK.
Colin L
CL
Freeman
Department of Chemical & Biological Engineering, ChELSI Institute, University of Sheffield, Sheffield, S1 3JD England, UK.
John D
JD
Howard
Department of Chemical & Biological Engineering, ChELSI Institute, University of Sheffield, Sheffield, S1 3JD England, UK.
Gregor
G
Herz
Department of Chemical & Biological Engineering, ChELSI Institute, University of Sheffield, Sheffield, S1 3JD England, UK.
James
J
McGregor
Department of Chemical & Biological Engineering, ChELSI Institute, University of Sheffield, Sheffield, S1 3JD England, UK.
Robert J
RJ
Falconer
Differential scanning calorimetry; Heat capacity; Isopropanol; Molar expansivity; Thermal expansion coefficient