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Low pressure liquid-liquid demixing data for polystyrene dissolved in 76 different one-component solvent systems are reviewed and correlated. The phase diagrams are discussed. With only one exception the molecular weight of each solvent is less than that of two polystyrene monomer units. A new relation is developed which quantitatively correlates the area of solubility lying between the UCS and LCS demixing curves in the (T c ' M ~ 112) projection with solvent solubility parameters.

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Nature uses negative pressures in the most resourceful and efficient ways. Yet, negative pressure states are still sometimes considered inaccessible by part of the scientific community. In this paper we show that any condensed phase can exist in absolute negative pressure regimes, while the same is not true for gas phases. We also demonstrate that such states are not merely possible but have, in spite of their metastability, been observed experimentally on numerous occasions. Moreover, physical properties of several substances and mixtures have already been determined in the stretched liquid phase at absolute negative pressures. Nevertheless, conceiving of and succeeding in an experiment that produces high tension in a liquid are rather difficult. Thus, equations of state and computer simulations are powerful tools for studying metastable liquids. By using a simple equation of state we show: how negative pressure regimes can be attained; the maximum intrinsic tension a liquid can sustain; and below which temperature a liquid can be found in this state. Experimental and theoretical work on liquids at negative pressures is reviewed. Furthermore, the similarities and differences between negative temperature and negative pressure states are demonstrated. Due to water's non-trivial behavior as well as its technological and scientific importance, it has been the most studied substance in metastable phenomena. We will thus devote particular attention to some of the rich features of its metastable phase diagram. Water belongs to a class of substances that presents density anomalies. We also show how the negative pressure region of the phase diagram proves to be paramount in understanding the unusual behavior of this class of substances.

Interfacial pressure and density profiles are calculated from molecular dynamics and lattice Boltzmann simulations of a liquid film in equilibrium with its vapor. The set of local values of tangential pressure and density along an interface exhibits a van der Waals-type loop; starting from the stable vapor bulk phase one passes through metastable and unstable states to the stable liquid bulk phase. The minimum and maximum values of the profile of tangential pressure are related to the liquid and vapor spinodal states, respectively. The spinodal pressures turn out to be linearly related to the extreme values of the tangential pressure in the interface. The comparison with equations of state shows good agreement with the simulation results of the spinodals. In addition the properties of the metastable region are obtained. Based on this investigation a method is proposed for the estimation of the liquid spinodal from experimentally obtained interfacial properties. Estimations for water and helium are presented.

The application of a modified Simon-Glatzel-type relation [Z. Anorg. Allg. Chem. 178, 309 (1929)] for the pressure evolution of the glass temperature is presented, namely, Tg(P)=Tg0[1+DeltaP/(pi+Pg0)]1/bexp[-(DeltaP/c)], where (Tg0,Pg0) are the reference temperature and pressure, DeltaP=P-Pg0, -pi is the negative pressure asymptote, b is the power exponent, and c is the damping pressure coefficient. The discussion is based on the experimental Tg(P) data for magmatic silicate melt albite, polymeric liquid crystal P8, and glycerol. The latter data are taken from Cook et al. [J. Chem. Phys. 100, 5178 (1994)] and from the authors' dielectric relaxation time (tau(P)) measurements, which employs the novel pressure counterpart of the Vogel-Fulcher-Tammann equation: tau(P)=tau0P exp[DPDeltaP/(P0-P)], where DeltaP=P-PSL (PSL is the stability limit hidden under negative pressure), P0 is the estimation of the ideal glass pressure, and D(P) is the isothermal fragility strength coefficient. Results obtained suggest the hypothetical maximum of the Tg(P) curve, which can be estimated due to the application of the supporting derivative-based analysis. A hypothetical common description of glass formers characterized by dTg/dP>0 and dTg/dP<0 coefficients is suggested. Finally, the hypothetical link between molecular and colloidal glass formers is recalled.

Preliminary results on the influence of periodically distributed cylindrical nanoinclusions introduced into the f.c.c. hard sphere crystal on its elastic properties and the Poisson's ratio are presented. The nanoinclusions are oriented along the [001]-direction and filled with hard spheres of diameter different from the spheres forming the matrix crystal. The Monte Carlo simulations show that symmetry of the crystal changes from the cubic to tetragonal one. In the case when spheres inside the inclusion are smaller than spheres forming the crystal, the changes of Poisson's ratio are qualitatively similar to the changes observed earlier in the Yukawa sphere crystal, that is, the introduction of nanochannels causes simultaneous decrease of the Poisson's ratio in the [110][1 10]-direction, and its increase in [110][001]-direction. Filling the nanochannel with spheres having diameters greater than that of the spheres in the crystalline matrix, causes a decrease of the Poisson's ratio value from 0.065 down to À0.365 in [111][11 2]-direction. The dependence of the minimal Poisson's ratio on the direction of the applied load is shown in a form of surfaces in spherical coordinates, for selected values of nanochannel particle diameters. The most negative value of the Poisson's ratio found amongst all systems studied was as low as À0.873.