Temperature Dependence Of Dipole Moment Research Articles

Studies of linear polymer dimensions of poly(4‐chlorostyrene) in various solvents around the θ temperatures by intrinsic viscosity

AbstractIntrinsic viscosities of poly(4‐chlorostyrene) solutions in isopropyl‐benzene and n‐propylbenzene at temperatures above and below the theta (θ) temperatures of these solvents were measured using a capillary viscometer. The viscosity measurements were performed on three poly(4‐chlorostyrene) samples having molecular weights (M̄;v) 1.75 × 106, 6.5 × 105 and 2.7 × 105. A smooth and continuous contraction below the θ temperatures was observed for both solvents. The temperature dependence of [/eta] can be represented by a master curve in a plot of α3/eta|/tau|M1/2 (g1/2 mol−1/2) versus |/tau|M1/2 (g1/2 mol−1/2), where α/eta = [/eta(T)]/[/eta(θ)]1/3 is the expansion factor and /tau = (T ‐ θ)/T is the reduced temperature. A universal plot of reduced viscosity size (α/eta) versus reduced blob parameter (N/Nc) shows the achievement of collapsed state for T<θ. The prediction of thermal blob theory is also verified for T > θ. The temperature dependence of intrinsic viscosity, both below and above the θ temperature, exhibits similar behaviour to the temperature dependence of dipole moments for both of these solvents.

A Study of the Conformational Equilibria of Pyridinealdehydes in Decahydronaphthalene Solution

AbstractA study of the temperature dependence of the electric dipole moment of 2‐, 3‐, and 4‐pyridinealdehyde in dilute decahydronaphthalene solution over the temperature region of 25 °C to 100°C has been carried out. From the temperature dependence of the dipole moment it is concluded that the ON‐trans conformation of 2‐pyridinealdehyde and 3‐pyridinealdehyde is more stable than the corresponding ON‐cis conformation by ∼ 3.7 kJ mol−1 and ∼ 1.4 kJ mol−1 respectively.

Lösungsmittelbedingte Temperaturabhängigkeit des Dipolmoments polarer Molekeln in apolaren Medien

AbstractSolute‐solvent interactions of polar molecules generally result in an apparent temperature dependence of dipole moments. Variations of the dielectric constants with temperature of solutions of mono‐ and 1,2‐dichlorobenzene in different apolar solvents confirm the repeatedly observed solvent‐influenced apparent temperature dependence of the dipole moments. An attempt has been made for the first time to interpret these temperature effects on the basis of a statistical (Monte‐Carlo‐Method) and a continuum model. Both models permit the description of the typical curve of the dipole moments as a function of temperature and in addition reproduce the observed effects as to the order of magnitude.