Thermodynamics of chain-molecule mixtures : heats of mixing of linear methylsiloxanes

Abstract

Heats of mixing have been obtained at 25" for the following mixtures of linear methylsiloxanes : hexamethyldisiloxane (dimer)-octamethyltrisiloxane (trimer) ; dimer-tetramer ; dimer-pentamer ; trimer-pentamer and dimer-polymer. The heats are consistent with the Prigogine cell theory for the thermodynamics of chain-molecule mixtures and with Bramsted's principle of congruence. Two assumptions concerning the volume dependence of the configurational energy of a liquid were tested : that of a van der Waals liquid which gave good results and a 6-12 model which gave poor results. Two excess volume results were also in accord with the former model. The relation between the Prigogine cell theory and the recent theory of Flory, Orwoll and Vrij is examined.

The statistical thermodynamics of mixtures

“…It is reasonable, and can be supported by plausible but not rigorous arguments, that r, q and c should serve as reduction parameters for obtaining the reduced volume, energy and entropy, respectively, of a chain molecule [49][50][51] . Thus a reduced volume V at a reduced temperature of f = (c/r)(kT/s) (8.48) is defined by…”

Simple dilatometer for polymer density and thermal expansivity measurements

“…However, thermal expansivity data of the required accuracy over a sufficiently wide temperature range are available for only a small number of common polymers (e.g., Refs. [2][3][4][5][6][7][8][9].…”

Role of Free Volume Change on Polymer Solutions; Osmotic Pressure of Moderately Concentrated Polyisobutene–Normal Alkane Systems

“…As suggested by Patterson, et al, 12 the free volume theory of Flory, et al, 18 should be a particular case of the Prigogine theory with the choice of exponents m-n as 3-oo. According to this theory, x, is expressed as…”

“…The free volume theory gives a picture much different from the Flory-Huggins theory for the solution properties. Nevertheless many recent investigations by Patterson, et a/.,[5][6][7][8][9][10][11][12][13][14][15] et al,[16][17][18][19][20][21][22][23][24][25][26][27][28] are based on the free volume theory.The residual chemical potential parameter x presented by Flory 18 for a polymer solution depends on the dissimilarity of either the cohesive energies or the free volumes between segments of polymer and solvent molecules. Hence it is expected that measurement of x for various polymer-solvent systems gives significant information for understanding the solution thermodynamics.…”