Chain Connectivity and Conformational Variability of Polymers: Clues to an Adequate Thermodynamic Description of Their Solutions, 1

Abstract

This is the first of two parts investigating the Flory‐Huggins interaction parameter, χ, as a function of composition and chain length. Part 1 encompasses experimental and theoretical work. The former comprises the synthesis of poly(dimethylsiloxane)s with different molar mass and the measurements of their second osmotic virial coefficients, A2, in solvents of diverse quality as a function of M via light scattering and osmotic pressures. The theoretical analysis is performed by subdividing the dilution process into two clearly separable steps. It yields the following expression for χo, the χ value in range of pair interaction: χo = α − ζ λ. The parameter α measures the effect of contact formation between solvent molecules and polymer segments at fixed chain conformation, whereas the parameter ζ quantifies the contributions of the conformational changes taking place in response to dilution; ζ becomes zero for theta conditions. The influences of M are exclusively contained in the parameter λ The new relation is capable of describing hitherto incomprehensible experimental findings, like a diminution of χo with rising M. The evaluation of experimental information for different systems according to the established equation displays the existence of a linear interrelation between ζ and α. Part 2 of this investigation presents the generalization of the present approach to solutions of arbitrary composition and discusses the physical meaning of the parameters in more detail.

PEO/CHCl3. Crystallinity of the Polymer and Vapor Pressure of the Solvent. Equilibrium and Nonequilibrium Phenomena

“…Recently is could be explained in terms of chain connectivity and conformational variability of polymers 35,36 . This approach leads in its simplified form to the following uncomplicated expression…”

Polymer Incompatibility Caused by Different Molecular Architectures: Modeling via Chain Connectivity and Conformational Relaxation

“…As expected, the critical Z value required for demixing decreases rapidly as b approaches zero and the branched polymer transforms into a linear product; under these conditions the components are always totally miscible. In addition to Z crit , the critical conditions formulated in Equation (19) and (20) also yield the critical composition. First, calculations concerning the critical compositions were again performed for variable degrees of polymerization of the branched as well as of the linear polymer for b ¼ 0.25.…”

Binary Interaction Parameters, Ternary Systems: Realistic Modeling of Liquid/Liquid Phase Separation

“…[3] Equations (4) and (6) yield the following expression for the experimentally accessible differential interaction parameter x. In Equation (10), the indices 1P are omitted for the sake of simplicity and w stands for the segment fraction of the polymer.…”

“…[1] The main flaws of the original Flory-Huggins theory, are its inability to describe experimental data -like phase diagrams -quantitatively, and to explain some well-documented observations -like the existence of two critical points for binary systems [2] or positive second osmotic virial coefficients, which increase with rising molecular weight. [3] For binary systems, it has already been shown how the shortcomings of the Flory-Huggins theory can be removed without losing the simplicity of the approach. [4] This paper applies this new concept to ternary systems of considerable practical importance.…”