Modeling Polysiloxane Volume and Viscosity Variations With Molecular Structure and Thermodynamic State

Abstract

Siloxanebased polymers (polysiloxanes) exhibit a range of volume, viscosity, and pressureviscosity behaviors that are strongly influenced by the macromolecular structure. In this report, a combination of extant rheological models is applied to develop a molecularrheological modeling formalism that predicts polysiloxane rheological properties, such as specific volume, which means density, viscosity, and pressureviscosity index variations with macromolecular structure, pressure, and temperature. Polysiloxane molecular features are described in terms of alkyl branch length L, pendant type J, density of branch functional monomers Q, and degree of polymerization DP. Both new and published data are used for model parameter determination and validation. Several siloxanebased polymers with alkyl, aryl, alkylaryl, cycloalkyl, and halogenated branches were synthesized to examine the modeled relationship between their molecular structures and rheological behaviors.