Comparing the Performance of Computational Estimation Methods for Physicochemical Properties of Dimethylsiloxanes and Selected Siloxanols

Abstract

Siloxanes are used in high amounts in a wide range of applications. There is evidence that siloxanes may be persistent and bioaccumulative in the environment. Despite their high production volumes and their wide applications, only few empirical data on their physicochemical properties are available. For a selection of linear and cyclic siloxanes and siloxanols, we computed (subcooled) liquid vapor pressure, (subcooled) liquid water solubility, and the partition coefficients among air, water, and octanol with the property estimation methods, EPI Suite, SPARC, and COSMOtherm and compared the results to experimental data from the literature. The estimates obtained with the three methods generally show decent qualitative and limited quantitative agreement in the estimated trends of property data for the homologous series of linear and cyclic dimethylsiloxane oligomers. The number of measured property data available in the literature is small, but the data show considerable scatter, and their ranges exceed the differences among the three estimation methods in several cases. A strong impact of molecular configurations and conformations on substance properties could be demonstrated by means of COSMOtherm. In a case study we illustrate that these effects are large enough to greatly influence the environmental fate of the transformation products of octamethylcyclotetrasiloxane (D 4 ).

Comprehensive atmospheric modeling of reactive cyclic siloxanes and their oxidation products

“…This work builds on the limited information available on the oxidation products. Properties relevant to fate and transport (e.g., Henry’s law coefficient) have been predicted in this work and in others based on structure activity relationships (Buser et al, 2013b; Whelan et al, 2004). Latimer et al (1998) measured equilibrium gas–particle partitioning of D 5 and D 4 TOH on diesel, wood, coal soot, and Arizona fine dust aerosols.…”

Silicon is a Frequent Component of Atmospheric Nanoparticles

“…Previous modeling has included 3-D atmospheric modeling of D 5 at hemispheric scales, ,, global modeling of D 5 using a multimedia mass balance model at 15° resolution, , box modeling of D 4 and D 5 , global multimedia fate and transport modeling using a zonally averaged global model, , and box modeling (including partitioning to cloud droplets and aerosols) over the U.S. of D 4 including proposed multiple generations of reaction products . Calculated partitioning properties and subsequent multimedia partitioning behavior for cyclic siloxanes and oxidized reaction products based on structure activity relationships have also been investigated. − In this work, the three most common cyclic siloxanes used in personal care products (D 4 , D 5 , and D 6 ) as well as the corresponding oxidized reaction products were modeled for the continental U.S. using CMAQ.…”

Comprehensive Atmospheric Modeling of Reactive Cyclic Siloxanes and Their Oxidation Products

“…Properties relevant to fate and transport (e.g. Henry's law coefficient) have been predicted in this work and in others based on structure activity relationships (Buser et al, 2013b;Whelan et al, 2004). Latimer et al (1998) measured equilibrium gas particle partitioning of D5 and D4TOH on diesel, wood, coal soot, and Arizona fine dust aerosols.…”