Search results for "Vapor pressure osmometry"
showing 2 items of 2 documents
Branched versus linear oligo(dimethylsiloxane): Differences in their thermodynamic interaction with solvents
2010
The thermodynamic behavior of linear and of branched oligo(dimethylsiloxane) (O-DMS) solutions was studied by means of vapor pressure measurements and vapor pressure osmometry at different temperatures for the thermodynamically favorable solvent THF. The branched material required for that purpose was synthesized and afterwards fractionated by means of the single solvent acetone to eliminate components of low degrees of branching. The Flory-Huggins interaction parameters, χ, for the systems THF/O-DMS as a function of composition pass a minimum at all temperatures (25, 40, and 60 °C) in the case of the branched material. For the unbranched oligomer such a minimum is only observed at 60 °C. A…
Branched Versus Linear Polyisoprene: Flory-Huggins Interaction Parameters for their Solutions in Cyclohexane
2009
Flory-Huggins interaction parameters were determined as a function of composition for solutions of linear and of branched polyisoprene in cyclohexane (CH) at 25, 45, and 65 °C by means of vapor pressure measurements (moderate to concentrated solutions) and by vapor pressure osmometry (dilute solutions). The results demonstrate that CH is a considerably worse solvent for branched polyisoprene than for the linear analog at all temperatures and at all compositions. This observation corroborates the expectation based on a recent phenomenological approach, which accounts explicitly for the incapability of the segments of an individual polymer molecule to spread out over the entire volume of the …