Posted in Contact Angle, D L Williams, Hansen Solubility Parameters, Physical Chemistry, Solubility, Solvent Blending

Hansen Solubility Parameters via QSPR

Williams, D. L.; Kuklenz, K. D. A QSAR Model for Predicting Solvents and Solvent Blends for Energetic Materials, Proceedings of the International Annual Conference of ICT, 40th (Energetic Materials), Karlsruhe, Germany, 2/1-2/11, (2009)

Researchers in the paint and polymer industry have shown that the Hansen solubility parameters (HSP) are useful for predicting suitable solvents for the filled-polymer formulation process. To apply this work to the high explosive formulation process, the HSPs of the various energetic materials must be determined or predicted.

A quantitative structure activity relationship (QSAR) was developed that is based upon the output of a density functional theory optimization and frequency calculation (B3LYP/6- 31G(d)//B3LYP/6-31G(d)) using the Gaussian 03 computational package. Structural parameters were extracted from the Gaussian output files of each molecular species. These consisted of the geometric mean of the exact polarizability tensors (α , Å3), the dipole moment (μ, Debye) the highest occupied molecular orbital energy (HOMO, Hartree), the number of each type of atom, and the delta charge (Δq) – defined as the difference between the most negative heteroatom and the most positive hydrogen in the molecule. The value of Δq = 0 was given to hydrocarbons by fiat. A stepwise linear regression was used to determine the correlation of these inputs and mathematical transformations of these inputs to the HSPs for a training set of 54 solvents and nitrated compounds. The resulting QSAR matrix was then applied to 23 energetic materials and precursors yielding the HSPs (δD, δP, δH) in MPa1/2.

The HSPs were also determined for HMX, RDX, PETN, and HNS using experimental solubility data and the group additivity methods of Van Krevelen and Stefanis. The QSAR model outperformed the group additivity methods in matching the experimentally determined HSPs using the Hansen distance parameter (Ra) as the figure of merit.

En route to the QSAR model, a very simple model of molar volume was developed wherein the molar volume is computed directly from the molecular formula CaHbNcOdSePfFgClhBri via the following equation: Vm = 12.53 + 8.77a + 3.96b + 4.87c + 6.12d + 17.22e + 19.45f + 9.70g + 18.66h + 20.74i. The correlation of this equation with the literature values of 183 molecules was 99.67% with an R2 = 0.9847 over a range of 400 cm3/mol.

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Posted in Contact Angle, D L Williams, Hansen Solubility Parameters, Solubility

Solubility Spheres

When working with industrial scale recrystallizations, a few more grams per liter improvement in solubility can save a substantial amount of time and MONEY. 

Williams, D. L.; Kuklenz, K. D., A Determination of the Hansen Solubility Parameters of Hexanitrostilbene (HNS), Propellants Explosives and Pyrotechnics, 34(5), 452-457, (2009) 

Abstract
The temperature-dependent solubility of hexanitrostilbene (HNS) [CAS# 20062-22-0] was determined in ten solvents and solvent blends using the Tyndall effect. Thermodynamic modeling of the data yielded Flory interaction parameters, the molar enthalpy of mixing, the molar entropy of mixing, and the molar Gibbs energy of mixing. All solutions exhibited endothermic enthalpies and positive entropies of mixing. The presence of water in some of the solvent blends made dissolution increasingly endothermic and disfavored solubility. The solubilities of HNS at 25 °C were used to determine the three-component Hansen solubility parameters (HSP) (δD=18.6, δP=13.5, δH=6.1 MPa1/2) and the radius of the solubility sphere (R0=5.8 MPa1/2). The HSP determined for HNS using group-additivity (δD=21.0, δP=13.3, and δH=8.6 MPa1/2) also correctly predicted the optimum solvents for this explosive.

Posted in Contact Angle, Education, Hansen Solubility Parameters, Physical Chemistry

Surface Tension and Density Determination

When moving into our new chemistry building, my graduate student uncovered a relic made in the 1930’s.  It was a cast-iron Du Nuoy ring tensiometer, but we didn’t know that.  We guessed that it had something to do with surface tension, and he did a literature search.  Up popped a 1930’s paper by Harkins and Jordan on the ring method for determining surface tension. 

Continue reading “Surface Tension and Density Determination”

Posted in Contact Angle, D L Williams, Hansen Solubility Parameters, Solvent Blending

Chemically-Resistant Glove Selection

Background

As a college chemistry student I was eager to read the labels on every product I could find to bask in my newfound knowledge of organic nomenclature.  Imagine my frustration when I found more useful information on a bottle of shampoo than I found on a can of Lacquer Thinner.  Fortunately, labelling has improved, and most major components can be found on the sides of the can.

Still, I suffered with the lingering question of “Why did they mix toluene and MEK to make product X?”.  It was an exciting day in 2006, when a student came into the office and asked me why I wasn’t using the Hansen Solubility Parameters to pick solvents.  I had sent her on a literature search for solubility models, and she found the Hansen Solubility Parameters Handbook 1st Edition.  (Don’t be too hard on me.  I was raised as a vibrational spectroscopist and had little experience in solubility studies.)  A quick view of the book gave me a “Eureka” moment, as I found ways to blend solvents, and “stick non-stick surfaces to a surface”. 

I have been modelling solvent blends for recrystallization, precision cleaning, and polymer swelling for about 3 years.  Much of my initial work was in an Excel spreadsheet using the equations in the CRC Handbook on the Hansen Solubility Parameters.  But I eventually “graduated” to using the HSPiP software and eBook1 available at http://www.hansen-solubility.com/

Glove Selection

Perhaps your lab is typical in selecting nitrile gloves for everything.  Changes are made when one loses a finger (of a glove) in a beaker of solvent.  This is not the best practice, but many will not believe me when I say that there is an “easy alternative” to the “lost-finger” selection scheme.  Continue reading “Chemically-Resistant Glove Selection”