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Modeling the solid-...
Modeling the solid-liquid phase transition in saturated triglycerides
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- Pink, David A. (författare)
- Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada
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- Hanna, Charles B. (författare)
- Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada
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- Sandt, Christophe (författare)
- Department of Chemistry, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada
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- MacDonald, Adam J. (författare)
- Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada
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- MacEachern, Ronald (författare)
- Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada
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- Corkery, Robert W., 1967- (författare)
- YKI, Institute for Surface Chemistry, Stockholm, Sweden
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- Rousseau, Derick. (författare)
- Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada
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Department of Physics, St Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada (creator_code:org_t)
- AIP Publishing, 2010
- 2010
- Engelska.
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 132:5, s. 054502/1-054502/11
- Relaterad länk:
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- We investigated theor. two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al., in which the av. state of each TL mol. in the liq. phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an av. angle of ∌120° between them, and those of (2) Cebula et al., in which the liq.-state conformation of the TL mol. in the liq. phase is a nematic h*-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL mols. are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temps., and in either a Y conformation or an h* conformation in the liq. state at temps. higher than the phase-transition temp., T* = 319 K. We defined an h-Y model as a realization of the proposal of R. Corkery et al. (2007), and explored its predictions by mapping it onto an Ising model in a temp.-dependent field, performing a mean-field approxn., and calcg. the transition enthalpy ΔH. We found that the most plausible realization of the h-Y model, as applied to the solid-liq. phase transition in TL, and likely to all satd. triglycerides, gave a value of ΔH in reasonable agreement with the expt. We then defined an alternative h-h* model as a realization of the proposal of D. J. Cebula et al. (1992), in which the liq. phase exhibits an av. symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h* model gave a value of ΔH that was too small by a factor of ∌3-4. We also predicted the temp. dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman bands in the temp. range of -20° ≀ T ≀ 90°. The exptl. results were in accord with the predictions of the h-Y model and support the proposal of that the liq. state is made up of mols. that are each, on av., in a Y conformation. Finally, we carried out computer simulations of minimal-model TLs in the liq. phase, and concluded that although the individual TL mols. are, on av., Y conformers, long-range discotic order is unlikely to exist.
Ämnesord
- NATURVETENSKAP -- Kemi -- Annan kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences -- Other Chemistry Topics (hsv//eng)
Nyckelord
- modeling solid liq phase transition satd triglyceride
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