Flory temperature and upper critical solution temperature of gelatin solutions

Amarnath Gupta, B. Mohanty, H. B. Bohidar

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36 Citations (Scopus)


The Flory temperatures (θ) measured by turbidity experiments performed on gelatin solutions were found to be 12 ± 0.3, 13 ± 0.3, 14 ± 0.3, 14.5 ± 0.3, and 15 ± 0.3 °C for salt concentrations 0.1, 0.075, 0.05, 0.025, and 0 M (NaCl), respectively. Estimated persistence length (lp) of this weakly charged polyelectrolyte could be deduced from the Benoit and Doty (J. Phys. Chem. 1953, 57, 958) relationship with the approximation that this biopolymer assumes a compact near-globular shape at Flory temperature, implying lp = 9(Rh)2/(5Lm), where Lm is the contour length and Rh is the hydrodynamic radius. It was found that lp ≈ 2.2 ± 0.2 nm at room temperature (20 °C), invariant of salt concentration. The Flory expansion factor (α = Rh(T)/Rh(θ) = 1.5±0.2) was found to be almost constant. θ-Composition for this biopolymer was deduced from turbidimitric titration of aqueous gelatin solutions with the alcohols methanol, ethanol, 2-propanol, and tert-butyl alcohol. It appears that hydrophobic interactions play a crucial role in causing chain collapse at θ-temperature and composition.

Original languageEnglish
Pages (from-to)1623-1627
Number of pages5
Issue number3
Publication statusPublished - 1 May 2005
Externally publishedYes

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