title: Flory temperature and upper critical solution temperature of gelatin solutions.
abstract: The Flory temperatures (theta) 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 degrees C for salt concentrations 0.1, 0.075, 0.05, 0.025, and 0 M (NaCl), respectively. Estimated persistence length (l(p)) 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 l(p) = 9(R(h))(2)/(5L(m)), where L(m) is the contour length and R(h) is the hydrodynamic radius. It was found that l(p) approximately 2.2 +/- 0.2 nm at room temperature (20 degrees C), invariant of salt concentration. The Flory expansion factor (alpha= R(h)(T)/R(h)(theta) = 1.5+/-0.2) was found to be almost constant. theta-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 theta-temperature and composition.
authors.affiliation: School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067, India.
authors.forename: Amarnath
authors.initials: A
authors.lastname: Gupta
authors.forename: B
authors.initials: B
authors.lastname: Mohanty
authors.forename: H B
authors.initials: HB
authors.lastname: Bohidar
mesh_terms: D005780:Gelatin / Q000032:analysis / Q000737:chemistry*; D009391:Nephelometry and Turbidimetry; D009994:Osmolar Concentration; D012996:Solutions; D013696:Temperature
chemical_list: D012996:Solutions; D005780:Gelatin