Thermodynamics of conformational transition and chain association of ι-carrageenan in aqueous solution: Calorimetric and chirooptical data

✍ Scribed by B. Denef; A. Gamini; F. Delben; S. Paoletti; H. Reynaers; K. Vanneste

• Publisher: Wiley (John Wiley & Sons)
• Year: 1998
• Tongue: English
• Weight: 180 KB
• Volume: 45
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/(sici)1097-0282(199802)45:2<105::aid-bip2>3.0.co;2-w

✦ Synopsis

Isothermal microcalorimetry, differential scanning calorimetry (DSC), and chirooptical data obtained for i-carrageenan in NaCl, LiCl, and NaI aqueous solutions are presented. The experiments have been performed as a function of concentration both for the polymer and for the simple salt as a cosolute. The experimental findings consistently show the occurrence of a salt-induced disorder-to-order transition. From microcalorimetric experiments the exothermic enthalpy of transition DH tr is obtained as the difference between the theoretical, purely electrostatic DH el enthalpy change and the actual mixing enthalpy DH mix , measured when a icarrageenan salt-free solution at constant polymer concentration is mixed with a 1:1 electrolyte solution of variable concentration. In the case of added NaCl, the absolute values of enthalpy changes ÉDH tr É are in good agreement with those obtained for the opposite process, at comparable polymer and salt concentrations, from DSC melting curves. The microcalorimetric results show that the negative maximum value of DH tr corresponding to the interaction of Li / counter-* On leave from the