Effect of temperature on alpha olefin sulfonate induced softening of gelatin hydrogels.
Dynamic light scattering (DLS) and oscillatory rheology experiments were performed to study temperature dependence (T=10-25 degrees C) of the interactions in hydrogels of gelatin with AOS (alpha olefin sulfonate, anionic surfactant) for surfactant concentrations in the range 25-100 mM, chosen larger than cmc (approximately 8mM). The network mesh size (xi) values deduced from fastmode diffusivity (D(f)) data obtained from dynamic structure factor measurements, S(q, t) approximately exp(-D(f)q(2)t) (for t<or=1 ms and q being the scattering wave vector), of micelle-bound gelatin gels was analyzed within the framework of Flory-Rhener theory of cross-linking, which revealed a temperature dependence, xi approximately (0.5-chi)(1/5)exp(-DeltaG(Total)/RT) where chi is the Flory-Huggins interaction parameter, the free-energy of the gel-surfactant complex is DeltaG(Total) and R is universal gas constant. The low-frequency isochronal storage, G' and loss, G'' modulii revealed a transition from the rigid to a softened gel state occurring at surfactant concentration close to 55 mM, independent of temperature. The free-energy of interaction between gel and surfactant deduced from Arrhenius plots obtained from temperature dependent rheology, and light scattering data support this observation.
Abed
Mazin Ahmad
MA
School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
Bohidar
H B
HB
D000475:Alkenes / Q000737:chemistry*; D005780:Gelatin / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D012212:Rheology; D013451:Sulfonic Acids / Q000737:chemistry*
D000475:Alkenes; D020100:Hydrogels; D013451:Sulfonic Acids; D005780:Gelatin