title: Internal structures of agar-gelatin co-hydrogels by light scattering, small-angle neutron scattering and rheology.
abstract: Internal structures of agar-gelatin co-hydrogels were investigated as a function of their volumetric mixing ratio, [Formula: see text] , 1.0 and 2.0 using dynamic light scattering (DLS), small-angle neutron scattering (SANS) and rheology. The degree of non-ergodicity ( X = 0.2 ± 0.02) , which was extracted as a heterodyne contribution from the measured dynamic structure factor data remained less than that of homogeneous solutions where ergodicity is expected (X = 10. The static structure factor, I(q) , results obtained from SANS were interpreted in the Guinier regime (low-q , which implied the existence of ≈ 250 nm long rod-like structures (double-helix bundles), and the power law (intermediate-q regions) yielded I (q) ~ q(−α) with α = 2.3 , 1.8 and 1.6 for r = 0.5 , 1.0 and 2.0. This is indicative of the presence of Gaussian chains at low r , while at r = 2 there was a propensity of rod-shaped structures. The gel strength and transition temperatures measured from frequency sweep and temperature ramp studies were suggestive of the presence of a stronger association between the two biopolymer networks at higher r . The results indicate that the internal structures of agar-gelatin co-hydrogels were highly dependent on the volumetric mixing ratio.
authors.affiliation: Polymer and Biophysics Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi, India. santinathsingh@yahoo.com
authors.forename: S
authors.initials: S
authors.lastname: Santinath Singh
authors.forename: V K
authors.initials: VK
authors.lastname: Aswal
authors.forename: H B
authors.initials: HB
authors.lastname: Bohidar
mesh_terms: D000362:Agar / Q000737:chemistry*; D000465:Algorithms; D005780:Gelatin / Q000737:chemistry*; D005782:Gels / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry*; D008027:Light; D033363:Neutron Diffraction / Q000379:methods*; D012212:Rheology; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D012996:Solutions; D013696:Temperature
chemical_list: D005782:Gels; D020100:Hydrogels; D012996:Solutions; D005780:Gelatin; D000362:Agar