Microscopic structure of gelatin coacervates

Microscopic structure of simple coacervates of gelatin having concentration ∼130 g/l were studied at 25 °C by atomic force microscopy (AFM), rheology, small angle neutron scattering (SANS), UV absorption and circular dichroism (CD) techniques. The behavior of viscoelastic exponents Δ′ and Δ″ of storage and loss modulii (G′(ω) ∼ ωΔ′, G″(ω) ∼ ωΔ″) revealed that, Δ′ = 0.25 ± 0.01 and Δ″ = 0.78 ± 0.1 for coacervates. The mass fractal dimension 'df' for coacervate was found to be 2.27, which attributed a compact heterogeneous network structure to the coacervates. This is supported by AFM pictures. The CD and UV absorption data indicated presence of helical structures inside the coacervates phase. SANS results showed the existence of a single length scale associated with this system identified as gelatin persistence length, ζ = 27 ± 2 Å. These studies indicate that the coacervate phase is a low dimensional dense heterogeneous material comprised of strongly interconnected triple helices which imparts a large storage modulus to this material.