Relaxations In Gelatin Hydrogels Probed By Dynamic Light Scattering

¹School of Physics, Shri Mata Vaishno Devi University, Katra 182320 (J&K), India

²Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa

Adv. Mater. Lett., 2016, 7 (2), pp 136-143

DOI: 10.5185/amlett.2016.6012

Publication Date (Web): Jan 04, 2016

Copyright © IAAM-VBRI Press

E-mail: jitendra.sharma@gmail.com

Abstract

The relaxation behavior of gelatin aqueous solutions has been investigated by time resolved dynamic light scattering (TRDLS) measurements at different temperatures spanning the entire sol to gel phase transition behavior of the system (i.e. from 5 min to 1440 min after a sudden quench from high temperature sol to low temperature gel state), when the chosen gelatin concentration in water was maintained at 5 % (w/v), well over the overlap threshold. The quantity of interest, structure factor S (q,τ), has been obtained from the experimentally measured autocorrelation function,  g₂(τ), allowing appropriate heterodyne contribution. The nonlinear regression analysis of the obtained scattering profiles (variation of structure factor vs. delay time) exhibited good fits to the function S(q,τ) ~A exp(-Dq²τ) + B exp(-(τ/τ_c)^β), up tosystem evolution time of 360 min, whereas the data obtained after 360 min showed appropriate fits to S(q,τ) ~A exp(-Dq²τ)+ Cτ^-α + B exp(-(τ/τ_c)^β). The temporal behavior of different fit parameters defining the transient structural network formed in the system has been quantified and analyzed under the purview of well-defined theories. Furthermore, the evolution of particle dynamics from fast to slow and then to almost frozen behavior has been explored through the continuous evaluation of ‘Gelation factor (κ)’ at different stages of system evolution times during the measurements.

Keywords

Time resolved dynamic light scattering, gelatin, sol-to-gel transitions, glass transitions,intensity correlation function.