The sol-gel transition in gelatin viewed by diffusing colloidal probes |
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| Affiliation: | 1. Sichuan Co-Innovation Center for New Energetic Materials, Southwest University of Science and Technology, Mianyang 621010, Sichuan, China;2. Sichuan Civil-military Integration Institute, Mianyang 621010, Sichuan, China;1. Electroceramics Group, Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz 13876-71557, Iran;2. Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran;1. Institute of Materials for Energy and Environment, State Key Laboratory of Bio-fibers and Eco-textiles, College of Materials Science and Engineering, Qingdao University, Qingdao, 266071, PR China;2. College of Electromechanical Engineering, Key Laboratory of Polymer Material Advanced Manufacturing''s Technology of Shandong Province, Qingdao University of Science and Technology, Qingdao, 266061, PR China;3. Institute of Physics & Optoelectronics Technology, Baoji University of Arts and Sciences, Baoji, 721016, PR China;4. State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400040, PR China;1. University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Polizu Street, 011061, Bucharest, Romania;2. National Institute for Research and Development in Environmental Protection, 294 Splaiul Independentei, 060031, Bucharest, Romania |
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| Abstract: | This paper reports a dynamic light scattering investigation of the sol-gel transition of gelatin solutions in the presence of latex spheres, which act as local probes for the viscoelasticity of the medium. The experimental procedure allows us to define a local gel time related to the size of the probes. In the sol state and in the gelling solutions, below the gel point, the dependence of the apparent diffusion coefficients of the spheres on correlation times, shows the existence of a fast local diffusion coefficient and of a slow long-term diffusion coefficient, related to viscosity. The behaviour of the fast diffusion coefficient during the course of gelation was quite unexpected, as it remained constant until the moment when the network was formed, when it suddenly started to increase. We propose a model for the diffusion of spherical particles in a viscoelastic medium (Voigt model) by using the Langevin equation. The experimental results are compared to the model. This investigation shows evidence for the coupling between the cooperative movements of the gel network and the local diffusion of the spheres. It illustrates the diffusion of particles through a disordered medium which leads to non-brownian, hypodiffusive regimes. |
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