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《Acta Physico-Chimica Sinica》 2007-02
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Glass Transition and Structure Relaxation of 1,2-Propanediol Aqueous Solutions

GAO Cai1, * WANG Tie-Jun1 ZHOU Guo-Yan2 HUA Ze-Zhao2 (1Key Laboratory of Farm Product and Biochemical Engineering, Ministry of Education of China, College of Mechanical and Automotive Engineering, Hefei University of Technology, Hefei 230009, P. R. China; 2 Institute of Cryomedicine and Food Refrigeration, Shanghai University for Science and Technology, Shanghai 200093, P. R. China)  
In order to examine the effects of water contents on glass transition and structure relaxation parameters of 1, 2-propanediol (PD) aqueous glasses, apparent specific heat capacity during glass transition processes of five PD aqueous solutions with high concentrations (60%, 70%, 80%, 90%, and 100%, w) were determined using the differential scanning calorimetry (DSC). Five cooling rates (1, 2, 5, 10, 20 K·min-1) and one heating rate (10 K·min-1) were used to obtain the glass transition and structure relaxation parameters. Water seemed to be no obvious plasticization effect on 1, 2-propanediol (compared to some "pure hydroxyl group" linear polyalcohol) since the glass transition temperatures of the aqueous solutions were only slightly decreased with the increasing of water content. The structure relaxation activation energies were found to decrease as the water content increased. A comparison of thermodynamic fragility(ΔCp) and dynamic fragility (Angell′s fragility) was present and no similar trend was found with the changing of the component, since the former increased first and decreased last. The calculating results of dynamic fragility indicated that 1, 2-propanediol aqueous solutions behaved as though they were "stronger" than the pure solute. The sizes of cooperative rearrangement region (CRR) discussed in the term of glass transition characteristic length were determined using Donth's thermodynamic temperature fluctuant method. It was found that the sizes of CRR decreased as the water content increasing in 1,2-propanediol aqueous solutions.
【Fund】: 国家自然科学基金(50376040、50206013);; 合肥工业大学青年学术骨干启动资金资助项目
【CateGory Index】: O621.21
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