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DSC Study on Cooperative Relaxation in 1,2-propanediol
Cai Gao*,Tie-jun Wang,Xiang-nong Liu,Guo-yan Zhou,Tse-chao Hua
Author NameAffiliationE-mail
Cai Gao* School of Mechanical and Automotive Engineering, Hefei University of Technology, Hefei 230009, China gao_cai@hotmail.com 
Tie-jun Wang School of Mechanical and Automotive Engineering, Hefei University of Technology, Hefei 230009, China  
Xiang-nong Liu School of Mechanical and Automotive Engineering, Hefei University of Technology, Hefei 230009, China  
Guo-yan Zhou Institute of Cryomedicine and Food Refrigeration, University of Shanghai for Science and Technology, Shanghai 200093, China  
Tse-chao Hua Institute of Cryomedicine and Food Refrigeration, University of Shanghai for Science and Technology, Shanghai 200093, China  
Abstract:
Cooling rate dependence of the cooperative relaxation in 1,2-propanediol was investigated in terms of the nonlinear Adam-Gibbs (AG) enthalpy relaxation theory using differential scanning calorimetry. The AG parameters were obtained using a curve-fitting method. The results indicated that the model parameters show strong dependence on the cooling rates. Those obtained at higher cooling rates are in good agreement with the published data. The fitting results were used to estimate the microscopic parameters of the cooperative rearranging region (CRR), in particular the size of the CRR (z*) and the configurational state available to it (W*). It was found that the W* recommended for polymers led to physically meaningless z* for 1,2-propanediol. Johari's method, which was based on the AG theory, yielded around 3 molecules in the CRR, but the W* was anomalistically higher than those of polymers. It is di±cult to reconcile the Adam-Gibbs' z* with the results obtained using Donth's formula. An argument is presented that a new physical meaning should be given to conventional Adam-Gibbs' z* for molecular H-bond liquids.
Key words:  Structure relaxation, Cooperative rearranging region, 1,2-propanediol, Di?erential scanning calorimetry
FundProject:
1,2-丙二醇协同松弛的DSC研究
高才*,王铁军,刘向农,周国燕,华泽钊
摘要:
利用差示扫描量热法(DSC)研究了1,2-丙二醇在不同降温速率下的协同松弛行为,以曲线拟合方法获得非线性Adam-Gibbs焓松弛参数.结果表明,模型参数强烈依赖于降温速率.在较高降温速率下获得的模型参数和用比热频谱及介电方法得到的结果很接近.利用DSC测得的比热容数据和拟合结果估算了1,2-丙二醇体系非线性AG理论的两个主要微观参数,即协同重排域(CRR)尺寸z*和对应的位形态数量W*.结果表明,如果采用聚合物玻璃推荐的W*,则会导致1,2-丙二醇在玻璃化温度处的CRR中的分子数小于1.而如果采用Johari的方法,则可得到玻璃化温度处的CRR中约有3个1,2-丙二醇分子,但随之产生的W*却异常的大.利用Donth的热力学温度波动公式估算得到的1,2-丙二醇在玻璃化温度处的CRR中的分子数为355,这和Johari方法得到结果难以统一.表明对于小分子氢键液体而言,非线性AG理论中z*的物理意义应重新审视.
关键词:  结构松弛,协同重排域,1,2-丙二醇,差示扫描量热法
DOI:10.1088/1674-0068/20/03/258-264
分类号: