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首页> 外文期刊>The Journal of Chemical Physics >Non-exponential relaxation, fictive temperatures, and dispersive kinetics in the liquid-glass-liquid transition range of acetaminophen, sulfathiazole, and their mixtures
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Non-exponential relaxation, fictive temperatures, and dispersive kinetics in the liquid-glass-liquid transition range of acetaminophen, sulfathiazole, and their mixtures

机译：对乙酰氨基酚，磺胺噻唑及其混合物的液-玻璃-液转变范围内的非指数弛豫，虚拟温度和分散动力学

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To investigate the effects of added molecular heterogeneity on the hysteretic features of liquid-glass-liquid transition, we studied acetaminophen, sulfathiazole, and three of their mixtures by calorimetry, and determined the T-g and the fictive temperature, T-f, from changes in the enthalpy and entropy on the cooling and heating paths, as well as the non-exponential parameter, beta(cal). We find that, (i) T-f for cooling is within 1-3 K of T-f for heating and both are close to T-g, (ii) the closed loop entropy change in the liquid-glass-liquid range is negligibly small, (iii) T-g and T-f increase on increasing sulfathiazole in the mixture, (iv) beta(cal) first slightly increases when the second component is added and then decreases, and (v) ageing causes deviations from a non-exponential, nonlinear behavior of the glass. In terms of fluctuations in a potential energy landscape, adding a solute heterogeneity would shift the state point to another part of the landscape with a different distribution of barrier heights and a different number of minima accessible to the state point. Part of the change in beta(cal) is attributed to hydrogen-bond formation between the two components. Ageing changes the relaxation times distribution, more at short relaxation times than at long relaxation times, and multiplicity of relaxation modes implied by beta(cal) < 1 indicates that each mode contributing to the enthalpy has its own T-g or T-f. beta(cal) differs from beta(age) determined from isothermal ageing, and the distribution parameter of a-relaxation times would differ from both beta(cal) and beta(age). (C) 2014 AIP Publishing LLC.
机译：为了研究增加的分子异质性对液-玻璃-液转变的滞后特性的影响，我们通过量热法研究了对乙酰氨基酚，磺胺噻唑及其三种混合物，并根据焓变确定了Tg和虚拟温度Tf。以及冷却和加热路径上的熵以及非指数参数beta（cal）。我们发现，（i）冷却的Tf在加热的Tf的1-3 K范围内，并且都接近Tg，（ii）液-玻璃-液体范围内的闭环熵变化很小，（iii） Tg和Tf随着混合物中硫代噻唑的增加而增加，（iv）当添加第二种组分时，β（cal）首先略微增加，然后降低，并且（v）老化会导致偏离玻璃的非指数非线性行为。就潜在能量格局的波动而言，增加溶质异质性会使状态点移动到格局的另一部分，势垒高度的分布不同且状态点可访问的最小值数量不同。 β（cal）的部分变化归因于两个组分之间的氢键形成。老化改变了弛豫时间分布，在短弛豫时间比在长弛豫时间更多，并且由beta（cal）<1暗示的弛豫模式的多样性表明，贡献焓的每个模式都有自己的T-g或T-f。 beta（cal）与等温老化确定的beta（age）不同，并且a松弛时间的分布参数与beta（cal）和beta（age）都不同。 （C）2014 AIP Publishing LLC。

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