Composition‐dependent glass transition temperature in mixtures: Evaluation of configurational entropy models
Composition‐dependent glass transition temperature in mixtures: Evaluation of configurational entropy models
复制标题
混合物中与成分相关的玻璃化转变温度：构型熵模型的评估
DOI：
10.1002/pen.26018
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发表时间：
2022
影响因子：
3.2
通讯作者：
Simon, Sindee L.
中科院分区：
文献类型：
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作者：
Lopez, Evelyn;Koh, Yung P.;Zapata‐Hincapie, John A.;Simon, Sindee L.
在混合物中的玻璃化转变温度（Tg）的组成依赖性仍然是一个重要的未解决的问题。在这里，它是使用三个模型系统：一系列的低聚和聚合的氰尿酸酯，低聚和聚合的α-甲基苯乙烯的共混物，以及伊曲康唑和泊沙康唑的分子混合物。我们评估了几种基于熵的模型，以确定理论Tgas作为分子组成的函数，并将结果与实验数据进行比较。构型熵在Tg不变的假设得到了验证，其中构型熵的变化被假设为由ΔCpdlnT的积分给出，其中Δ Cp是Tg时热容随温度的变化。我们发现，虽然在液态和玻璃态下的温度依赖性热容几乎与所研究的几个系统的组成无关（即，它们几乎是理想的混合物），Tgis的组成依赖性不能通过简单地将组分的质量加权构型熵的变化从纯态的Tgis增加到共混物的Tgis来很好地描述。这意味着构型熵在T上不是不变的，或者它不能从ΔCpdlnT的积分中获得。
The composition dependence of the glass transition temperature (Tg) in mixtures remains an important unsolved problem. Here, it is revisited using three model systems: a series of oligomeric and polymeric cyanurates, blends of oligomeric and polymeric α‐methyl styrene, and molecular mixtures of itraconazole and posaconazole. We evaluate several entropy‐based models to determine the theoreticalTgas a function of molecular composition and compare the results against the experimental data. The assumption that the configurational entropy is invariant at theTgis tested, where the change in configurational entropy is assumed to be given by the integral of ΔCpdlnT, where ΔCpis the temperature‐dependent change in the heat capacity atTg. We find that, although the temperature‐dependent heat capacities in both liquid and glassy states are nearly independent of composition for several of the systems studied (i.e., they are nearly ideal mixtures), the composition dependence ofTgis not well described by simply adding the changes in the mass‐weighted configurational entropy of the components on going from theTgin the pure state to that of the blend. The implication is that either configurational entropy is not invariant atTgor that it cannot be obtained from the integral of ΔCpdlnT.