Madkour Sherif, Szymoniak Paulina, Hertwig Andreas, Heidari Mojdeh, von Klitzing Regine, Napolitano Simone, Sferrazza Michele, Schönhals Andreas
Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany.
Fachbereich für Physik, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany.
ACS Macro Lett. 2017 Oct 17;6(10):1156-1161. doi: 10.1021/acsmacrolett.7b00625. Epub 2017 Oct 2.
The discussions on the nanoconfinement effect on the glass transition and glassy dynamics phenomena have yielded many open questions. Here, the thickness dependence of the thermal glass transition temperature of thin films of a PVME/PS blend is investigated by ellipsometry. Its thickness dependence was compared to that of the dynamic glass transition (measured by specific heat spectroscopy) and the deduced Vogel temperature (). While and showed a monotonous increase, with decreasing film thickness, the dynamic glass transition temperature () measured at a finite frequency showed a nonmonotonous dependence that peaks at 30 nm. This was discussed by assuming different cooperativity length scales at these temperatures, which have different sensitivities to composition and thickness. This nonmonotonous thickness dependence of disappears for frequencies characteristic for . Further analysis of the fragility parameter showed a change in the glassy dynamics from strong to fragile, with decreasing film thickness.
关于纳米限域效应在玻璃化转变和玻璃态动力学现象方面的讨论产生了许多未解决的问题。在此，通过椭偏仪研究了聚甲基乙烯基醚/聚苯乙烯（PVME/PS）共混物薄膜的热玻璃化转变温度的厚度依赖性。将其厚度依赖性与动态玻璃化转变（通过比热光谱测量）和推导的Vogel温度（）进行了比较。虽然 和 随着薄膜厚度减小呈现单调增加，但在有限频率下测量的动态玻璃化转变温度（）表现出非单调依赖性，在30 nm处出现峰值。通过假设在这些温度下不同的协同长度尺度来对此进行讨论，这些尺度对组成和厚度具有不同的敏感性。对于 的特征频率，这种 的非单调厚度依赖性消失。对脆性参数的进一步分析表明，随着薄膜厚度减小，玻璃态动力学从强变脆。
