Fragility is a Key Parameter in Determining the Magnitude of Tg-Confinement Effects in Polymer Films
Fragility is a Key Parameter in Determining the Magnitude of Tg-Confinement Effects in Polymer Films
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DOI：
10.1021/ma401017n
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发表时间：
2013-07
期刊：
影响因子：
5.5
通讯作者：
C. M. Evans;Hui Deng;W. Jager;J. Torkelson
中科院分区：
文献类型：
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作者：
C. M. Evans;Hui Deng;W. Jager;J. Torkelson
使用基于荧光的测量，在七个聚合物系统的单层膜支持在硅衬底上的玻璃化转变温度（Tg）上的限制的效果进行了研究，所有选择，使他们没有实质性的基板相互作用。聚（氯乙烯）表现出最陡峭的降低Tg与降低膜厚度。在聚砜中观察到Tg降低的最大幅度，其中24 nm厚的膜报告Tg相对于本体降低53 °C。还选择了在13-14 nm的厚度下不表现出限制效应的系统。差示扫描量热法被用来确定动态脆弱性，以测试的假设，即脆弱性是一个关键变量的Tg约束效应的大小。在本研究中的系统显示了一个一对一的相关性更高的脆性和更大幅度的玻璃化转变温度降低与降低膜厚度。特别是，Tg/Tg，散装表现出普遍的性质作为一个功能…
Using fluorescence-based measurements, the effect of confinement on the glass transition temperature (Tg) was investigated in seven polymer systems of single-layer films supported on silicon substrates, all chosen such that they do not have substantial substrate interactions. Poly(vinyl chloride) exhibited the steepest reduction in Tg with decreasing film thickness. The largest magnitude of Tg reduction was observed in polysulfone where a 24-nm-thick film reported a Tg reduced by 53 °C relative to bulk. A system was also selected which exhibited no confinement effect at a thickness of 13–14 nm. Differential scanning calorimetry was used to determine dynamic fragilities in order to test the hypothesis that fragility is a key variable governing the magnitude of Tg-confinement effects. The systems in the present study show a one-to-one correlation between higher fragility and larger magnitudes of Tg reduction with decreasing film thickness. In particular, Tg/Tg,bulk exhibits a universal nature as a function ...