Yoon Heedong, McKenna Gregory B
Department of Chemical Engineering, Whitacre College of Engineering, Texas Tech University, Lubbock, TX 79409-3121, USA.
Sci Adv. 2018 Dec 21;4(12):eaau5423. doi: 10.1126/sciadv.aau5423. eCollection 2018 Dec.
A major challenge to understanding glass-forming materials is obtaining equilibrium data far below the laboratory glass transition temperature . The challenge arises because it takes geologic aging times to achieve the equilibrium glassy state when temperatures are well below . Here, we finesse this problem through measurements on an ultrastable amorphous Teflon with fictive temperature near to its Kauzmann temperature . In the window between and , the material has a lower molecular mobility than the equilibrium state because of its low specific volume and enthalpy. Our measurements show that the determined scaled relaxation times deviate strongly from the classical expectation of divergence of time scales at a finite temperature. The results challenge the view of an ideal glass transition at or near to .
理解玻璃形成材料面临的一个主要挑战是获取远低于实验室玻璃化转变温度的平衡数据。之所以会出现这一挑战，是因为当温度远低于该温度时，需要地质年代的老化时间才能达到平衡玻璃态。在此，我们通过对一种超稳定无定形聚四氟乙烯进行测量来巧妙解决这个问题，该聚四氟乙烯的虚构温度接近其考兹曼温度。在该温度区间内，由于其低比容和低焓，材料的分子迁移率低于平衡态。我们的测量结果表明，所确定的标度弛豫时间与有限温度下时间尺度发散的经典预期有很大偏差。这些结果对在该温度或接近该温度时存在理想玻璃转变的观点提出了挑战。
