Aging phenomena and non-equilibrium relaxation in polymer glass

聚合物玻璃的老化现象和非平衡弛豫

基本信息

批准号：
16340122
负责人：
FUKAO Koji
金额：
$ 10.5万
依托单位：
Kyoto Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

1) The aging dynamics in thin films of poly (methyl methacrylate) (PMMA) have been investigated through dielectric measurements for different types of aging processes. The dielectric constant was found to decrease with increasing aging time at an aging temperature in many cases. In the constant-rate mode including a temporary stop at a temperature Ta, the memory of the aging at Ta was found to be kept and then to be recalled during the subsequent heating process. In the negative-temperature cycling process, a strong rejuvenation effect has been observed after a large temperature shift. Furthermore, a full memory effect has also been observed for the temperature shift. This suggests that the aging at T1 is totally independent of that at T2 for ΔT<-20 K.2) The aging behavior is investigated for thin films of atactic polystyrene through measurements of complex electric capacitance. During isothermal aging process the real part of the electric capacitance increases with aging time, while t … More he imaginary part decreases with aging time. This result suggests that the aging time dependence of the real and imaginary parts are mainly associated with change in thickness and dielectric permittivity, respectively. In thin films, the thickness depends on thermal history of aging even above the glass transition. Memory and 'rejuvenation' effects are also observed in the thin films.3) The aging behavior of polymer glass, poly(methyl methacrylate), has been investigated through the measurement of ac dielectric susceptibility at a fixed frequency after a temperature shift ΔT (-20 K) between two temperatures, T1 and T2. A crossover from cumulative aging to non-cumulative aging could be observed with increasing ΔT using a twin temperature (T-) shift measurement. Based on a growth law of a dynamical coherent length given by activated dynamics, we obtained a unique coherent length for positive and negative T-shifts. The possibility of the existence of temperature chaos in polymer glasses is discussed. Less

1) 通过对不同类型的老化过程进行介电测量，研究了聚甲基丙烯酸甲酯 (PMMA) 薄膜的老化动力学，发现在许多情况下，介电常数随着老化温度的增加而降低。在包括在温度Ta下暂时停止的恒定速率模式中，发现Ta处的老化记忆被保留，然后在随后的加热过程中被调用，具有很强的回春效应。观察后此外，还观察到温度变化的完全记忆效应，这表明当 ΔT<-20 K 时，T1 处的老化完全独立于 T2 处的老化。2）研究了薄层的老化行为。通过测量复电容来测量无规聚苯乙烯薄膜，在等温老化过程中，电容的实部随着老化时间的延长而增加，而虚部则随着老化时间的延长而减少。实部和虚部的依赖性主要分别与厚度和介电常数的变化有关，在薄膜中，厚度取决于甚至在玻璃化转变之上的记忆和“再生”效应。 3) 通过测量两个温度之间的温度变化 ΔT (-20 K) 后固定频率下的交流介电敏感性，研究了聚合物玻璃、聚甲基丙烯酸甲酯的老化行为， T1 和 T2。使用双温度 (T-) 位移测量可以观察到从累积老化到非累积老化的交叉。基于激活动力学给出的动态相干长度的增长定律，我们获得了一个独特的结果。正负 T 位移的相干长度讨论较少。