Enthalpy recovery for a single polystyrene ultrathin film of 20 nm thickness is studied using Flash DSC over an extended time and temperature range. Results are compared to a bulk sample of the same polystyrene using a similar experimental protocol and analysis procedure in an effort to determine the effects of nanoconfinement. Examined is the cooling rate dependence of the glass transition temperature (T_g) of unaged films which informs the initial fictive temperature (T_fo) and thus the jump size (T_fo - T_a) for a given aging temperature (T_a). Isothermal enthalpy recovery is investigated as a function of both T_a for various cooling rates and as a function of jump size at constant T_a. The apparent activation energies at T_g and along the glassy line are determined and compared, as is the enthalpy recovery aging rate. Although the apparent activation energy along the glass line is the same within experimental error as the bulk, the aging rate is found to be slightly faster in the ultrathin film. Increasing the cooling rate prior to aging increases the aging rate. The results are discussed in the context of the two competing factors which influence the aging rate, namely, the driving force and the molecular mobility. The driving force for aging is dictated by the jump size or cooling rate, i.e., the value of T_fo - T_a. The mobility, on the other hand, is dictated by the relaxation time at the aging temperature, which increases during aging from the value on the initial glass line to that at equilibrium. The initial mobility in the glassy state is dictated by the jump size, being related to T_fo - T_a and the temperature dependence of the relaxation time along the glass line, whereas the mobility at equilibrium is dictated by T_a, T_g, and the temperature dependence and breadth of the equilibrium relaxation time.

使用Flash DSC在扩展的时间和温度范围内研究了20 nm厚的单个聚苯乙烯超薄膜的焓回收率。使用相似的实验方案和分析程序，将结果与相同聚苯乙烯的大量样品进行比较，以努力确定纳米约束作用。检查是玻璃化转变温度（T的冷却速度依存性_克未老化膜），其通知初始假想温度（T _FO），因此跳跃大小（T _FO - T的_一个），用于在给定时效温度（T_一）。在不同的冷却速率下，等温焓的恢复与T _a的关系以及在恒定T处的跃迁尺寸的关系都得到了研究_一个。确定并比较在T _g和沿着玻璃线的表观活化能，以及焓回收老化率。尽管在实验误差范围内沿玻璃线的表观活化能与体积相同，但发现超薄膜的老化速率稍快。在老化之前增加冷却速率会增加老化速率。在影响老化速率的两个竞争因素的背景下讨论了结果，即驱动力和分子迁移率。老化的驱动力由跳跃大小或冷却速率（即T _fo -T _a的值）决定。另一方面，迁移率由时效温度下的弛豫时间决定，其在时效过程中从初始玻璃线上的值增加到平衡时的值。在玻璃态下的初始迁移率是由跳跃大小支配，被相关至T _FO - T的_一个和沿玻璃线的弛豫时间对温度的依赖性，而在平衡状态下的迁移率用T决定_一个，T_克，和温度依赖性和平衡弛豫时间的宽度。