Measuring the surface dynamics of glassy polymers
Measuring the surface dynamics of glassy polymers
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DOI：
10.1126/science.1151205
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发表时间：
2008-02-01
期刊：
影响因子：
56.9
通讯作者：
Forrest, J. A.
中科院分区：
文献类型：
--
作者：
Fakhraai, Z.;Forrest, J. A.
冷却到低于玻璃化转变温度的聚合物链段的运动显著减慢;在充分冷却的情况下，链段运动变得完全停止。有争议的是，是否在自由表面附近的链段，或在薄膜中，以同样的方式作为散装材料的影响。通过部分嵌入然后去除金纳米球，我们在聚苯乙烯表面上产生了高度表面覆盖的良好定义的纳米变形;为了探测表面动力学，我们测量了这些表面变形随温度从277到369开尔文的时间依赖性弛豫。在所有温度下观察到表面弛豫，提供了强有力的直接证据，增强表面流动性相对于散装。随着温度降低到低于体相玻璃化转变温度，从体相a弛豫的偏离变得更加明显。的弛豫时间的温度依赖性是弱得多的比大体积的松弛的聚苯乙烯，该过程表现出没有明显的温度依赖性之间的277和307开尔文。
The motion of polymer chain segments cooled below the glass transition temperature slows markedly; with sufficient cooling, segmental motion becomes completely arrested. There is debate as to whether the chain segments near the free surface, or in thin films, are affected in the same way as the bulk material. By partially embedding and then removing gold nanospheres, we produced a high surface coverage of well- defined nanodeformations on a polystyrene surface; to probe the surface dynamics, we measured the time- dependent relaxation of these surface deformations as a function of temperature from 277 to 369 kelvin. Surface relaxation was observed at all temperatures, providing strong direct evidence for enhanced surface mobility relative to the bulk. The deviation from bulk a relaxation became more pronounced as the temperature was decreased below the bulk glass transition temperature. The temperature dependence of the relaxation time was much weaker than that of the bulk a relaxation of polystyrene, and the process exhibited no discernible temperature dependence between 277 and 307 kelvin.