冷却率相关的椭偏仪测量确定薄膜玻膜的动力学
Summary
在这里，我们提出了一个协议，用于冷却速率取决于椭圆光度法实验，可确定玻璃化转变温度 （Tg），平均动力学，脆性和超冷却的液体的膨胀系数和玻璃用于各种玻璃状材料。
Abstract
本报告旨在全面描述了利用椭偏仪的冷却速度依赖性T 克（CR-T G）实验的实验技术。这些测量是简单的高通量表征实验，由此可以判定玻璃化转变温度 （T g）中，平均动力学，脆性和超冷却的液体和玻璃状状态为各种玻璃材料的膨胀系数。此技术允许这些参数在一次实验中进行测量，而其它方法必须结合各种不同的技术来调查所有这些性能的。动态测量接近的 Tg是特别具有挑战性。冷却速度依赖性T 克测量在其上直接探测本体和表面弛豫动力学其他方法的优点是，它们是相对快速和简单的实验，不利用荧光团或其他复杂的前perimental技术。此外，这种技术探测技术相关的薄膜在温度和松弛时间（τα）制度有关的玻璃化转变（τα> 100秒）的平均动力学。的限制，使用椭圆偏光冷却速度依赖性T 克实验的是，它无法探测的弛豫时间相关的粘度测量（τα<< 1秒）。其他的冷却速度依赖的 Tg测量技术，但可以扩展CR-T 方法G更快的松弛时间。此外，该技术可以使用，只要该膜的完整性保持整个实验用于任何玻璃状系统。
Introduction
凯迪琼斯和Corey 1的开创性工作表明，超薄聚苯乙烯膜的玻璃化转变温度 （Tg）相对于所述体相值在厚度小于60nm的低减小。从那时起，许多实验研究2-11都支持所观察到的减少的 Tg是通过迁移率提高了的靠近这些膜的自由表面的层所引起的假设。然而，这些实验是一个单一的弛豫时间间接措施，因此，存在一个争论12-18集中于平均薄膜动力学和在空气/聚合物界面的动态之间有直接的关系。
要回答这个问题的争论，很多研究都直接测量自由表面（τ 面 ）的动态。纳米颗粒包埋，19,20纳米孔松弛，21和荧光22的研究表明，在空气/聚合物界面ħ作为级动力学订单比体的α松弛时间（τα）具有比τα的弱得多的温度依赖性更快。由于其弱的温度依赖性的，这些膜的表面 τ，薄聚苯乙烯膜的19-22和增强的动力学，23,24相交散装阿尔法松弛（τα）在一个单一的点T *，这是几度以上的 Tg，并在≈1秒的τα。的T *的存在可以解释为什么实验进行探测弛豫时间比*快看不到任何对的 Tg超薄聚苯乙烯薄膜的厚度依赖13-18最后，而增强的移动层，表明它具有直接测量厚度为4-8纳米，20-22有证据表明，在空气/聚合物界面的动态的传播长度比所述移动面Laye的厚度大得多河5,25,26
本报告旨在全面描述一个协议，利用椭偏仪的冷却速度依赖性T 克（CR-T G）的实验。的CR-T 克此前已用于描述超薄膜聚苯乙烯的平均动力。23,24,27,28此外，近来，使用该技术，以显示在超薄聚苯乙烯膜的平均动态之间有直接的关系和23的 CR-T 克测量优于其它类型的测量，如荧光，纳米粒子嵌入，纳米孔松弛，nanocalorimetry，介电谱，以及布里渊光散射的优点动力学在自由表面，研究的是，它们是相对快速和简单的实验不利用荧光团或其他复杂的实验技术。在椭圆偏振光谱法的最新进展允许使用这种技术能够有效地确定光普罗珀特超薄膜聚合物和其他类型的杂化材料具有优异的精度的独立实体。因此，该技术探测技术适用薄膜中的温度和时间制度有关的玻璃化转变（T≤ 的 Tg，τα≥100秒）的平均动力学。此外，这种技术将提供关于玻璃状的膨胀系数的信息和晚饭冷却液体状态以及该系统，然后可以用散装胶片数据相比较的脆弱性。最后，CR- 的 Tg实验可以使用，只要该膜的完整性保持整个实验用于任何玻璃状系统。
Protocol
Representative Results
Discussion
冷却速率依赖性T 克测量是高通量的表征实验可以确定该的 Tg，玻璃和超冷却的液体中，温度的平均动力学依赖的膨胀系数，和一个特定的玻璃状物质在脆弱一次实验。此外，与荧光，嵌入，或纳米孔松弛实验，CR-T 克实验是相对快速和简单的，因为他们不使用荧光团或其他复杂的实验技术。由于椭圆偏振的敏感性，这种方法可用于厚度薄至几纳米，厚至几微米的膜，只要…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
笔者想感谢詹姆斯·福雷斯特在这种技术最初的想法帮助。26这项工作是由美国宾夕法尼亚大学的资金支持，由美国国家科学基金会的MRSEC计划下奖项是部分支持没有。 DMR-11- 20901在宾夕法尼亚大学。
Materials
| Toluene | Sigma Aldrich | 179418-1L | This can be purchased from any chemical company. |
| Atactic Polystyrene | Polymer Source Inc. | P-4092-S | This can be purchased from any chemical company. |
| THMS 600 temperature stage | Linkam | THMS 600 | any temperature stage that can be fit to an ellipsometer could be used. |
| M2000V Spectroscopic Ellipsometer | J.A. Woollam | M200V | This procedure should be applicable for any spectroscopic ellipsometer. |
| Spin Coater | Laurell Technologies | WS-650-23B | This Procedure is possible with any spin coater |
| Sample vials | Fisher Scientific | 02-912-379 | Any sample vials will do |
| Silicon wafers | Virginia semi conductors | 325S1410694D |
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