Frieberg Bradley, Kim Jenny, Narayanan Suresh, Green Peter F
Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States.
ACS Macro Lett. 2013 May 21;2(5):388-392. doi: 10.1021/mz400104p. Epub 2013 Apr 22.
In thin film A/B polymer/polymer mixtures, the formation of a layer at the free surface, with average composition that differs from the bulk, due to the preferential segregation of the lower cohesive energy density component, is well understood. While much is also understood about this surface layer formation and growth to date, virtually nothing is known about the surface dynamics of the chains in such mixtures. Questions about the surface chain dynamics in relation to the bulk have remained unanswered. With the use of X-ray photon correlation spectroscopy (XPCS) we show that the dynamics of poly(vinyl methyl ether) (PVME) chains at the free surface of polystyrene (PS)/PVME thin film mixtures can be orders of magnitude larger than the PVME chains in the bulk. These dynamics manifest from differences between the local compositions of the blend at the free surface and the bulk, as well as film thickness constraints.
在薄膜A/B聚合物/聚合物混合物中，由于内聚能密度较低的组分优先偏析，在自由表面形成了一层平均组成与本体不同的层，这一点已得到充分理解。虽然到目前为止对这种表面层的形成和生长也有很多了解，但对于此类混合物中链的表面动力学几乎一无所知。关于表面链动力学与本体的关系问题仍未得到解答。通过使用X射线光子相关光谱法（XPCS），我们表明，在聚苯乙烯（PS）/聚（乙烯基甲基醚）（PVME）薄膜混合物的自由表面，PVME链的动力学可能比本体中的PVME链大几个数量级。这些动力学表现为自由表面和本体处共混物局部组成的差异以及薄膜厚度的限制。
