Ames Laboratory and Department of Physics and Astronomy, Iowa State University , Ames, Iowa 50011, United States.
Langmuir. 2013 Sep 10;29(36):11420-30. doi: 10.1021/la401268s. Epub 2013 Aug 26.
Three representative polymers of increasing modulus, poly(d,l-lactic acid), PDLLA, poly(desaminotyrosyl-tyrosine ethyl ester carbonate), PDTEC, and the same polymer with iodinated DTE segments, PI2DTEC, were characterized by surface-pressure versus area (Π-A) isotherms and surface sensitive X-ray diffraction techniques. Films of 10-100 Å thickness were prepared for these studies by spreading dilute polymer solutions at air-water interfaces. The general properties of the isotherms and the Flory exponents, determined from the isotherms, vary in accordance with the increasing modulus of PDLLA, PDTEC, PI2DTEC, respectively. The analysis of in situ X-ray reflectivity and grazing incidence X-ray diffraction (GIXD) measurements from films at aqueous surfaces provides a morphological picture that is consistent with the modulus of the polymers, and to a large extent, with their packing in their dry-bulk state. Large absorption of X-rays by iodine enabled X-ray spectroscopic studies under near-total-reflection conditions to determine the iodine distribution in the PI2DTEC film and complement the structural model derived from reflectivity and GIXD. These structural studies lay the foundation for future studies of polymer-protein interactions at aqueous interfaces.
三种具有不同模量的代表性聚合物，聚（D，L-乳酸），PDLLA，聚（去氨基酪氨酸-酪氨酸乙酯碳酸酯），PDTEC，以及具有碘化 DTE 片段的相同聚合物，PI2DTEC，通过表面压与面积（Π-A）等温线和表面敏感 X 射线衍射技术进行了表征。这些研究使用在空气-水界面上展开稀聚合物溶液来制备 10-100 Å 厚度的薄膜。等温线的一般性质和 Flory 指数，由等温线确定，分别与 PDLLA、PDTEC、PI2DTEC 的模量增加一致。来自水相表面的原位 X 射线反射率和掠入射 X 射线衍射（GIXD）测量的分析提供了与聚合物模量一致的形态图像，在很大程度上与它们在干燥状态下的堆积方式一致。碘对 X 射线的大量吸收使 X 射线光谱研究能够在全反射条件下进行，以确定 PI2DTEC 薄膜中的碘分布，并补充从反射率和 GIXD 得出的结构模型。这些结构研究为未来在水相界面上进行聚合物-蛋白质相互作用的研究奠定了基础。
