A Sum Frequency Generation Vibrational Study of the Interference Effect in Poly(n-butyl methacrylate) Thin Films Sandwiched between Silica and Water
A Sum Frequency Generation Vibrational Study of the Interference Effect in Poly(n-butyl methacrylate) Thin Films Sandwiched between Silica and Water
复制标题
二氧化硅和水夹层聚甲基丙烯酸正丁酯薄膜干涉效应的和频产生振动研究
DOI：
10.1021/jp202416z
复制
发表时间：
2011-07-21
影响因子：
3.7
通讯作者：
Chen, Zhan
中科院分区：
文献类型：
--
作者：
Lu, Xiaolin;Clarke, Matthew L.;Chen, Zhan
在文献研究的基础上，采用薄膜模型对空气/二氧化硅/聚甲基丙烯酸正丁酯（PBMA）/水体系的厚度相关和频产生（SFG）光谱进行了解释.通过考虑PBMA层在SiO2/PBMA和PBMA/水界面的菲涅耳系数，得到了SiO2/PBMA和PBMA/水界面的SFG谱。在两个界面处的侧链甲基振动模式被发现具有相反的相位。这表明在两个界面处的侧链甲基采用不同的绝对取向。据信，考虑到疏水性甲基与亲水性二氧化硅表面和水之间的不利相互作用，两个界面处的甲基指向PBMA本体。取向分析表明，侧链甲基在两个界面倾斜更多的界面，而不是垂直于他们。应用薄膜模型的空气/PBMA/二氧化硅系统中，我们发现，从PBMA在空气中的表面信号占主导地位的SFG输出的相对较高的菲涅尔系数在这个表面上的掩埋PBMA/二氧化硅接口。
On the basis of the development in the literature, a thin film model was used to interpret the thickness-dependent sum frequency generation (SFG) spectra collected from the air/silica/poly(n-butyl methacrylate) (PBMA)/water system. By taking into account the Fresnel coefficients of the PBMA layers at the silica/PBMA and PBMA/water interfaces, the SFG spectra of the silica/PBMA and PBMA/water interfaces were obtained. The side chain methyl vibrational modes at the two interfaces were found to have opposite phases. This suggests that the side chain methyl groups at the two interfaces adopt different absolute orientations. It is believed that methyl groups at both interfaces point toward the PBMA bulk considering the unfavorable interactions between the hydrophobic methyl groups and hydrophilic silica surface and water. Orientation analysis indicates the side chain methyl groups at both interfaces tilt more toward the interfaces rather than be perpendicular to them. Applying the thin film model to the air/PBMA/silica system, we found that the surface signals from PBMA in air dominate the SFG output on account of the relatively higher Fresnel coefficients at this surface over those of the buried PBMA/silica interface.