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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Molecular Orientations in Azopolymer Holographic Diffraction Gratings as Studied by Raman Confocal Microspectroscopy
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Molecular Orientations in Azopolymer Holographic Diffraction Gratings as Studied by Raman Confocal Microspectroscopy

机译：拉曼共聚焦显微技术研究的偶氮聚合物全息衍射光栅中的分子取向

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Optically isotropic films of an amorphous copolymer containing azobenzene moieties (pDR1M-co-MMA) were irradiated by interfering two circularly contrarotating polarized laser beams and permanent holographic diffraction gratings were prepared. These involve the formation of both birefringence and surface relief gratings. Using the Raman confocal microspectrometry, we have recorded various resonance enhanced polarized Raman spectra from the surface profile in order to get new insight into the orientational and angular distributions of the chromophore species. Different theoretical equations of the Raman Scattering intensities, including a treatment taking into account the effect of the high numerical aperture objective, were thus derived. Calculations and simulations of these equations allowed us to extract the second and fourth coefficients of the chomophore orientation function in various regions of the surface grating and to obtain the corresponding information entropy normalized distribution functions. From the various shapes of the distribution functions we discuss the photoinduced effects and suggest that mass-transport effects must be also effective. Finally, in agreement with the modulated relative Raman intensities and four distinct distribution functions observed along the surface grating, we conclude that the orientational orders are primarily generated by an angular dependent photoselection process, which acts as an initializing force in the establishment of the various molecular organized domains. Such molecular organizations could occur in the viscoelastic state of the polymer and be responsible for an amplification of the light induced anisotropic effects in some regions (at the bottoms) and for a significant perturbation of the orientations in other regions (at the tops of the surface profile). In agreement with previous studies about the mechanisms of grating formation, these results are consistent with a model involving the existence of large pressure gradients due to a viscoelastic flow of the polymer.
机译：通过干涉两个圆反向旋转的偏振激光束，照射含有偶氮苯部分的无定形共聚物的光学各向同性膜（pDR1M-co-MMA），并制备了永久性全息衍射光栅。这些涉及双折射和表面起伏光栅的形成。使用拉曼共聚焦显微技术，我们从表面轮廓记录了各种共振增强极化拉曼光谱，以便对发色团物种的方向和角度分布有新的认识。因此得出了拉曼散射强度的不同理论方程式，包括考虑了高数值孔径物镜效果的处理方法。这些方程的计算和模拟使我们能够提取表面光栅各个区域中的荧光团取向函数的第二和第四系数，并获得相应的信息熵归一化分布函数。从分布函数的各种形状中，我们讨论了光诱导效应，并提出了传质效应也必须是有效的。最后，与调制的相对拉曼强度和沿表面光栅观察到的四个不同的分布函数相一致，我们得出结论，取向阶次主要是由与角度有关的光选择过程产生的，该过程在各种分子的建立中充当初始化力有组织的域名。这种分子组织可能以聚合物的粘弹性状态发生，并导致某些区域（底部）中光诱导的各向异性效应的放大，并导致其他区域（表面顶部）中取向的显着扰动。个人资料）。与关于光栅形成机理的先前研究一致，这些结果与涉及由于聚合物的粘弹性流动而存在大的压力梯度的模型相一致。

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