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Abstract：
Polyethylene terephthalate (PET) films are the subject of intensive research because of great interest in using them in applications, especially in medicine. From an optical point of view, PET films with a low degree of stretching can be considered uniaxial materials, for which the determination of the linear birefringence and its dispersion is very important. Two methods were applied here for the estimation of these parameters: the ellipsometric method and the channeled spectra method. The ellipsometric method uses monochromatic radiation; therefore, the linear birefringence of the PET films is determined for a given value of the radiation wavelength. The channeled spectra method allows for the estimation of the linear birefringence and its dispersion for a large range of wavelengths in the visible spectrum. A decrease in both parameters with the increase in the wavelength was recorded. To evidence the microstructure of PET films and the conformational changes induced by elongation and to evaluate the degree of orientation, a polarized infrared spectral study in attenuated total reflection (ATR-FTIR) mode was performed. The dichroic ratio (between the absorbance measured with linearly polarized radiation parallel and orthogonal relative to the stretching direction, respectively) and the ATR absorbance ratio for the machine direction (MD) and transversal direction (TD) configurations both for the stretched and unstretched PET samples were measured.
摘要：
聚对苯二甲酸乙二醇酯（PET）薄膜是深入研究的主题，因为在应用中使用它们的极大兴趣，尤其是在医学上。从光学的角度来看,具有低拉伸程度的PET薄膜可以被认为是单轴材料，线性双折射及其色散的测定是非常重要的。此处应用了两种方法来估计这些参数：椭圆光度法和通道光谱法。椭圆光度法使用单色辐射；因此，对于给定的辐射波长值,测定PET膜的线性双折射。通道光谱方法允许估计可见光谱中大范围波长的线性双折射及其色散。记录了两个参数随波长增加而降低的情况。为了证明PET薄膜的微观结构和伸长引起的构象变化，并评估取向程度，进行了衰减全反射（ATR-FTIR）模式的偏振红外光谱研究。二色性比（在相对于拉伸方向平行和正交的线性偏振辐射测量的吸光度之间，分别），并测量了拉伸和未拉伸PET样品的纵向（MD）和横向（TD）配置的ATR吸光度比。
