Optical Anisotropy of Polyethylene Terephthalate Films Characterized by Spectral Means

Area of Science:

• Materials Science
• Optics
• Polymer Science

Background:

• Polyethylene terephthalate (PET) films are vital for medical applications.
• Understanding optical properties like linear birefringence is crucial for stretched PET films, which behave as uniaxial materials.

Purpose of the Study:

• To determine the linear birefringence and its dispersion in PET films.
• To investigate the microstructure and conformational changes in PET films induced by elongation.
• To evaluate the degree of orientation in stretched and unstretched PET samples.

Main Methods:

• Ellipsometric method using monochromatic radiation to determine linear birefringence at specific wavelengths.
• Channeled spectra method to estimate linear birefringence and its dispersion across the visible spectrum.
• Polarized infrared spectral study in attenuated total reflection (ATR-FTIR) mode to analyze microstructure and orientation.

Main Results:

• Linear birefringence and its dispersion were measured for PET films.
• Both parameters showed a decrease with increasing wavelength.
• ATR-FTIR analysis provided insights into microstructure and conformational changes due to elongation.

Conclusions:

• The study successfully quantified optical properties of PET films using multiple methods.
• The findings highlight the relationship between wavelength, birefringence, and film orientation.
• The results contribute to the understanding and application of PET films in various fields, especially medicine.