Photooxidative degradation and conformational changes in syndiotactic polypropylene/clay nanocomposites.

Syndiotactic polypropylene nanocomposites based on layered silicates in various proportions were subjected to prolonged (246 h) ultraviolet (UV)-c irradiation. Fourier transform infrared (FT-IR) spectroscopy was used in order to investigate the molecular alterations of the polymeric matrix during the UV exposure relative to the concentration of nanoclay. It was found that a significant increase of the helical conformation upon the irradiation took place as a result of scissions of the polymeric chains.

Vibrational spectroscopic study on the origin of stress oscillation during step-wise stretching in poly(ethylene terephthalate).

The origin of the phenomenon of stress oscillation during step-wise stretching at room temperature for amorphous poly(ethylene terephthalate) (PET) was investigated using vibrational spectroscopy. For the first time, transmission Fourier transform infrared (FT-IR), attenuated total reflection (ATR) FT-IR, and micro-Raman spectroscopies were used in order to investigate the correlation of the orientation of the molecular chains, their conformational transformations, and the appearance of stress-induced crystallization to the phenomenon of stress oscillation during the step-wise stretching procedure. The phenomenon of stress oscillation occurs when amorphous PET is exposed to mechanical stress during which the extension rate is increased in a step-wise manner.

Molecular composition and orientation of interstitial versus surface silicon oxides for Si(111)/SiO2 and Si(100)/SiO2 interfaces using FT-IR and X-ray photoelectron spectroscopies.

This work represents a characterization study of silicon oxide on Si(111) and Si(100) surfaces intended for use as substrates in organic light-emitting diodes (OLEDs) on chip devices. Samples have been prepared using either native oxide formation or thermal oxidation, and they have also been treated for activation of hydroxyl groups on their surface. Both Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) have been used in order to understand the molecular orientation as well as the chemical composition of the various oxide types formed during these different oxidation processes.