Fourier-transform absorption spectra of NO2 at 298 K were recorded between 9000–15 000 cm−1 at Doppler-limited resolution (0.012 cm−1), in the region near the à 2B2–X̃ 2A1 conical intersection. The strong rovibronic bands are rather isolated and organized into polyads which can be assigned by the number of bending quanta of the à 2B2 state, corresponding to the transitions with the largest Franck–Condon factors. Around 9735 cm−1, where the origin of the à 2B2–X̃ 2A1 vibronic band system is located and up to about 11 200 cm−1, hot bands dominate the spectrum. The complexity of the spectrum increases with energy due to an increasing density of à 2B2 and X̃ 2A1 vibrational levels. The rotational structure is dense and irregular as already observed for higher bands.
ABSTRACT:The profile of molecular orientation within injection-molded tensile bars of the liquid crystalline copolyesters Vectra A, Vectra B, and Vectra C, as well as blends of these polymers, was investigated by means of wide-angle X-ray scattering (WAXS) using synchrotron radiation (HASYLAB, Hamburg). The local variation of chain orientation was resolved into steps of 100 mm. An even higher resolution was obtained by using the microfocus camera (focal spot 2 mm) at the European Synchrotron Radiation Facility (ESRF) in Grenoble. In Vectra A and in the blend of Vectra A and Vectra B, a smooth variation of the orientation was found being almost zero at the surface and showing its maximum at a distance of 0.6 mm from the surface. The orientation in Vectra B was rather fluctuating. The average chain orientation in the blend samples processed under the same conditions was higher than in samples of the pure liquid crystalline copolyesters. The mechanical properties of the different layers within the injection moldings were determined by cutting the samples into slices and measuring the stress-strain curves. For specimens of comparable orientation, it turned out that the blend samples had the largest values of Young's modulus and tensile strength. The synergism of orientation and mechanical strength was also found for different blend compositions, as well as in blends of Vectra B and Vectra C. Annealing the injection moldings above the melting point resulted in a rapid relaxation of the orientation, whereas the chain alignment persisted at lower temperatures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.