P.J. Hendra

The Raman spectra of oriented isotactic polypropylene

Abstract Measurements of the relative band intensity changes with orientation can be made in the FT Raman spectrometer on a wide range of isotactic polypropylene specimens. The usefulness of these changes in estimating orientation at the sampled point is considered. It is concluded that the method can be applied with caution.

The laser-Raman spectrum of polyethylene: The assignment of the spectrum to fundamental modes of vibration

Abstract By studying the anisotropic Raman scattering data from oriented samples of polyethylene it has been possible to make a full assignment of the observed Raman spectrum in terms of fundamental modes, overtones and combinations. Proper allowance has to be made for correlation effects and for Fermi Resonance. The results were confirmed by measurements of depolarization ratios in non-oriented specimens.

Surface hydration of aqueous γ-Al2O3 studied by Fourier transform Raman and infrared spectroscopy—I. Initial results

The hydration of γ-Al2O3 has been studied by Fourier transform (FT) Raman and infrared (IR) spectroscopy, and by X-ray diffraction (XRD). The initial findings are presented, along with a discussion of the possible causes for the major spectral changes that occur after hydration. The aims of the study and ongoing research are described.

Routine analytical Fourier transform Raman spectroscopy

A variety of applications of the technique of Fourier transform (FT) Raman spectroscopy using a near-infrared laser excitation source have now begun to emerge. The design and construction of a bench-top, analytical-grade FT Raman spectrometer are described. Its specifications are explained and its performance and convenience of use are reported. A variety of analytical applications of the FT Raman technique have been surveyed to demonstrate the versatility of the spectrometer.

Applications of Fourier Transform Raman spectroscopy in the synthetic polymer field

Abstract The application of FT Raman spectroscopy in the study of a wide range of polymer systems is discussed. The following have been included to give the reader an insight into the variety of areas which can successfully be studied using this important technique: the problem of crystallinity; nylons; poly(aryl ether ketone) and poly(aryl ether ether ketone); poly(aryl ether ether sulphone) and poly(aryl ether sulphone); epoxy resin curing; copolymers; copolymers of tetrafluoroethylene and hexafluoropropylene; polythioethers; and gels.

The application of Fourier transform Raman spectroscopy to the identification and characterization of polyamides. I : Single number nylons

Abstract High quality Fourier transform Raman spectra, substantially free from fluorescent background, have been obtained for twelve double-number nylons ranging from nylon 1,3 to nylon 10,10. These spectra, obtainable on a routine basis, prove to be highly characteristic and therefore of considerable value for analytical purposes. The characteristic trends observed in some regions of this series of spectra are investigated and discussed. A less detailed study suggests that Fourier transform Raman spectroscopy should also be of value for the characterisations of nylon co-polymers.

Comparative quantitative study on the crystallinity of poly(tetrafluoroethylene) including Raman, infra-red and 19F nuclear magnetic resonance spectroscopy

Abstract Wide-angle X-ray scattering (WAXS), 19 F nuclear magnetic resonance (n.m.r.) spectroscopy, differential scanning calorimetry (d.s.c.) and density measurements have been employed to determine the crystallinity of melt-quenched poly(tetrafluoroethylene) samples of different molecular weight. The methods have been checked for consistency before a routinely used infra-red (i.r.) spectroscopic and a recently devised Raman spectroscopic procedure have been correlated with crystallinity as derived by the four conventional methods. The usefulness of the two vibrational spectroscopic methods for determining crystallinity has then been assessed. It was found that WAXS, d.s.c. and density give consistent results in that they clearly show the same trends in the sample crystallinity. In contrast, neither free induction decay nor solid echo pulse sequence n.m.r. correlate with any of these methods, and possible reasons for this behaviour are discussed. Raman as well as i.r. data correlate well with the crystallinity by WAXS, d.s.c. and density. In this respect, both methods are found to be equally useful in estimating crystallinity.

The applications of near-infrared Fourier transform Raman spectroscopy to the analysis of polymorphic forms of cimetidine

Fourier transform (FT)-Raman spectroscopy, utilizing a near-infrared (Nd:YAG laser, at 1.064 μm) source was used to characterise the three anhydrous polymorphic forms A, B and C of the drug cimetidine (N″-cyano-N-methyl-N′ -[2-[(5-methyl-1H-imidazol-4-yl) methylthio]ethyl]guanidine). The FT-Raman spectra were free from fluorescence interference and had good signal-to-noise ratios. Each polymorph has a distinct spectrum, characterised by two regions, 1250-1050 cm−1 and 1500-1350 cm−1. This work demonstrates that it is possible to use FT-Raman spectroscopy to differentiate between polymorphic forms of the same compound.

The vibrational Raman spectra of C60 and C70

Abstract Vibrational Raman spectra have been obtained at 1 cm−1 resolution, for C60 and C70. For C60 the positions of the bands were in good agreement with theoretical predictions. For C70 27 bands were observed out of the total of 53 that were theoretically predicted. These data will permit refinement of calculations of vibrational lines appropriate to closed-cage carbon clusters. The technique for producing appreciable quantities of high purity C70 is described.

The vibrational spectrum of polypropylene

Abstract An account is given of the laser Raman spectrum of crystalline polypropylene over a wide range of temperatures. At cryogenic temperatures evidence for spectral bands characteristic of the unit cell is presented and explained. The effect of crystallinity and tacticity on the spectra are commented upon. Above the melting point some evidence was found for helical conformations.