Crystallinity conformation and

Further details of the theory and application of Raman spectroscopy in polymer studies can be found elsewhere (1. 9). However, vibrational frequencies of functional groups in polymers can be characterized from the spacing of the Raman lines and thus information complementary to IR absorption spectroscopy can be obtained. In addition, since visible radiation is used the technique can be applied to aqueous media in contrast to IR spectroscopy, allowing studies of synthetic polyelectrolytes and biopolymers to be undertaken. Conformation and crystallinity of polymers have also been shown to influence the Raman spectra Q.) while the possibility of studying scattering from small sample volumes in the focussed laser beam (-100 pm diameter) can provide information on localized changes in chemical structure. 

The conformations and crystalline structure of isolated fractions were analyzed by infrared and raman spectroscopy and convincing evidence was obtained, confirming macrocyclic structure. 

Polymer Conformation and Crystallinity. Beyond the stereoregularity and tacticity, the geometrical conformation of the polymer chain in the solid material could influence its electronic structure, through a modification of its valence band molecular orbitals. Indeed, a few years ago, very characteristic band structures were calculated for T, G, TG, and TGTG polyethylenes ( ). More recently. Extended Huckel crystal orbital calculations showed that for isotactic polypropylene, a zig-zag planar or a helical conformation resulted in significant changes in the theoretical valence band spectra, supporting the idea that conformation effects could be detected experimentally by the XPS method ( ). 

V. STRUCTURE OF POLYPROPYLENE AND OF THE HIGHER POLYOLEFINS STEREOREGULARITY, CONFORMATION AND CRYSTALLINITY... 

K where the influence of differences in intermolecular forces, conformation, and crystallinity become less significant. A table of heat capacity contributions of different chain units has been derived by Wunderlich and Jones (1969). An accuracy of about 5% in heat capacity can be achieved using the additivity scheme. This is a fair supplement to the body of measured values which in general seems to contain an error of 1—3% between duplicate sets of data from different laboratories. 

Having been extensively applied to characterize polymers, FTIR spectroscopy complements other teehniques in providing detailed information on the chain conformation transition and crystallinity of a polymer with nondestructive charaeteristies. ° The ehanges of chain conformation and crystallinity can be charaeterized by identifying FTIR spectral features of intensity, bandwidth, and position. 

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