Chemistry

Characterization of polymers

Characterization of polymers



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Chromophores

The longer the conjugated system, the stronger the long-wave shift of the absorption band. It has been shown that the position of the electron band of such an unsaturated system depends little on the environment. Double bond systems and other groups with a characteristic electron band are called chromophores. Bands of gas molecules caused by electron excitation often have a pronounced vibrational fine structure as a result of the coupling with the molecular vibrations. In the case of incondensed phases, the fine structure of the bands is largely suppressed, and broad, poorly structured absorption areas are observed instead.

In the case of substances with an unknown molecular structure, the UV spectrum can provide valuable information about possibly existing chromophores. Data collections on UV spectra of organic molecules are available as an aid for this. In the case of polymers, however, there is usually no doubt about the nature of the double bond systems present, since the structure is largely known from the synthesis or from IR and NMR spectra.

Problems such as the determination of block lengths, degrees of tacticity, branching, etc. can not be solved at all with UV spectroscopy or less well than with other methods.


Video: 09-2 Polymers: Characterization Part 1 of 2 (August 2022).