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Molecular spectrum analysis is based on the quantum energy level transition in the material when the matter molecules interact with electromagnetic radiation, and the wavelength and intensity of the reflected, absorbed or scattered radiation are measured.

• Fourier Transform Infrared Spectrometer (FTIR)

Infrared spectroscopy has distinct characteristics in the qualitative analysis of polymer materials. Including chain composition, arrangement, configuration, conformation, branching, cross-linking, crystallinity, orientation change analysis. If there are some polar groups such as esters, acids, amides and imides in the polymer molecules, the band has a significant characteristic peak, which reflects the structure and existence of the polymer.

• Laser Raman Scattering Spectroscopy

Raman spectrum is a kind of scattering spectrum, which is particularly sensitive to the vibration of carbon-carbon, sulfur-sulfur, nitrogen-nitrogen single bond and multiple bonds. it is used to study the chemical composition, carbon chain skeleton, length, conformation, isomerization, unsaturation and conjugation of polymers. Compared with infrared, there are many similarities. For example, some absorption peaks of the compounds are identical in infrared wave number and Raman shift, which can be verified by each other. The difference between the two is that the infrared Abscissa is wavenumber, and its absorption peak is caused by the change of molecular dipole moment or charge distribution caused by vibration, and the Raman Abscissa is Raman shift. Its scattering is caused by the instantaneous polarization caused by the instantaneous deformation of the electron cloud distribution on the bond, resulting in induced dipole scattering when returning to the ground state, which is most suitable for the study of non-polar bonds and symmetrical molecules of polymers composed of the same atoms. The two are mutually exclusive and complementary to each other and are used for structural identification.

• Ultraviolet Absorption Spectrum

Ultraviolet-visible absorption spectroscopy utilizes the chromophore of a substance to absorb radiation in the 200-800nm spectral region to generate molecular valence electrons, causing n→π* and π→π* energy level transitions, and structure identification is carried out accordingly. In the research of polymer materials, it can be used to identify the structure of characteristic functional groups in polymers and additives, such as olefin, alkyne, benzene ring, carbonyl, carboxyl, azo, nitro, nitroso, nitrate, amide groups and so on, which have unsaturated bonds; the changes before and after the polymerization are detected to explore the polymerization mechanism; the composition of the copolymer and the kinetics of polymerization were studied through the change of absorption intensity and displacement caused by the concentration change of polymer and trace substance.

• Fluorescence Spectrum

Molecular fluorescence analysis is that the ground state molecule is excited to the excited state by the excited light source, and different wavelengths of fluorescence are produced when it is returned to the ground state. By measuring the fluorescence intensity, the fluorescence spectrum is obtained. Because the molecular structure of polymer materials is different, the absorption wavelength of ultraviolet light is different, and the fluorescence wavelength emitted when returning to the ground state is also different, this characteristic can be used for qualitative analysis. Quantitative analysis can be carried out based on the linear relationship between fluorescence intensity and concentration produced by dilute polymer solution. Fluorescence spectroscopy is useful for studying polymer solution morphology transformation, polymer blend compatibility and phase separation, polymer degradation and aging, polymer luminescent material properties, etc.

• Nuclear Magnetic Resonance Spectroscopy (NMR)

Nuclear magnetic resonance spectroscopy is a powerful tool for analyzing how the functional groups in polymers are connected. It is divided into 1H-NMR and 13C-NMR. Solid-state nuclear magnetic technology is often used for the structure exploration of crystals, microcrystalline powders, colloids, membrane proteins, protein fibers and polymers.