Method for determining structure and molecular weight of perfluoropolyether based on nuclear magnetic resonance

Abstract

The invention discloses a method for determining the structure and molecular weight of perfluoropolyether based on nuclear magnetic resonance. The method specifically comprises the following steps: measuring to obtain a fluorine spectrogram of a perfluoropolyether solution, calculating the peak area of fluorine atoms with end group fluorine characteristics of perfluoropolyether and the peak area of fluorine atoms of a main chain repetitive unit through an area normalization method, and speculating and calculating the structure and molecular weight of the perfluoropolyether according to a peakarea ratio and the absorption peak intensity. The method provided by the invention can simultaneously represent the structure and the molecular weight of the perfluoropolyether, is high in accuracy, convenient and rapid to operate, environment-friendly and low in experimental cost, can be applied to determination of the structure and the molecular weight of the perfluoropolyether prepared by a photooxidation method, and has important practical values.

Description

technical field [0001] The invention belongs to the technical field of instrumental analysis, and in particular relates to a method for determining the structure and molecular weight of perfluoropolyether based on nuclear magnetic resonance. Background technique [0002] Fluorinated surfactants refer to a class of surfactants containing fluorine atoms in the carbon-carbon chain. When the concentration of fluorinated surfactants is as low as 0.01-0.2 wt%, the surface tension of the aqueous phase system can be reduced to 15 -20mN / m; Its chemical properties are extremely stable, and it has the characteristics of anti-oxidation, acid and alkali resistance and high temperature resistance. The use of fluorine-containing surfactants in the synthesis of fluorine-containing emulsions, rubbers and resins can not only obtain high molecular weight fluorine-containing polymers, but also improve the stability of fluorine-containing high polymer particles. [0003] In the field of fluorin...

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Problems solved by technology

[0004] In the prior art, perfluoropolyether is mainly produced by photooxidative reaction of hexafluoropropylene and chlorotrifluoroethylene in the presence of oxygen to generate long-chain fluorocarbon ether, and then hydrolyzed. Its structure and molecular weight are measured by its One of the key parameters of application performance, but due to the influence of perfluoropolyether's own characteristics, gel permeation chromatography can only be used to measure its weight average molecular weight, and the choice of mobile phase is difficult and time-consuming. In addition, a large number of The use of organic solvents will also cause pollution to the environment, and the frequency of chromatographic column replacement is high, and the test cost remains high; although the viscosity method is simple in equipment and easy to operate, its measurement results have large errors and have great limitations; The determination of the base analysis method not only needs to determine the chemical structure of perfluoropolyether by means of other analysis methods, but also requires the end of the molecular chain of perfluoropolyether to have groups (such as carboxyl and ester groups) that can be used for chemical analysis. Clear high molecular weight perfluoropolyether, the method has a large analytical error

[0005] The NMR method has been widely used in the structural analysis and molecular weight calculation of organic compounds due to its high sensitivity, high accuracy, and rapid analysis. Reporting of the structure and molecular weight methods

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