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Analyse par résonance magnétique nucléaire des polycondensats urée–formol
Author(s) -
Duclairoir Christian,
Brial JeanClaude
Publication year - 1976
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1976.070200519
Subject(s) - urea formaldehyde , formaldehyde , polyoxymethylene , methylene , urea , aqueous solution , copolymer , chemistry , polymer chemistry , oligomer , solubility , nuclear magnetic resonance spectroscopy , nuclear chemistry , organic chemistry , polymer , adhesive , layer (electronics)
The oligomer reaction products between urea and formaldehyde were preliminarily studied by 60‐MHz NMR spectroscopy. This analytical method was extended to urea–formaldehyde copolymers and provided means to attempt to determine their molecular stucture. Prior to NMR analysis, dilution water was removed by freeze drying in order to avoid degradation and advancement of the resin. Lithium chloride was found to enhance polycondensate solubility in deuterated dimethylsulfoxide and to improve resolution of the spectra by reducing overlapping of the signals. It was then possible to proceed to a qualitative and quantitative analysis of urea–formaldehyde copolymer structure. Structural differences appeared between one‐step synthesized resins and those involving a second urea addition; in the latter case, the percentage of unreacted urea was calculated. The shape of the unresolved broad signal assigned to the various methylene groups yielded further information on the resins. A particular shoulder on the methylene signal gives evidence for polyoxymethylene sequences occurring in polycondensates synthesized from concentrated aqueous formaldehyde solutions.