Synopsis'"C NMR has been found to be useful in elucidating the structure of a complex condensation product. Study of a divinylbenzene-p-cresol oligomer mixture has shown structural units consisting of approximately 85% 2,6-substituted p-cresol, 610% 2,5-substituted p-cresol, and 2-substituted p-cresol endgroups.
Amino acid containing polymers were synthesized by heating mixtures of aspartic acid, glutamic acid, glycine, alanine, valine, leucine, isoleucine, and proline in the absence of water at temperatures of 180" to 190°C for several hours. The resulting product was fractionated by dialysis, gel filtration, and chromatography and electrophoresis on paper. The larger polymers were found to be rich in aspartic acid and poor in proline, while the smaller molecules were rich in glutamic acid and contained proline as a signifcant constituent. The N-terminal positions are believed to be occupiedlargely by pyroglutamic acid, while the C-terminalpositions are comprised exclusively of aliphatic amino acids. Aspartic acid and glutamic acid were individually treated to the polymerization conditions. Little reaction of aspartic acid was observed, but glutamic acid formed a melt and upon cooling a glass. Investigation of this product indicated it to be a highly hydrogen bonded system of pyroglutamic and glutamic acids. The model system of glutamic acid and decylamine produced under polymerization conditions, the decylamide of pyroglutamic acid. The accumulated results suggest a model for thermal polymerization.
13C NMR spectra of a series of aminoethylene‐ethylenesulfonate copolymers of varying composition have been taken. It has been found that the methylene groups of the copolymer are clear indicators of amine–amine, sulfonate–sulfonate, and amine–sulfonate sequence diads. Combinations of peak areas with composition data from elemental analysis allows quantitative determination of diad frequencies. Once elemental analysis data for several copolymer compositions have been obtained ratios of peak areas may be used to determine unknown polymer compositions with excellent sensitivity.
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