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Study of gelatin gels and the effect of urea on their formation
Author(s) -
Szczesniak Alina S.,
MacAllister Robert V.
Publication year - 1964
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.1964.070080329
Subject(s) - gelatin , urea , rigidity (electromagnetism) , polymer chemistry , polymer , chemistry , materials science , chromatography , organic chemistry , composite material
The effect of urea on gelatin gels was studied by measuring gel rigidity at different gelatin and urea concentrations. Rigidity of gels was expressed as the force necessary to depress the gel with a standard plunger a distance of 4 mm. In agreement with the data in the literature, a straight‐line relationship was obtained when gel rigidity was plotted against the square of gelatin concentration. This relationship held true in the presence and absence of urea and also for all urea concentrations tested. Urea had a marked effect on lowering the rigidity of gels and the ratio of rigidity to the square of gelatin concentration decreased with increasing molarity of urea. In order to gain some comprehension of the mechanism of gelatin gel formation, the rigidity values were interpreted in terms of the number of crosslinkages which would account for such rigidity values. The fraction of amino acid residues effective in crosslink formation was calculated from gel rigidity data by applying concepts developed by Flory and others for rubberlike elastic polymer networks. The state equation was modified in order to adapt it to the measurements of gelatin gel rigidities. Calculations indicate that about 1.7 amino acids per molecule were involved in crosslink formation in a 1.8% and 8.0 in a 1.0% gelatin gel set at 10°C. 1 M urea inhibited the formation of 30–45% of crosslinks and 4 M urea inhibited 90–100% of the bonds, the exact effect depending upon the concentration of gelatin.