ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
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. 1M urea inhibited the formation of 30-45% of crosslinks and 4M urea inhibited 90-100% of the bonds, the exact effect depending upon the concentration of gelatin.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1964.070080329
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