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:
Previous investigations on the solution properties of sodium carboxymethylcellulose (CMC) have led to the conclusion that crystalline cellulose regions, remaining after processing act as binding or crosslinking sites for the establishment of a fraction comprised of swollen gels or aggregates in solution. The present paper deals with recent work which has led to a broader characterization of the degree of aggregation of CMC and its control in solution. Stages of disaggregation are defined for CMC when added to a solvent, ranging from a polymer particle unaffected by solvent through various degrees of swelling to a state of complete dispersion. Examples are given of these various disaggregation stages which were attained and controlled by varying the solvation power and/or ionic strength of the solvent. Degrees of disaggregation were characterized by broad variations in rheological behavior. Viscosity differences of several hundredfold as well as other physical changes in the solutions were found. The results are interpreted to mean that the numerous binding centers which cause CMC aggregation have a wide distribution of strengths. The addition of CMC to a good solvent causes the weaker binding forces to be destroyed and the stronger to remain intact, imparting rheological properties commensurate with the resulting degree of aggregation. The use of a poorer solvent or the addition of a simple electrolyte causes fewer binding centers to be destroyed, and a corresponding change in dispersion properties. Little, if any, re-formation of broken binding centers has been detected. Known and proposed forces involved in the dispersion of macromolecules into solvent are discussed and applied to observations from the present work.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1961.070051503
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