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United States Department of Agriculture

Agricultural Research Service

Research Project: STRUCTURE AND MOISTURE AS DETERMINANTS OF COMMERCIALLY IMPORTANT COTTON FIBER PROPERTIES

Location: Cotton Structure and Quality Research

Title: Simulation Studies of the Wetting of Crystalline Faces of Cotton Cellulose

Authors
item Venkataraman, Pradeep -
item Ashbaugh, Hank -
item Johnson, Glenn
item French, Alfred

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: February 10, 2010
Publication Date: April 28, 2010
Citation: Venkataraman, P., Ashbaugh, H., Johnson, G.P., French, A.D. 2010. SIMULATION STUDIES OF THE WETTING OF CRYSTALLINE FACES OF COTTON CELLULOSE. Proceeding of the 2010 National Cotton Council Beltwide Cotton Conference, January 5-7, 2010, New Orleans, Louisiana. p. 1577-1580.

Interpretive Summary: Interactions of water with cotton cellulose are important because the amount of moisture in cotton has a substantial effect on the physical properties of cotton fibers as well as economics of handling cotton and comfort when wearing it. The present work concerns a computer modeling study of the behavior of a droplet of water placed on different surfaces related to cotton. Because the cellulose molecules of cotton fibers occur as crystals, the model droplet was placed on model crystal surfaces and the movement of water over the surfaces was monitored. Additionally, the crystal surfaces were modified by replacing the usual hydroxyl groups of cellulose with methyl groups, changing the surface from water-attracting to water-repelling. Different distributions of the methyl groups simulated different modified textiles that would impart “moisture management” features to garments. This information is primarily of interest to scientists trying to improve cotton products with chemical treatments.

Technical Abstract: Models of the surfaces of nano-sized cellulose crystals were constructed and a model droplet of water was placed on each. Then, the model atoms were given motion that corresponds to room temperature (a molecular dynamics simulation), and the spreading of the water over the surfaces was studied. Besides the surfaces that would be found for native cellulose, surfaces were also constructed with varying amounts of methyl groups that replaced the hydroxyl groups. Those methylated surfaces were devised as a start to understanding treatments of cotton fabrics for moisture management. The water was not expected to be so attracted to those groups, and that was the case. Although the water droplet did not spread out so much on the heavily methylated surfaces, it did bridge small regions of methylated cellulose. When the cellulose was completely methylated, the water droplet retained much of its original shape, and contact angles could be estimated for the water on the more heavily methylated surfaces. For the native cellulose crystals, however, the water spread out so that a partial monolayer was formed. Not enough water molecules were in the droplet to completely cover the surface.

Last Modified: 8/1/2014
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