Project Number: 6435-44000-076-03
Project Type: Specific Cooperative Agreement

Start Date: Sep 01, 2009
End Date: Jan 31, 2012

Objective:
Overall project objectives include: Collecting the best available information on the structures within the cotton fiber; Constructing fundamental models of these structures at different size scales; Providing additional fundamental models that have partial surfaces of hydrophobic molecules; and Monitoring moisture movement through the model structure during molecular dynamics simulations. Specific aspects of this work to be carried out by the CCRC include development of improvements of atomistic models of cotton cellulose and their interaction with water.

Approach:
The main feature of this effort will be to examine the abilities of an improved version of the water model (TIP5P) and a parameter set that utilizes explicit lone pairs of electrons. The models will be examined for reproduction of known properties such as unit cell dimensions and retention of the geometric features of the cellulose structure. Distinctions in results between molecular dynamics and energy minimization will be explored. Necessary adjustments will be made to the modeling parameters to develop a final set. A model involving several smaller crystals will be devised to mimic a portion of a cotton fiber, and the behavior of interacting water will be observed. An ultimate goal, possibly not practical within the scope of this project, will be to gain insight on the division between “bound water” and “bulk water” and the sensitivity of the results to the exact details of the simulation. Deviations from the above plan are not necessarily expected but can be accommodated. For example, water models other than TIP5P might be more helpful, or other force field modifications other than the addition of explicit lone pairs may be more useful.