Modelling the crystalline deformation of native and regenerated cellulose

The molecular mechanics modelling of the deformation of a number of proposed structures for the crystalline regions of cellulose I-alpha, I-beta and II are reported. The structures used are from coordinates that have recently been reported, which have made particular reference to the ability to locate the positions of hydrogen bonds. By comparison to previously reported structures of cellulose, where the emphasis on this has also been made, and in a diagnostic way, it is shown that it is possible to make some conclusions as to their validity. The effect of removing the intramolecular hydrogen bonding is also reported. All structures, with one exception, are shown to be sensitive to this operation. Two approaches to the molecular mechanics modelling are reported, wherein the structures are minimised under restraint, by altering the c-spacing, within the COMPASS (TM) forcefield to obtain a simple chain stiffness value or alternatively by performing a full elastic constants determination for the unit cell.