- Oak Ridge National Laboratory
A protocol was developed to freeze-trap (at 150 K) cellulose as it is undergoing liquid ammonia pretreatment, and then to collect X-ray diffraction data from the freeze-trapped reactants as the reaction is allowed to proceed and ammonia is allowed to melt and then evaporate, leaving ammonia-cellulose I. Cellulose adopts a new two-chain crystal form, which we call low temperature phase ammonia-cellulose I (two-chains and ~ten ammonia molecules within a unit cell of a = 15.49 Å, b = 11.35 Å, c = 10.42 Å and γ = 143.5°). A schematic model was developed that is characterized by sheets of hydrophobically stacked cellulose-chains with hydrophilic channels between them that are filled with ammonia molecules. Neighboring chains in these sheets have either different conformations or are staggered with respect to each other. As ammonia is allowed to evaporate, the unit cell size is reduced by a factor of two as the two independent chains become identical.
|Publication status||Published - 2014|
|MoE publication type||A1 Journal article-refereed|