Folding chain model and annealing of cellulose

A folded chain model of cellulose fine structure has been developed, together with a new hypothesis on cellulose “weak links”. Essentially, single cellulose molecules are folded back and forth in the (101) plane to form “platellites” which are the smallest physical and structural unit of crystalline cellulose. The average fold length in the platellites corresponds to the levelling‐off DP. The glucosidic bonds at the folds are weak links due to a loop conformation of the chain. The morphological transition of cellulose during mercerization has been examined with reference to the folding chain model. It is envisaged that the transition is the result of a partially restricted annealing of the cellulose crystals under the action of the swelling agent. Thus, low‐temperature annealing of cellulose shortens the fold length of the molecule and results in the well known mercerization process; high‐temperature annealing, on the other hand, generates at least a partial reversal of the mercerization. This hypothesis is found to agree very well with the known facts in the literature and is further supported by some experimental evidence.