The acid‐catalyzed degradation of cellulose in the range of medium and low degrees of polymerization

The acid‐catalyzed degradation of cotton cellulose with number‐average degrees of polymerization DPn < 2000 was studied, using a 0,5 M aqueous KHSO4 solution as degradation agent and applying throughout a degradation temperature of 60°C. The data obtained show, contrary to what happens for the same molecular weight range at 40°C, a systematic decrease of the reaction rate, the initial reaction rate being the lower, the lower the initial degree of polymerization. For DPn ≲ 350 a simultaneous decrease of the capability of the cellulose to form derivatives had been observed, manifesting itself in a systematic decrease of the ratio of the intrinsic viscosities of cellulose nitrate in acetone and of the unsubstituted cellulose in Cu‐ethylenediamine [η] ./[η] with the time of degradation. The molecular weight distribution, as far as investigated, seems to retain the character of a most probable distribution also at very extended stages of the degradation. A preliminary hypothesis is put forward stating that beginning with a certain DPn going downwards supermolecular rearrangements may occur provoking a systematic decrease of the accessibility of the cellulose against degradation and also derivatization agents.