Factors Influencing the Crystal Structure of Cellulose Triacetate

Abstract

A general examination of the effects of cellulose source and conditions of acetylation on the crystalline structure of cellulose triacetate has been carried out. Heat has been shown to markedly improve the lateral order of the structure and thereby to demonstrate the existence of two stable polymorphic crystalline forms, cellulose triacetate I and cellulose triacetate II. A general summary of conditions for achieving each structure is given.Conditions for transformation of triacetate I to triacetate II by heat and swelling are discussed, and the possibility of the reverse transformation is questioned.The action of a variety of organic swelling liquids on the ability of each form of triacetate to attain high lateral order is investigated: a mechanism is proposed to explain the observations.Proposals are made for unit cell dimensions of cellulose triacetate I an cellulose triacetate II crystals, and some speculation on their relationship to cellulose tructure is given.