VISCOMETRIC AND LIGHT-SCATTERING DETERMINATION OF DILUTE-SOLUTION PROPERTIES OF CELLULOSE DIACETATE

Eleven cellulose diacetate (CDA) fractions each with a combined acetic acid content of 55.5 wt% and a ratio of weight- to number-average molecular weight Mw/Mn=1.2–1.3 were carefully prepared. These fractions were not contaminated by gel-like materials. Dilute solution properties were measured in acetone and tetrahydrofuran (THF) at 25°C by a light scattering method, membrane osmometry, viscometry and gel permeation chromatography. The following Mark–Houwink–Sakurada (MHS) equations were established for CDA : [η]=0.133 Mw in acetone and [η]=0.0513 Mw in THF. The draining parameter X, as determined by various methods, was found to be less than four in acetone, and less than eight in THF. The molecular weight dependence of Flory’s viscosity parameters Φ, expressed as a (=dlnΦ/dlnM), was 0, 716 and 0.105 in acetone and THF, respectively. The CDA polymer chain is gaussian in THF, but is not so in acetone. That is, a (=dln(‹S›/M)/dlnM, where ‹S› is the mean-square radius of gyration in the unperturbed state) was −0.471 in acetone. The unperturbed chain dimensions A(=(6‹S›/M)) obtained by methods in which a and a (if necessary) were taken into account, agree well with each other, as the theory predicts. The value of A was 1.73 in acetone and 1.23 in THF. CDA is a typical semi-flexible polymer. The experimental second virial coefficient A can be reasonably explained in terms of the theory, in which a and a are considered. © 1979, The Society of Polymer Science, Japan. All rights reserved.