NOVEL CELLULOSE DERIVATIVES .2. SYNTHESIS AND CHARACTERISTICS OF MONO-FUNCTIONAL CELLULOSE PROPIONATE SEGMENTS

Mono-functional cellulose propionate segments for use in ter- or star-block polymers have been prepared by the depolymerization (step 1) of cellulose propionate in homogeneous phase using a mixture of HBr and propionic anhydride in methylene chloride solution. The anomeric mixture of glycosyl bromide has subsequently (step 2) been hydrolyzed in aqueous acetone. Functionality was determined by H-NMR spectroscopy of triethyl silane derivatives in combination with get permeation chromatography. The cellulose ester segments were semi-rigid, highly crystalline materials with melting points between 180 degrees and 250 degrees C. The lowest useful segment size, based on crystallinity and Mark-Houwink-Sakurada exponential factor, appeared to be DP 20, with an optimum around DP 40 to 50.