Molecular Properties of Milkweed Cellulose

The seed hairs of the common milkweed (Asclepias syriaca, L.) have been found to contain 39.6% alpha-cellulose, 35.3% pentosan (chiefly xylan), and 15.1% lignin. The alpha-cellulose fraction was entirely composed of anhydroglucose, the hemicellulose por tion of anhydroxylose units. The original material, in addition, also contained minor amounts of arabinose and uronic acid residues. Direct nitration of the untreated fibers gave a cellulose nitrate with glucose as the only constituent sugar in a yield corresponding to a content of 29% cellulose in the original material. The average degree of polymerization of the nitrate was 5800, as determined viscometrically with corrections applied for the effects of rate of shear and nitrate substitution on the intrinsic viscosity. Fractional precipitation of the nitrate derivative was carried out with acetone water as the solvent-nonsolvent system. The chain-length distribution had only one peak and exhibited a considerable right-hand skewness. The lower D.P. limit was 2500 and the upper 8000, with the maximum located at a D.P. of 4000.