CONTINUOUS POLYMER FRACTIONATION OF POLYSACCHARIDES USING HIGHLY SUBSTITUTED TRIMETHYLSILYLCELLULOSE

Trimethylsilylcellulose (TMSC) was prepared from commercial cellulose with a mixture of hexamethyldisilazane and chlorotrimethylsilane in th e solvent system N,N-dimethylacetamide/lithium chloride. The soluble, highly silylated polymer (degree of substitution, DS 2.9) had a molar mass (M) over bar(w) of 500 kg/mol and a molecular non-uniformity U = ((M) over bar(w)/(M) over bar(n)) - 1 of 2.9. In order to investigate the principal suitability of a continuous polymer fractionation for po lysaccharides like cellulose derivatives and to obtain TMSC with diffe rent molecular weights and lower non-uniformity TMSC was fractionated by means of CPF (Continuous Polymer Fractionation), well-established i n the field of synthetic polymers. The samples were fractionated using a mixed solvent, composed of toluene and dimethyl sulfoxide, and char acterized by capillary viscometry, gel permeation chromatography (GPC) , and GPC-light scattering coupling. The molar masses of the fractions range from 110 to 600 kg/mol and their U values vary between 0.9 and 1.9. The intrinsic viscosities of TMSC in tetrahydrofuran at 25 degree s C and (M) over bar(w) are related by [eta] = K . M-w(a), where K = 0 .0089 mL/g and a = 0.82.