AbstractFive samples of triphenylsilyl cellulose (TPSC) are characterized in solution by osmometry, viscometry, and size exclusion chromatography. The isolated and purified cellulose ethers are prepared in a N,N‐dimethylformamide and pyridine medium under heterogeneous starting conditions and a nitrogen atmosphere by silylation of activated celluloses with triphenylchlorosilane at 115–120°C. TPSCs are characterized by their polydispersities and degrees of substitution by osmometry and viscometry in various solvents. The Mark–Houwink–Sakurada equation coefficients are evaluated in 1,1,1‐trichloroethane, chloroform, and o‐xylene at 30°C and in o‐xylene over a temperature range of 30–70°C. Values of 2.12–2.18 are obtained for exponent a. This indicates, in combination with low values of the preexponential factor (on the order of 10−12), strong stiffness of the macromolecular chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1257–1261, 2007