The rheological and structural behavior of silylcellulosics derivatives

Abstract

ABSTRACT:The trimethylsilylcellulose (TMSC) samples were characterized in solution by osmometry, viscometry, and gel permeation chromatography. The Mark-HouwinkSakurada (M-H-S) equation coefficients were determined in chloroform, 1,1,1-trichloroethane, and o-xylene, in all cases the exponent "a" being higher than unit, this indicating a great stiffness of the macromolecules in solution. Also, the temperature dependence of the limiting viscosity number and M-H-S coefficients respectively for TMSC in o-xylene were studied. The exponent from M-H-S equation is also higher than unit, and increases linearly with the temperature. The GPC studies indicates a relative high polydispersity of the studied samples; the polydispersity index being situated between 2 and 3. The change of the crystalline structure as the result of silylation reaction was evidenced, the crystallinity of silyl derivatives depending on the substitution degree (DS), and the molecular weight. The viscous flow parameters for dilute solutions of trimethylsilylcellulose in o-xylene were determined in the temperature range 30 -70°C. The temperature dependence of the dynamic viscosity of the solutions obeys an Arrhenius-type equation in which the apparent activation energy is linearly dependent on both the solution's concentration and molecular weight. For preexponential factor no significant dependence on concentration and molecular weight was found. This behavior was attributed to the very great stiffness of the macromolecular chains.

Solution properties of triphenylsilyl cellulose

“…The silylation process was realized in a heterogeneous medium, comprising N , N ‐dimethylformamide (DMF) plus pyridine, by treating a suspension of activated cellulose with triphenylchlorosilane. Five samples of chemically purified cellulose with different degrees of polymerization (the same as those used in an earlier study14, 15) were used to obtain corresponding TPSC derivatives.…”