COMPARATIVE INVESTIGATIONS ON THE SILYLAT ION OF CELLULOSE WITH MONOFUNCTIONAL AND MULTIFUNCTIONAL ORGANOSILANES

Cellulose oi DP = 190 dissolved in the LiCl/dimethylacetamide system w as reacted with different mono and polyfunctional substituted silanes to silyl ethers of cellulose, and this homogeneous course oi reaction was compared in some experiments with the corresponding heterogeneous one. The isolated and purifed reaction products were characterized by their Si-content, by their solubility or swelling value, resp., and in some cases by C-13 and Si-29 NMR spectroscopy. The following priority with regard to the maximal DS obtained was observed by the reaction o f cellulose with Selected monofunctional silanes under defined reactio n conditions (Me)(3)SiCl > (Me)(3)SiN(Et)(2) > (Me)(3)SiNHSi(Me)(3) > (Me)(3)SiOEt > (Me)(3)SiOSi(Me)(3). For preparing highly substituted t rimethyisilylcellulose of DS = 3,0, the (Me)(3)SiN(Et)(2) was found to be most suitable. In medium DS-range, a substitution of the C-6 and C -2 position of the AGU was observed without regioselectivity. With pol yfunctional silanes gel formation due to covalent crosslinking caused by an at least bifunctional reaction oi the silane was observed with e xception of (Me)(2)Sl(OEt)(2) leading to a non-crosslinked organosolub le silyl cellulose. As revealed by Si-29 NMR spec tra, sell-condensati ons of the polyfunctional silanes to oligosiloxane structures has to b e considered besides the substitution of cellulose OH-groups.