Preparation of 6-O-(4-alkoxytrityl)celluloses and their properties

Cellulose was reacted with a series of 4-alkoxytrityl chlorides (C(n)TC1, n: number of carbon atoms in a saturated alkyl chain) under homogeneous reaction conditions in LiCl-N,N-dimethylacetoamide to give a series of 6-O-(4-alkoxytrityl)celluloses (CnTC) with a high degree of substitution (DS), from 0.94 to 0.99, and with high regioselectivity at the 6-O position. Solubility of the CnTC in nonpolar solvents depended on the alkyl chain length: as the alkyl chain lengthens, cellulose derivatives become more hydrophobic and are readily soluble in nonpolar solvents, but not in polar solvents. Acetates of the C-4-C18TC (C-4-C18TCAc) showed anisotropic structures over melting temperatures (T-m) examined under a polarized optical microscope (POM). Over isotropization temperatures (T-i), flow birefringence were detected for C-12-C18TCAc. The T-m and T-i decreased linearly with an increasing number of carbon atoms in the alkyl substituent. Wide-angle X-ray scattering (WAXS) studies of CnTC indicated that the fully extended side chains were perpendicular to the polymer backbone and interdigitated. These CnTC with the improved solubility may be used as starting materials for further derivatization focused on the secondary hydroxyl groups at the C-2 and C-3 positions.