Empirical Polarity Parameters of Celluloses and Related Materials

Abstract

Kamlet–Taft's α (hydrogen-bond donating (HBD) ability), β (hydrogen-bond accepting (HBA) ability), and π* (dipolarity/polarizability) parameters of native cellulose batches, carboxymethyl celluloses (CMCs), cellulose tosylates (CTs), and other derivatives with different degree of substitution (DS), chitine, amylose, amylopectine, and cellobiose are presented. Fe(phen)2(CN)2 [cis-dicyano-bis-(1,10)-phenanthroline-iron(II), (1)], Michler's ketone [bis-4,4′-(N,N-dimethylamino)benzophenone, (2)], 4-aminobenzophenone (3), coumarine 153 (4), and Reichardt's dye (5) were used as solvatochromic surface polarity indicators. The UV/Vis reflectance spectra of the five surface polarity indicators 1, 2, 3, 4, and 5, adsorbed on the samples from the organic solvents, were measured and the absorption maxima were used to calculate the α, β, π*, and ET(30) values of the polysaccharides surface. α, β, and π* depending on degree of crystallinity of the cellulose samples have been determined. α depends on both amount and strength of accessible acidic surface groups on the cellulose surface. It is significantly larger for crystalline sections than for amorphous parts. The π* scale is suitable for the classification of different cellulose batches, because it seems to be independent of inhomogeneities of the cellulose surface. The α-values of CMCs and CTs significantly decrease with increasing DS inasmuch the number of cellulosic-OH groups (Cell-OH) decreases. A slight increase of π* with DS is observed for CTs.