Properties of an amphoteric cellulose derivative containing anionic carboxymethyl and cationic 2-hydroxy-3-(trimethylammonio) propyl substituents

An amphoteric cellulose derivative, O-carboxymethyl-O-2-hydroxy-3-(trimethylammonio) propylcellulose (CM-HTMAPC), was prepared by the etherification of O-carboxymethylcellulose (CMC) with (3-chloro-2-hydroxy-n-propyl)-trimethylammonium chloride in a NaOH solution. Apparent molecular sizes of the amphoteric cellulose derivative in aqueous solutions of different NaCl concentrations under various pH conditions were investigated by gel permeation chromatography (GPC), and results were evaluated in terms of inter- and intramolecular ionic interactions. Relation between GPC and viscosity results was also discussed. A titration method to determine the apparent acidic dissociation constants of carboxymethyl substituents was developed and the effect of cationic substituents on apparent acidic dissociation constants was examined. ©1995 John Wiley & Sons, Inc.     

The nanostructure of kraft pulp 1: evaluation of various mild drying methods using field emission scanning electron microscopy

Wood pulp fiber consists of carbohydrate fibrils containing crystalline cellulose microfibrils of a few nanometer width. The structure of the fibril in water is currently unclear due to the difficulty of imaging pulp fiber in water at nanometer resolution. An alternative method is to observe the sample dried with a mild drying method to preserve the structure of the wet sample. In this study, we studied softwood kraft pulp fibers which were dried with various mild drying methods and then imaged by field emission scanning electron microscopy at nanometer resolution. Both mild dried samples, as well as air dried samples, showed 10–20 nm wide fibrils, the width of which corresponded to a crystalline cellulose microfibril or bundles of them. The mild dried sample, which was critical point dried with liquid CO₂ (CPD), mainly showed 20–40 nm thick fibrils, in addition to the 10–20 nm fibrils. The existence of the thick fibril implies that the fibril itself has a swelling nature in water, although the possibility that the thick fibril was an artifact of the CPD process could not be excluded. Further investigation as to the extent that the thick fibrils found in the CPD samples reflect the nanostructure of pulp fiber in water is warranted.     

Chain behavior of an amphoteric cellulose derivative: O-carboxymethyl-O-2-hydroxy-3-(trimethylammonio) propylcellulose

The ¹³C NMR spin-lattice relaxation times (T₁) of anhydroglucose units vary with the number of substituents, and the T₁ values of unsubstituted anhydroglucose units of O-carboxymethylcellulose are longer than those of amylose. Those results indicate that in water, the rotational motions of anhydroglucose units of cellulose derivative are quite important local motions contributing to the ¹³C NMR spin-lattice relaxation, and within a cellulose chain, anhydroglucose units rotate with different degrees of freedom depending on their environment. Moreover, the ¹³C NMR spin-lattice relaxation data indicate that the mobilities of ionic substituents are dependent on substitution positions as well as their ionic interaction. © 1995 John Wiley & Sons, Inc.