The surface of cellulose nanocrystals, prepared by sulfuric acid hydrolysis of cotton, was rendered cationic through a reaction with epoxypropyltrimethylammonium chloride. The resultant nanocrystal suspensions were characterized by z-potential, conductometric titration and polarized light microscopy. Atomic force microscopy (AFM) showed no change in the size or shape of the nanocrystals, but the functionalization process reversed the surface charge and led to a reduction of the total surface charge density. These modifications led to stable aqueous suspensions of nanocrystalline cellulose with unexpected gelling and rheological properties. Shear birefringence was observed, but no liquid crystalline chiral nematic phase separation was detected.

Abstract:The irradiation of pulp is of interest from different perspectives. Mainly it is required when a modification of cellulose is needed. Irradiation could bring many advantages, such as chemical savings and, therefore, cost savings and a reduction in environmental pollutants. In this account, pulp and dissociated celluloses were analyzed before and after irradiation by electron beaming. The focus of the analysis was the oxidation of hydroxyl groups to carbonyl and carboxyl groups in pulp and the degradation of cellulose causing a decrease in molar mass. For that purpose, the samples were labeled with a selective fluorescence marker and analyzed by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), refractive index (RI), and fluorescence detectors. Degradation of the analyzed substrates was the predominant result of the irradiation; however, in the microcrystalline samples, oxidized cellulose functionalities were introduced along the cellulose chain, making this substrate suitable for further chemical modification.

Herein, we explore the intrinsic ability of cellulose dissolved in NaOH(aq) to reversibly capture CO 2 . The stability of cellulose solutions differed significantly when adding CO 2 prior to or after the dissolution of cellulose. ATR-IR spectroscopy on cellulose regenerated from the solutions, using ethanol, revealed the formation of a new carbonate species likely to be cellulose carbonate. To elucidate the interaction of cellulose with CO 2 at the molecular level, a 13 C NMR spectrum was recorded on methyl α-D-glucopyranoside (MeO-Glcp), a model compound, dissolved in NaOH(aq), which showed a difference in chemical shift when CO 2 was added prior to or after the dissolution of MeO-Glcp, without a change in pH. The uptake of CO 2 was found to be more than twice as high when CO 2 was added to a solution after the dissolution of MeO-Glcp. Altogether, a mechanism for the observed CO 2 capture is proposed, involving the for-

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Cationization of cellulose under aqueous alkaline conditions was studied. Two new epoxy reagents, N-oxiranylmethyl-N-methylmorpolinium chloride and 2-oxiranylpyridine, were used for preparation of cationic cellulose ethers. Using the first agent, cationic ethers were obtained in one step, whereas the latter one yielded a reactive intermediate used as a precursor for two different cationizations. Etherification with the commonly used 2,3-epoxypropyltrimethylammonium chloride was also performed and used as a reference reaction. By changing water content in the reaction mixture two groups cellulose ethers with different degrees of cationization were prepared. As expected, reducing the water content resulted in a higher degree of etherification and hence a more pronounced cationic character of the obtained ethers. Characterization by FTIR, elemental-and gravimetric analysis confirmed the formation of the desired ethers. Their ability to interact with water and adsorb the acid dye, methyl orange, was also studied, confirming further introduction of the cationic substituents and revealing different reactivities of the used epoxy reagents. From characterization, it could be concluded that N-oxiranylmethyl-N-methylmorpholinium chloride exhibits higher reactivity toward cellulose than both the reference compounds and 2-oxiranylpyridine.

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