Properties of regioselectively substituted anionic cellulose polyelectrolytes

Influence of ionic liquid-like cationic pendants composition in cellulose based polyelectrolytes on membrane-based CO2 separation

Cellulose acetate (CA) is an attractive membrane polymer for CO₂ capture market. However, its low CO₂ permeability hampers its application as part of a membrane for most relevant types of CO₂ containing feeds. This work investigates the enhancement of CA separation performance by incorporating ionic liquid-like pendants (1-methylimidazol, 1-methylpyrrolidine, and 2-hydroxyethyldimethylamine (HEDMA) on the CA backbone. These CA-based polyelectrolytes (PEs), synthesised by covalent grafting of cationic pendants with anion metathesis, were characterised by NMR, FTIR, DSC/TGA, and processed into thin-film composite membranes. The membrane performance in CO₂/N₂ mixed-gas permeation experiments shows a decrease in CO₂ and N₂ permeability and an initial decrease and then gradual increase in CO₂/N₂ selectivity with increasing HEDMA content. The amount of HEDMA attached to the CA backbone determines overall separation process in bifunctional PEs. This indicates that the hydroxy-substituted cationic pendants alter interactions between PEs network and permeating CO₂ molecules, suggesting possibilities for further improvements.

Exploitation of reactivity and selectivity in cellulose functionalization using unconventional media for the design of products showing new superstructures

A variety of new cellulose solvents was investigated toward their potential as media for the functionalization of the polyglucane. Thus, mixtures of dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF), N-methylmorpholine-N-oxide (NMMNO)/DMSO, melts of LiClO(4).3H(2)O, and aqueous solutions of Ni(tren)(OH)(2) [tren = tris(2-aminoethyl)amine] were applied as reaction media. In case of the new solvent, DMSO/TBAF its usefulness for derivatization reactions including the etherification with sodium monochloroacetate and the acylation with vinyl esters of carbonic acids was studied. The structural features of the products were analyzed by means of (1)H NMR spectroscopy (after depolymerization or peresterification), (13)C NMR spectroscopy, and HPLC after complete hydrolytic chain degradation. The results were compared with those obtained from derivatives prepared using the solvent N,N-dimethylacetamide (DMAc)/LiCl and conventional, heterogeneous synthesis. It can be shown that in case of carboxymethylation reactions the reaction medium applied has a drastic influence both on the course of reaction and on the structural features of the products. A highly efficient tool was found to be atomic force microscopy (AFM), showing remarkable differences in the superstructures of the differentially synthesized derivatives.