Supramolecular Composite Materials from Cellulose, Chitosan, and Cyclodextrin: Facile Preparation and Their Selective Inclusion Complex Formation with Endocrine Disruptors

We have successfully developed a simple one-step method of preparing high-performance supramolecular polysaccharide composites from cellulose (CEL), chitosan (CS), and (2,3,6-tri-O-acetyl)-alpha-, beta-, and gamma-cyclodextrin (alpha-, beta-, and gamma-TCD). In this method, [BMIm+Cl-], an ionic liquid (IL), was used as a solvent to dissolve and prepare the composites. Because a majority (>88%) of the IL used was recovered for reuse, the method is recyclable. XRD, FT-IR, NIR, and SEM were used to monitor the dissolution process and to confirm that the polysaccharides were regenerated without any chemical modifications. It was found that unique properties of each component including superior mechanical properties (from CEL), excellent adsorption for pollutants and toxins (from CS), and size/structure selectivity through inclusion complex formation (from TCDs) remain intact in the composites. Specifically, the results from kinetics and adsorption isotherms show that whereas CS-based composites can effectively adsorb the endocrine disruptors (polychlrophenols, bisphenol A), their adsorption is independent of the size and structure of the analytes. Conversely, the adsorption by gamma-TCD-based composites exhibits a strong dependence on the size and structure of the analytes. For example, whereas all three TCD-based composites (i.e., alpha-, beta-, and gamma-TCD) can effectively adsorb 2-, 3-, and 4-chlorophenol, only the gamma-TCD-based composite can adsorb analytes with bulky groups including 3,4-clichloro- and 2,4,5-trichlorophenol. Furthermore, the equilibrium sorption capacities for the analytes with bulky groups by the gamma-TCD-based composite are much higher than those by CS-based composites. Together, these results indicate that the gamma-TCD-based composite with its relatively larger cavity size can readily form inclusion complexes with analytes with bulky groups, and through inclusion complex formation, it can strongly adsorb many more analytes and has a size/structure selectivity compared to that of CS-based composites that can adsorb the analyte only by surface adsorption.