title: Isolation of thermally stable cellulose nanocrystals by phosphoric acid hydrolysis.
abstract: On account of their intriguing mechanical properties, low cost, and renewable nature, high-aspect-ratio cellulose nanocrystals (CNCs) are an attractive component for many nanomaterials. Due to hydrogen bonding between their surface hydroxyl groups, unmodified CNCs (H-CNCs) aggregate easily and are often difficult to disperse. It is shown here that on account of ionic repulsion between charged surface groups, slightly phosphorylated CNCs (P-CNCs, average dimensions 31 ± 14 × 316 ± 127 nm, surface charge density = 10.8 ± 2.7 mmol/kg cellulose), prepared by controlled hydrolysis of cotton with phosphoric acid, are readily dispersible and form stable dispersions in polar solvents such as water, dimethyl sulfoxide, and dimethylformamide. Thermogravimetric analyses reveal that these P-CNCs exhibit a much higher thermal stability than partially sulfated CNCs (S-CNCs), which are frequently employed, but suffer from limited thermal stability. Nanocomposites of an ethylene oxide-epichlorohydrin copolymer and H-CNCs, S-CNCs, and P-CNCs were prepared, and their mechanical properties were studied by dynamic mechanical thermal analysis. The results show that P-CNCs offer a reinforcing capability that is comparable to that of H-CNCs or S-CNCs.
authors: Adolphe Merkle Institute and Fribourg Center for Nanomaterials, University of Fribourg, Route de l'Ancienne Papeterie, 1723 Marly, Switzerland.
authors: Sandra
authors: S
authors: Camarero Espinosa
authors: Tobias
authors: T
authors: Kuhnt
authors: E Johan
authors: EJ
authors: Foster
authors: Christoph
authors: C
authors: Weder
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis* / Q000737:chemistry; D002482:Cellulose / Q000737:chemistry*; D004811:Epichlorohydrin / Q000737:chemistry; D005027:Ethylene Oxide / Q000737:chemistry; D006868:Hydrolysis; D052578:Ionic Liquids / Q000737:chemistry*; D053761:Nanocomposites / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010756:Phosphoric Acids / Q000737:chemistry* / Q000378:metabolism*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D052578:Ionic Liquids; D010756:Phosphoric Acids; D011108:Polymers; D004811:Epichlorohydrin; D002482:Cellulose; C030242:phosphoric acid; D005027:Ethylene Oxide