One-Pot Preparation of Carboxylated Cellulose Nanocrystals and Their Liquid Crystalline Behaviors

Abstract

Carboxylated cellulose nanocrystals (CNCs-COOH) have attracted great attention for their potential applications in reinforcing polymer materials and surface modification. Herein, we developed a low-cost approach to prepare CNCs-COOH from pulp with high yield at mild reaction conditions (50 °C, 1 wt % sulfuric acid medium) using potassium permanganate (KMnO 4 ) and oxalic acid (OA, H 2 C 2 O 4 ) as the oxidizing and reducing agents, respectively. The oxidant dosage in this strategy is much lower than that in a conventional TEMPO method, and the yield of CNCs-COOH can reach as high as 68.0%, with a carboxylate content of 1.58 mmol/g. In this reaction system, the presence of the OA can complex with Mn 3+ to form [Mn(C 2 O 4 2− )] + and prevent the Mn 3+ from being reduced to Mn 2+ , leading to the strong oxidizing capacity of the reaction system maintained for a longer time. Atomic force microscopy analysis showed that rod-like CNCs were obtained with an average size of 10−22 nm in diameter and 150−300 nm in length. The crystal structure of as-prepared CNCs-COOH was nearly unchanged, and the crystallinity was 89.2% based on WAXD analysis. Of particular interest, CNCs-COOH suspension with high concentration (>6 wt %) also exhibited the same intriguing chiral nematic liquid crystalline self-assembly behaviors as sulfate CNCs prepared by traditional H 2 SO 4 hydrolysis method. This study provides an efficient and cost-effective way to fabricate CNCs-COOH, leading to great potential applications in constructing advanced functional material.

A Promising Energetic Polymer from Posidonia oceanica Brown Algae: Synthesis, Characterization, and Kinetic Modeling

“…XRD analysis was performed to obtain information about alterations in crystalline structure and crystallinity index of all studied samples before and after the nitration process. As can be seen from Figure a–c, the XRD patterns of POBA‐C, POBA‐MCC, and C‐MCC exhibited the typical diffraction peaks of cellulose I allomorph detected at 2θ values around 14.8°, 16.2°, 22.4°, and 34.4 °, with assigned planes of 10, 110, 200, and 004, respectively . After nitration, the experimental diffractograms of conventional NC1 and NC2 as well as MCCN1 and MCCN2 (Figure d) showed the disappearance of the diffraction peaks attributed to 10, 110, and 004, together with the appearance of new peaks at around 2θ = 12.5 ° and 20 °.…”

Magnetic nanocomposite based on polyacrylic acid and carboxylated cellulose nanocrystal for the removal of cationic dye

“…25 In the XRD spectrum of M3D-PAA-CCN, along with the Fe 3 O 4 peaks a new peak (200) at 21.3 yet again conrmed the presence of CCN. 55,56 The elemental compositions of M3D and M3D-PAA-CCN were obtained from both XPS and EDX (ESI, Fig. S2 †) analyses.…”

Liquid crystal behavior of cellulose nanoparticles‐ethyl cellulose composites: Preparation, characterization, and rheology

“…For all samples, the broad bands ranged from 3380 to 3430 cm −1 are assigned to the stretching vibrations of -OH; while the bands near 2900 cm −1 is due to the stretching vibrations of C H. The characteristic bands near 1640, 1430, and 1370 cm −1 are assigned to the OH bending of adsorbed water (hydrophilic hydroxide radical in the cellulose), H C H, and O C H in-plane bending vibrations. [64][65] Additional bands near 1115, 1050, and 660 cm −1 are generated by C C stretching vibration, C O C stretching of pyranose ring, and C OH out of plane bending mode. The appearance of the foregoing bands of native CL in spectra of APS-CNPs confirm that, using APS agent has not deterioration effect on chemical structure of CL This observation is in agreement with that found by other researchers, 62,66 but on other cellulosic materials rather than native CL.…”

“…It is interesting to note that, our CNPs obtained by APS agent superior that obtained by other literatures reported oxidation methods, for example, permanganate oxidation, TMPO, and APS with other oxidation conditions. 50,52,[62][63][64][65]…”