Qilin Lu

Ultrasonication-assisted manufacture of cellulose nanocrystals esterified with acetic acid

Esterified cellulose nanocrystals (E-CNCs) are cellulose derivatives that could be applied in biomedical and chemical industries. E-CNCs were prepared with cellulose pulp using a mixture of 17.5M acetic and 18.4M sulfuric acid with the aid of ultrasonication. The effects of esterification time (3-7h), ultrasonication time (with a frequency of 40 kHz, 0 to 6h) and temperature (68-75 °C) on the yield and degree of substitution (DS) of E-CNCs were evaluated. The sample obtained without ultrasonication had the lowest yield and DS value of 48.16% and 0.22, respectively, whereas ultrasonication for 5h at 70 °C resulted in a yield of 85.38% and a DS value of 0.46. Characterization indicated the successful esterification of hydroxyl groups of cellulose, and the width of rod-shaped E-CNCs was from 10 to 100 nm. The study provides a simple and convenient method to manufacture E-CNCs.

Preparation, characterization and optimization of nanocellulose whiskers by simultaneously ultrasonic wave and microwave assisted.

Simultaneously ultrasonic wave and microwave assisted technique (SUMAT), as a method of process intensification, was first applied to the preparation of nanocellulose whiskers (NCWs) from filter paper by sulfuric acid hydrolysis. The effects of temperature, sulfuric acid concentration, and mass of raw material and time on the yield of NCWs were investigated by single-factor experiments, and the preparation conditions were optimized with response surface methodology. The obtained NCWs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermal gravimetry. The results showed NCWs were facilely prepared by using SUMAT. However, some harsh reaction conditions such as high temperature, strong acidity and long time treatment easily induced the reduction of the yield of NCWs. Under the optimal conditions, the yield and the crystallinity of NCWs with the crystal form of cellulose Iα is 85.75% and 80%, respectively.

Organic solvent-free and efficient manufacture of functionalized cellulose nanocrystals via one-pot tandem reactions

An environmentally benign approach for the manufacture of maleic anhydride functionalized cellulose nanocrystals (MA-CNCs) via one-pot tandem reactions with H2SO4 as a catalyst under organic solvent-free conditions was put forward. The effects of ball milling time, ultrasonication temperature and time on the yield and degree of substitution (DS) have been explored.

Bi(OTf)3-catalyzed C–H bond functionalization of azaarenes for the facile access to oxindoles featuring quaternary carbon centers

The direct sp3 C–H bond functionalization of 2-alkyl azaarenes to isatylidene malononitriles has been achieved using Bi(OTf)3 as the catalyst, resulting in a series of oxindoles containing an all-carbon quaternary center in moderate to good yields. This protocol provided an efficient and convenient method for the construction of potentially useful azaarene substituted oxindoles.

One-pot tandem reactions for the preparation of esterified cellulose nanocrystals with 4-dimethylaminopyridine as a catalyst

An efficient approach for the manufacture of esterified cellulose nanocrystals (E-CNCs) via one-pot tandem reactions with 4-dimethylaminopyridine (DMAP) as a catalyst under mild operating conditions is put forward. The effects of ball milling time, reaction temperature and ultrasonication time on the yield and degree of substitution (DS) are explored. Characterization indicates the successful esterification of the hydroxyl groups of cellulose. The micromorphology and microstructure of the prepared E-CNCs are studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that the E-CNCs are short rod-like particles 130–230 nm in length and 20–40 nm in width, forming an interconnected network structure. X-ray diffraction (XRD) results indicate that the crystallinity index increases from 63.5% to 77.2%. The thermal properties of the E-CNCs are investigated by thermogravimetric analysis (TGA) and the results show that the E-CNCs exhibit higher thermal stability than cellulose pulp.

Development of organic–inorganic hybrid beads from sepiolite and cellulose for effective adsorption of malachite green

Organic–inorganic hybrid adsorbents based on sepiolite and cellulose were prepared through an easy-to-handle procedure. Hydrogen-bonding existed between the silanol groups (Si–OH) on the sepiolite surface and the hydroxyl groups of the cellulose structure resulting in the formation of hybrid beads with good synergistic effects. Incorporation of the inorganic molecule sepiolite into the renewable polymer cellulose opened an opportunity for the development of alternative environment-friendly adsorbents with improved adsorption efficiency as well as enhanced thermal stability compared with neat cellulose beads. The utility of the obtained sepiolite/cellulose beads was demonstrated by investigating their performance for the removal of malachite green (MG). The maximum adsorption capacity of MG on sepiolite/cellulose beads was close to the calculated results from the Langmuir adsorption isotherm, and the adsorption kinetics followed well to the pseudo-second-order model.

One-pot construction of cellulose-gelatin supramolecular hydrogels with high strength and pH-responsive properties

Inspired by the supramolecular structure of cellulose, cellulose-gelatin supramolecular hydrogels with high strength and pH-sensitivity were constructed in a basic-based solvent system, ethylene diamine/potassium thiocyanate (EDA/KSCN) with the aid of cyclic freezing-thawing. The investigation on the characteristics of supramolecular hydrogels revealed that repeated freezing-thawing cycles played an important role in the formation of the physical cross-linked supramolecular network structure between cellulose and gelatin. The mechanical properties of supramolecular hydrogels were much higher than pure cellulose and gelatin hydrogel, and the compressive strength was 9.6 times higher than that of pure gelatin hydrogel. The synergistic effect between hydrogen-bonding interaction and the reinforcement of regenerated cellulose nanofibrils (CNF) contributed to the superior mechanical performance. Furthermore, the swelling kinetics tests showed that the supramolecular hydrogels exhibited excellent pH-responsibility, indicating potential applications in biomedical fields. Thus, a straightforward route to construct natural polymer-based hydrogels with supramolecular structure through physical crosslinking strategy without employing hazardous crosslinking agents was developed, paving the way for the design of new types of hydrogels.