Pyridinium-grafted-cellulose nanocrystals were prepared by a simple one-pot reaction using 4-(1-bromoethyl/bromomethyl)benzoic acid, pyridine and cellulose nanocrystals (CNCs). The grafting consists of an esterification reaction between 4-(1-bromoethyl/bromomethyl)benzoic acid and CNCs and a nucleophilic attack on the C-Br bond of 4-(1-bromoethyl/bromomethyl)benzoic acid by pyridine. This reaction simplifies existing cationization methods, which leads to a higher grafting density while retaining the CNC crystallinity.

Flexible composite films with a high cellulose nanowhisker (CNW) content of up to 75% by weight were produced by casting from aqueous solution with water soluble cellosize (CS). The surface topography of the films displayed an aggregated morphology influencing the surface roughness and light transparency properties of the blends. Using fluorescently labelled CS, we were able to determine the extent of aggregation in the composites which indicated that up to 13% of CNWs can be homogeneously blended with CS, above which larger CNW aggregates occur. However, even in a somewhat aggregated form, the CNWs still form a percolated network and appear to be homogeneously dispersed as larger aggregated entities. The composite CNW-CS films further exhibited improved thermal stability compared to both the CNWs and CS alone with decomposition temperatures shifting from 261 C for CNWs and 313 C for CS to 361 C for blends containing 75% CNWs. Surface induced crystallisation of CS by CNWs was also found with higher crystallinity for the composite films than for the individual constituents. Due to the reinforcing effect of CNWs within the matrix, an increase in the tensile strength (294%) and modulus (2004%) was observed for the blend containing 75% CNWs compared to the pure CS film (tensile strength $12.23 MPa and modulus $0.39 GPa). The storage modulus of all the flexible blends/films investigated also revealed an increasing trend with the CNW content across the temperature region explored. The swelling kinetics of the CNW-CS blends in phosphate buffered saline (PBS) media at 37 C were also investigated and CNWs were shown to have a strong influence on reducing the equilibrium swelling capacity and initial swelling rate of the blends.

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This article reports on the successful preparation and characterization of cellulose nanocrystals (CNCs) surface-modified with polylactide (PLA) and poly­(butylene succinate) (PBS) binary mixed homopolymer brushes. Their synthesis was designed as a three-step procedure combining polyester synthesis and surface-modification of CNCs with simultaneous polyester grafting via a heterogeneous copper­(I)-catalyzed azide–alkyne cycloaddition reaction. For comparison, single homopolymer brushes tethered to CNCs (PLLA-g-CNC and PBSBDEMPAM-g-CNC) were obtained applying the same procedure. The hairy nanoparticles were characterized in terms of chemical composition and thermal properties. Spectroscopic analyses suggested “rippled” microphase separation of both immiscible homopolyesters in the mixed brushes, while others showed impeded homopolyester crystallization after surface-grafting. A synergistic relationship between the polyesters and CNCs was also suggested, i.e., the polyester grafting increases the CNC thermal resistance, while CNC presence imparts char formation. The as-obtained binary homopolymer brushes tethered to nanoparticles makes these surface-modified cellulosic nanomaterials attractive as compatibilization/reinforcement agents for PLA/PBS blends.

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A new cellulose nanocrystal–reduced graphene oxide (CNC–rGO) nanocomposite was successfully used for mediatorless electrochemical sensing of methyl paraben (MP). Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) studies confirmed the formation of the CNC–rGO nanocomposite. Cyclic voltammetry (CV) studies of the nanocomposite showed quasi-reversible redox behavior. Differential pulse voltammetry (DPV) was employed for the sensor optimization. Under optimized conditions, the sensor demonstrated a linear calibration curve in the range of 2 × 10−4–9 × 10−4 M with a limit of detection (LOD) of 1 × 10−4 M. The MP sensor showed good reproducibility with a relative standard deviation (RSD) of about 8.20%. The sensor also exhibited good stability and repeatability toward MP determinations. Analysis of MP in cream samples showed recovery percentages between 83% and 106%. Advantages of this sensor are the possibility for the determination of higher concentrations of MP when compared with most other reported sensors for MP. The CNC–rGO nanocomposite-based sensor also depicted good reproducibility and reusability compared to the rGO-based sensor. Furthermore, the CNC–rGO nanocomposite sensor showed good selectivity toward MP with little interference from easily oxidizable species such as ascorbic acid.

Inspired by nature, cellulose extracted from plant wastes has been explored, due to its great potential as an alternative for synthetic fiber and filler that contributes to structural performance. The drive of this study was to extract, treat, and evaluate the characteristics of rice straw (RS) (Oryza sativa L.) cellulose as a biodegradable reinforcement to be utilized in polymer base materials. Two routes of extraction and treatment were performed via the pulping (Route 1) and chemo-mechanical methods (Route 2), in order to discover comparative characteristics of the synthesized cellulose fiber. Comprehensive characterization of RS cellulose was carried out to determine crystallinity, surface morphology, and chemical bonding properties, using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infra-red (FTIR), respectively. The XRD test results showed that the crystallinity index (CI) of cellulose powder (CP) decreased after the surface modification treatment, Route 2, from 64.50 to 50.10% CI for modified cellulose powder (MCP), due to the surface alteration of cellulose structure. From Route 1, the crystallinity of the fibers decreased up to 33.5% (dissolve cellulose, DC) after the pulp went through the surface modification and dissolution processes, resulting from the transformation of cellulose phase into para-crystalline structure. FESEM micrographs displayed a significant reduction of raw RS diameter from 7.78 µm to 3.34 µm (treated by Route 1) and 1.06 µm (treated by Route 2). The extracted and treated cellulose via both routes, which was considerably dominated by cellulose II because of the high percentage of alkaline used, include the dissolve cellulose (DC). The dissolution process, using NMMO solvent, was performed on the pulp fiber produced by Route 1. The fiber change from cellulose I to cellulose II after undergoes the process. Thus, the dissolution process maintains cellulose II but turned the pulp to the cellulose solution. The acquired characteristics of cellulose from RS waste, extracted by the employed methods, have a considerably greater potential for further application in numerous industries. It was concluded that the great achievement of extracted RS is obtained the nanosized fibers after surface modification treatment, which is very useful for filler in structural composite applications.