The Effect of Cellulose Nanocrystal Suspension Treatment on Suspension Viscosity and Casted Film Property

DES-ultrasonication treatment of cellulose nanocrystals and the reinforcement in carrageenan biocomposite

CNCs are intensively studied to reinforce biocomposites. However, it remains a challenge to homogeneously disperse the CNC in biocomposites for a smooth film surface. Mechanochemical treatment via ultrasonication in deep eutectic solvent (DES) generated a stable dispersion of CNC before incorporation into carrageenan biocomposite. Shifted peaks of choline chloride (ChCl) methylene groups to 3.95-3.98 ppm in 1H NMR indicated a formation of eutectic mixture between the hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) at the functional group of CH3···OH. The swelling of CNC in the DES was proven by the formation of intermolecular H-bond at a length of 2.46 Å. The use of DES contributed to a good dispersion of CNC in the solution which increased zeta potential by 43.2 % compared to CNC in deionized water. The ultrasonication amplitude and feed concentration were varied for the best parameters of a stable dispersion of CNC. The crystallinity of 1 wt% of CNC at 20 % sonication amplitude improved from 76 to 81 %. The high crystallinity of CNCDES resulted in an increase in film tensile and capsule loop strength of Carra-CNCDES by 20.7 and 19.4 %, respectively. Improved dispersion of CNCDES reduced the surface roughness of the biocomposite by 21.8 %. H-bond network in CNCDES improved the biocomposite properties for an ingenious reinforcement material.

Modified cellulose nanocrystals enhanced polycaprolactone multifunctional films with barrier, UV-blocking and antimicrobial properties for food packaging

The packaging industry demands improved eco-friendly materials with new and enhanced properties. In this context, bio-nanocomposite films with antimicrobial and UV-shielding properties based on modified cellulose nanocrystals/polycaprolactone (MCNC/PCL) were fabricated via solution casting method, and then food packaging simulation was carried out. CNCs were obtained by acid hydrolysis followed by successful functionalization with Quaternary ammonium surfactant, confirmed by FTIR, XPS, XRD, TEM, and DLS analyses. Furthermore, the morphological, physical, antibacterial, and food packaging properties of all prepared films were investigated. Results showed that the mechanical, UV blocking, barrier properties, and antibacterial activity of all composite films were remarkably improved. Particularly, the addition of 3 wt% MCNC increased the tensile strength and elongation at break by 27.5 % and 20.0 %, respectively. Moreover, the permeability of O2, CO2, and water vapor dramatically reduced by 97.6 %, 96.7 %, and 49.8% compared to the Neat PCL. Further, the UV-blocking properties of the composite films were significantly improved. The antimicrobial properties of MCNC/PCL films showed good antimicrobial properties against S. aureus. Finally, cherry packaged with 1 and 3 wt% MCNC films exhibited satisfactory freshness after 22 days of preservation. Overall, the fabricated PCL nanocomposite films can be utilized in the food packaging industry.

Structural Color from Cellulose Nanocrystals or Chitin Nanocrystals: Self-Assembly, Optics, and Applications

Widespread concerns over the impact of human activity on the environment have resulted in a desire to replace artificial functional materials with naturally derived alternatives. As such, polysaccharides are drawing increasing attention due to offering a renewable, biodegradable, and biocompatible feedstock for functional nanomaterials. In particular, nanocrystals of cellulose and chitin have emerged as versatile and sustainable building blocks for diverse applications, ranging from mechanical reinforcement to structural coloration. Much of this interest arises from the tendency of these colloidally stable nanoparticles to self-organize in water into a lyotropic cholesteric liquid crystal, which can be readily manipulated in terms of its periodicity, structure, and geometry. Importantly, this helicoidal ordering can be retained into the solid-state, offering an accessible route to complex nanostructured films, coatings, and particles. In this review, the process of forming iridescent, structurally colored films from suspensions of cellulose nanocrystals (CNCs) is summarized and the mechanisms underlying the chemical and physical phenomena at each stage in the process explored. Analogy is then drawn with chitin nanocrystals (ChNCs), allowing for key differences to be critically assessed and strategies toward structural coloration to be presented. Importantly, the progress toward translating this technology from academia to industry is summarized, with unresolved scientific and technical questions put forward as challenges to the community.

Response surface optimization of process parameters for preparation of cellulose nanocrystal stabilized nanosulphur suspension

This study employed response surface methodology (RSM) to optimize various parameters involved in the synthesis of nanosulphur (NS) stabilized by cellulose nanocrystals (CNCs). The elemental sulphur (ES) mixed with CNCs was processed in a high-pressure homogenizer to make a stable formulation of CNC-stabilized NS (CNC-NS). RSM was adopted to formulate the experiments using Box-Behnken design (BBD) by considering three independent variables i.e., ES (5, 10, 15 g), CNCs (25, 50, 75 ml), and the number of passes (NP) in the high-pressure homogenizer (1, 2, 3). For the prepared suspensions (CNC-NS), the range of the responses viz. settling time (0.84-20.60 min), particle size (500.41-1432.62 nm), viscosity (29.20-420.60 cP), and surface tension (60.35-73.61 N/m) were observed. The numerical optimization technique was followed by keeping the independent and dependent factors in the range yielded in the optimized solution viz. 46 ml (CNCs), 8 g (ES), and 2 (NP). It was interpreted from the findings that the stability of the suspension had a positive correlation with the amount of CNC while the increasing proportion of ES resulted in reduced stability. The quadratic model was fitted adequately to all the responses as justified with the higher coefficient of determination (R2 ≥ 0.88). The characterization performed by X-ray diffraction (XRD), zeta potential, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) revealed better-stabilizing properties of the optimized CNCs-ES suspension. The study confirmed that CNCs have the potential to be utilized as a stabilizing agent in synthesizing stable nanosulphur formulation by high-pressure homogenization.

Polyanionic electrically conductive superabsorbent hydrogel based on sodium alginate-g-poly (AM-co-ECA-co-AMPS): Broadband dielectric spectroscopy investigations

In this study, the dielectric behavior of polyanionic electrically conductive superabsorbent hydrogel based on sodium alginate-g-poly(AM-co-ECA-co-AMPS) was investigated by broadband dielectric spectroscopy (BDS). The dielectric spectra obtained from -70 to 70 °C showed a superposition of three distinctive processes, electrode polarization, charge carrier's transport, and a molecular relaxation process. These dynamic processes were further analyzed along with the effect of both temperature and reduced graphene oxide (rGO) content. The development of a clear electrochemical double layer (ECDL) at the electrode/hydrogel interface strongly supports its possible application in supercapacitors' forms of energy storage. TGA, DSC, rheology, and electrochemical properties were studied. Furthermore, when the composite hydrogel with rGO content of 2.5 % was assembled into a symmetric supercapacitor, it displayed a specific capacitance of 756 F.g^-1 at 1 A.g^-1 and 704 F.g^-1 after 5000 cycles with high capacitance retention of 93.2 %. The superior conductivity and porous structure of the rGO composite hydrogel are credited with the hydrogel's excellent electrochemical capabilities.

Nanocellulose-Based Nanocomposites for Sustainable Applications: A Review

Nanocellulose has emerged in recent years as one of the most notable green materials available due to its numerous appealing factors, including its non-toxic nature, biodegradability, high aspect ratio, superior mechanical capabilities, remarkable optical properties, anisotropic shape, high mechanical strength, excellent biocompatibility and tailorable surface chemistry. It is proving to be a promising material in a range of applications pertinent to the material engineering to biomedical applications. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations. This review presents an overview of general concepts in nanocellulose-based nanocomposites for sustainable applications. Beginning with a brief introduction of cellulose, nanocellulose sources, structural characteristics and the extraction process for those new to the area, we go on to more in-depth content. Following that, the research on techniques used to modify the surface properties of nanocellulose by functionalizing surface hydroxyl groups to impart desirable hydrophilic-hydrophobic balance, as well as their characteristics and functionalization strategies, were explained. The usage of nanocellulose in nanocomposites in versatile fields, as well as novel and foreseen markets of nanocellulose products, are also discussed. Finally, the difficulties, challenges and prospects of materials based on nanocellulose are then discussed in the last section for readers searching for future high-end eco-friendly functional materials.

Aqueous Dispersion of Carbon Nanomaterials with Cellulose Nanocrystals: An Investigation of Molecular Interactions

Dispersing carbon nanomaterials in solvents is effective in transferring their significant mechanical and functional properties to polymers and nanocomposites. However, poor dispersion of carbon nanomaterials impedes exploiting their full potential in nanocomposites. Cellulose nanocrystals (CNCs) are promising for dispersing and stabilizing pristine carbon nanotubes (pCNTs) and graphene nanoplatelets (pGnP) in protic media without functionalization. Here, the underlying mechanisms at the molecular level are investigated between CNC and pCNT/pGnP that stabilize their dispersion in polar solvents. Based on the spectroscopy and microscopy characterization of CNCpCNT/pGnP and density functional theory (DFT) calculations, an additional intermolecular mechanism is proposed between CNC and pCNT/pGnP that forms carbonoxygen covalent bonds between hydroxyl end groups of CNCs and the defected sites of pCNTs/pGnPs preventing re-agglomeration in polar solvents. This work's findings indicate that the CNC-assisted process enables new capabilities in harnessing nanostructures at the molecular level and tailoring the performance of nanocomposites at higher length scales.

Effect of oxalic acid and sulphuric acid hydrolysis on the preparation and properties of pineapple pomace derived cellulose nanofibers and nanopapers

Nanocellulose is the "green magnet" which attracts a wide spectrum of industries towards it due to its availability, biodegradability, and possible smart applications. For the first time, pineapple pomace was being explored as an economic precursor for cellulose nanofibers. Nanofiber isolation was accomplished using a chemo-mechanical method and solution casting was adopted for the development of nanopapers. Moreover, the study examines the structural, optical, crystalline, dimensional, and thermal features of nanofibers isolated using different acid hydrolysis (oxalic acid and sulphuric acid) methods. Fourier-transform infra-red spectroscopy, ¹³C solid-state nuclear magnetic resonance spectroscopy, and X-ray diffraction analysis indicated the presence of type I cellulose. The transmittance, crystallinity index, and thermal stability of PPNFS (sulphuric acid treated fiber) were greater than PPNFO (oxalic acid treated fiber). The transmission electron microscopy and dynamic light scattering analysis confirmed the nanodimension of PPNFO and PPNFS. While comparing the optical and mechanical properties of nanopapers, PPNFS outperforms PPNFO. The tensile strength of the prepared nanopapers (64 MPa (PPNFO) and 68 MPa (PPNFS)) was found to be high compared to similar works reported in the literature. The prepared nanopaper is proposed to be used for food packaging applications.

Hybrid Films Prepared from a Combination of Electrospinning and Casting for Offering a Dual-Phase Drug Release

One of the most important trends in developments in electrospinning is to combine itself with traditional materials production and transformation methods to take advantage of the unique properties of nanofibers. In this research, the single-fluid blending electrospinning process was combined with the casting film method to fabricate a medicated double-layer hybrid to provide a dual-phase drug controlled release profile, with ibuprofen (IBU) as a common model of a poorly water-soluble drug and ethyl cellulose (EC) and polyvinylpyrrolidone (PVP) K60 as the polymeric excipients. Electrospun medicated IBU-PVP nanofibers (F7), casting IBU-EC films (F8) and the double-layer hybrid films (DHFs, F9) with one layer of electrospun nanofibers containing IBU and PVP and the other layer of casting films containing IBU, EC and PVP, were prepared successfully. The SEM assessments demonstrated that F7 were in linear morphologies without beads or spindles, F8 were solid films, and F9 were composed of one porous fibrous layer and one solid layer. XRD and FTIR results verified that both EC and PVP were compatible with IBU. In vitro dissolution tests indicated that F7 were able to provide a pulsatile IBU release, F8 offered a typical drug sustained release, whereas F9 were able to exhibit a dual-phase controlled release with 40.3 ± 5.1% in the first phase for a pulsatile manner and the residues were released in an extended manner in the second phase. The DHFs from a combination of electrospinning and the casting method pave a new way for developing novel functional materials.