Despite the growing interest in polydiacetylene (PCDA)-based materials in recent years due to their thermal-stimuli responsive discoloration characteristics, it is still a huge challenge to fabricate ...high-performance and environment-friendly thermochromic materials. In this work, we demonstrated ultrastrong thermochromic materials based on 1,6-Diaminohexane (DH) crosslinked 2,2,6,6-tetramethylpiperidine-1-oxylradi-cal (TEMPO)-oxidized nanofibrillated cellulose (TNFC) matrix and poly-PCDA chains through a vacuum-assisted filtration assembly technique. The synergistic interactions of covalent cross-linking networks efficiently prevented crack propagation under loading, endowed the resulting TNFC-polyPCDA-DH nanocomposites with super high tensile strength of 281.63 ± 5.63 MPa and Young's modulus of 13.68 ± 1.09 GPa. Moreover, the resultant nanocomposites exhibited a rapidly reversible thermal discoloration (up to 140 °C), and excellent thermal reversible cycling performance. This strategy offers a promising approach to design and prepare flexible high-performance intelligent nanocomposite, which may be widely applied in wearable sensors, displays, and anti-counterfeiting labels.
An ultrastrong, reversible thermochromic biomass-based film is fabricated with the synergistic effect of the short and long covalent-crosslinking networks via a simple vacuum-assisted filtration assembly technique. Display omitted
•A thermochromic film is constructed with the synergistic effect of the short and long covalent-crosslinking networks.•The thermochromic film has excellent mechanical properties.•The high-performance thermochromic material exhibits fascinating reversible thermochromism performance and outstanding reversible cycle property.
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•Aqueous Laponite/TEMPO-NFC dispersions are studied under shear conditions.•Flow and oscillatory tests show synergistic effects of clay-polymer blending.•Positive synergistic effects ...are particularly important for Laponite poor blends.•Essential role is played by electrostatic interaction between fibrils and nanodisks.•Laponite act as bridging agent between nanocellulose fibrils.
The viscoelastic and flow properties of aqueous Laponite/TEMPO-oxidized nanofibrillated cellulose (TEMPO-NFC) systems are investigated with the aim to study the effect of content and proportion of both components on the properties. Both Laponite and TEMPO-NFC aqueous dispersions can find numerous applications in different fields (from industrial to biomedical one) due to their structural and rheological properties. The most important effects of blending are observed at low Laponite fractions, also with qualitative changes in the shape of the flow curves and mechanical spectra. Positive synergistic effects are ascribed to the interpenetration and electrostatic interactions between TEMPO-NFC fibrils and Laponite nanodisks. These mechanisms are more effective in Laponite-poor blends when a minority of clay nanoparticles and its aggregated forms are distributed within the nanocellulose matrix, acting as bridging agents between polymer nanofibrils. The synergistic effects are compared to those observed for Laponite blends with a nonionic biopolymer, scleroglucan.
Here we describe the synthesis and characterization of a peptide-cellulose conjugate biosensor based on TEMPO-oxidized nanofibrillated cellulose (tNFC) for detecting elevated levels of human ...neutrophil elastase (HNE) in chronic wounds. The fluorescent peptide HNE substrate constructed from n-succinyl-Ala-Pro-Ala-7-amino-4-methyl-coumarin was attached to the TEMPO-oxidized cellulose surface via polyethylene glycol linker. The characterization of the biosensor conjugate shows a high degree of peptide incorporation onto the surface with the degree of substitution of 0.057. The relatively small crystallite size of 26.0 Å compared to other cellulose- and nanocellulose-based materials leads to a large specific surface area which can promote access of HNE to the enzyme substrates due to decreased steric interactions. Likewise, the porosity for tNFC was found to be higher than all other samples, including the nanocellulosic aerogel, lending to its hydrogel-like nature. The properties of tNFC were compared to other cellulose-based materials. The volume of each crystallite and volume ratio to the largest sample was calculated. tNFC was found to occupy the smallest space resulting in high amounts of sensors per crystallite unit volume. With a small crystallite volume and large number of sensors, the tNFC peptide-cellulose conjugate biosensor could provide a more sensitive system and is a good candidate for point of care diagnostic devices for detecting elevated protease levels in humans.
Peptide-cellulose conjugates designed for use as optical protease sensors have gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with ...chronic illnesses, necessitating optimal biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Here, we examine a tripeptide, fluorogenic elastase biosensor attached to TEMPO-oxidized nanofibrillated cellulose via a polyethylene glycol linker. The synthetic conjugate was found to be active in the presence of human neutrophil elastase at levels comparable to other cellulose-based biosensors. Computational models examined the relationship of the sensor molecule to the transducer surface. The results illustrate differences in two crystallite transducer surfaces ((110) vs. (1-10)) and reveal preferred orientations of the sensor. Finally, a determination of the relative (110) vs. (1-10) orientations of crystals extracted from cotton demonstrates a preference for the (1-10) conformer. This model study potentiates the HNE sensor results for enhanced sensor activity design.
Soybean protein isolate (SPI) is well-suited to the preparation of composite films due to its abundance, renewability, biodegradability, and favorable film-forming capacity. In this study, different ...SPI-based composite films were prepared by incorporating nano-ZnO and 2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO) oxidized nanofibrillated cellulose (TNFC) separately or together. Nano-ZnO was introduced to endow the films with multifunction capability, while TNFC was introduced to stabilize the nanoparticles. Both the macro optical characterization and micro scanning electron microscope with energy dispersive X-ray (SEM–EDX) analysis indicated that TNFC could significantly decrease nano-ZnO aggregation and improve its dispersibility in the SPI matrix due to the mechanical restriction and physical adsorption effect of TNFC to the nano-ZnO. In addition to the improved dispersibility, incorporating nano-ZnO and TNFC benefitted the mechanical properties and thermo stability of the SPI-based composite films. The tensile strength and Young’s modulus increased by 73 and 57%, respectively, and the maximum degradation temperature increased by 10 °C, compared to that of the unmodified SPI film. These results can be attributed to the hydrogen bonds formed among SPI components, TNFC, and nano-ZnO, which were further examined by attenuated total reflectance-fourier transform infrared spectroscopy and X-ray diffraction analysis. After the incorporation of nano-ZnO, the SPI-based composite films also possessed excellent UV-shielding capacity and superior antimicrobial ability. To this effect, this work provides a valuable reference for nanoparticles dispersion and application in regards to polymer enhancement and multi-functionalization.
This research explores fundamental, structural differences of ultrathin films, prepared with three distinct deposition methods using 2,2,6,6-tetramethyl-piperidin-1-oxyl radical oxidized cellulose ...nanofibres (TEMPO-CNFs) derived from never dried bleached birch pulp. There is standard characterization by atomic force microscopy (morphology, roughness) and ellipsometry (thickness) and important structural data is gained by exposing the films to water vapor and monitoring the vapor uptake with quartz crystal microbalance (QCM). Significant distinctions were found from QCM data that could be linked to the structure of the films, originating from the three deposition methods: adsorption, spin coating and electrophoretic deposition. Moreover, the results shown here have potential implications for various types of films that comprise of amphiphilic nanomaterials that have a distinct response to moisture or aqueous based solutions.
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