Enhancing the mechanical properties of hydrogels with vinyl-functionalized nanocrystalline cellulose as a green crosslinker

Hydrogels have gained significant attention in scientific communities for their versatile applications, but several challenges need to be addressed to exploit their potential fully. Conventional hydrogels suffer from poor mechanical strength, limiting their use in many applications. Moreover, the crosslinking agents used to produce them are often toxic, carcinogenic, and not bio-friendly. This study presents a novel approach to overcome these limitations by using bio-friendly modified nanocrystalline cellulose as a crosslinker to prepare highly stretchable and tough thermosensitive hydrogels. The surface of nanocrystalline cellulose was modified with 3-methacryloxypropyltrimethoxysilane (MPTS) to obtain modified nanocrystalline cellulose (M-NCC) crosslinker and used during free radical polymerization of thermosensitiveN-isopropyl acrylamide (NIPA) monomer to synthesize NIPA/M-NCC hydrogel. The resulting nanocomposite hydrogels exhibit superior mechanical, thermal, and temperature-responsive swelling properties compared to conventional hydrogels prepared with traditional bi-functionalN,N'-methylene bis (acrylamide) (MBA) as a crosslinker. The elongation at break, tensile strength, and toughness of the NIPA/M-NCC hydrogels significantly increase and Young's modulus decrease than conventional hydrogel. The designed M-NCC crosslinker could be utilized to improve the mechanical strength of any polymeric elastomer or hydrogel systems produced through chain polymerization.

Hydrophobicity and corrosion resistance of waterborne fluorinated acrylate/silica nanocomposite coatings

This study aims to improve the hydrophobic properties and corrosion resistance of fluorinated acrylate coatings. The surface of nano-SiO2 was modified by the silicone coupling reagent (KH-570), and the reactive functional groups were introduced to modify fluorinated acrylates. The functionalized SiO2-modified waterborne fluorinated acrylate emulsion was prepared by free polymerization with dual initiators. The structure of the polymer was analyzed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectro-meter (1H-NMR), X-ray photoelectron spectroscopy (XPS) and Waters gel chromatography (GPC). The properties of the films and coatings were analyzed by contact angle, atomic force microscopy, scanning electron microscopy, and electrochemical analysis. The results showed that the contact angle reached 120° when the SiO2 content was 3%, the electrochemical impedance value reached 1.49 × 107 Ω·cm2, and the pencil hardness was 3H.

Enhanced electrophoretic separation of proteins by tethered SiO2 nanoparticles in an SDS-polyacrylamide gel network

Nanoparticles (NPs) are able to improve the separation efficiency of proteins in SDS-polyacrylamide gel electrophoresis (SDS-PAGE) due to their capability of enhancing heat dissipation during electrophoresis. However, the intrinsic surface charges of NPs (at buffer pH or charge induced due to the SDS coating) make them acquire electrophoretic mobility and movement in the gel. Such a movement leads to viscosity and temperature gradients in the gel and deteriorates the separation. In this work, we proposed a novel method by using tethered NPs in the gel. Silica NPs, as the model NPs, were prepared and their surfaces were modified using 3-[(methacryloxy)propyl] trimethoxysilane (MPS) which locks the NPs in the gel via covalent bonds (M-SiO₂/PA (polyacrylamide)). SiO₂ NPs were embedded into the gel (SiO₂/PA) as the positive control, while pure PA gel was chosen as the negative control. The results showed that at a relatively high voltage of 250 V, although the Joule heat generated during electrophoresis disturbed the separation in the pure gel, the SiO₂/PA and M-SiO₂/PA nanocomposite gels showed better performances. In comparison with the pure PA gel, the resolution increased by 3 and 32% for SiO₂/PA and M-SiO₂/PA, respectively, in a relatively short separation time of 35 min. The gel with tethered NPs presented a more efficient separation in terms of band broadening and resolution compared with the gel with free NPs probably due to the movement of free charged particles in the gel. Evidently, the migration speed of protein bands in the gels decreased especially for larger proteins in the presence of the NPs compared to the pristine gel due to the steric hindrance of the NPs. Finally, we separated E. coli proteins, as a real sample. Among the three gels (pure PA, SiO₂/PA, and M-SiO₂/PA), the gel containing M-SiO₂ showed the best performance.

The synthesis of monodispersed M-CeO2/SiO2nanoparticles and formation of UV absorption coatings with them

CeO₂/polymer nanoparticles have drawn considerable attention for their excellent UV absorption properties. However, many challenges still exist in the successful incorporation of ceria into the polymer matrix for the easy agglomeration and photocatalytic activity of CeO₂ nanoparticles. Herein, we address these issues by constructing three-layer structured nanoparticles (M-CeO₂@SiO₂) and incorporating them into a polymer matrix through a mini-emulsion polymerization process. During this process, small-sized nano-ceria became uniformly anchored on the surfaces of monodisperse silica particles first, and then the particles were coated with an MPS/SiO₂ shield. The morphology and dispersion of the nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The performance of the hybrid films was characterized using UV-vis absorption spectroscopy (UV-vis) and water contact angle (WCA) measurements. Results showed that the M-CeO₂@SiO₂ nanoparticles exhibited a three-layer structure with a mean diameter of 360 nm, and they possess good compatibility with acrylic monomers. After the addition of M-CeO₂@SiO₂, hybrid films exhibited enhanced UV absorption capacity as expected, accompanied by an obvious improvement in hydrophobicity (the water contact angle increased from 84.2° to 98.2°). The results showed that the hybrid films containing M-CeO₂@SiO₂ particles possess better global performance as compared with those containing no particles.

Herein, we report the synthesis of monodispersed M-CeO₂/SiO₂ nanoparticles and their use in the construction of a UV absorption coating.

Aerosol-assisted chemical vapour deposition of transparent superhydrophobic film by using mixed functional alkoxysilanes

A method for the preparation of transparent superhydrophobic silica coatings on glass substrates via aerosol-assisted chemical vapour deposition (AACVD) is described. A multi-layer process to produce dual scale silica nanoparticles films, by using different functional alkoxysilanes was investigated. A first layer of 3-methacryloxypropyltrimethoxysilane (MPS) and a second layer of tetraethylorthosilicate (TEOS) were deposited at different temperatures to generate micro and nano particles of silica. Finally, a layer of perfluorooctyltriethoxysilane was deposited on top of the two layers to achieve superhydrophobicity. The transparent superhydrophobic film showed transparency of 90% in the visible light region with a static water contact angle of 165° and a sliding angle lower than 1°. Various durability tests were performed on the transparent superhydrophobic film, showing a constant water repellency after corrosion and organic solvents tests, strong resistance under UV light, and thermal stability up to 400 °C. Sandpaper mechanical robustness durability test showed superhydrophobicity for up to 5 rubbing cycles. In this study, a novel strategy to achieve highly transparent superhydrophobic glass surfaces using AACVD of alkoxysilanes, to produce surfaces with excellent durability is described. This shows great potential to obtain silica superhydrophobic films for large-scale applications.