Hydrophobic Cellulose Research Articles

Highly transparent, hydrophobic, and durable anisotropic cellulose films as electronic screen protectors

Cellulose films have attracted extensive interest in the field of burgeoning electronic devices. However, it remains a challenge to simultaneously address the difficulties including facile methodology, hydrophobicity, optical transparency, and mechanical robustness. Herein, we reported a coating-annealing approach to fabricate highly transparent, hydrophobic, and durable anisotropic cellulose films, where poly(methyl methacrylate)-b-poly(trifluoroethyl methacrylate) (PMMA-b-PTFEMA) as low surface energy chemicals was coated onto regenerated cellulose films via physical (hydrogen bonds) and chemical (transesterification) interactions. The resultant films with nano-protrusions and low surface roughness exhibited high optical transparency (92.3 %, 550 nm) and good hydrophobicity. Moreover, the tensile strength of the hydrophobic films was 198.7 MPa and 124 MPa in dry and wet states, respectively, which also showed excellent stability and durability under various conditions, such as hot water, chemicals, liquid foods, tape peeling, finger pressing, sandpaper abrasion, ultrasonic treatment, and water jet. This work provided a promising large-scale production strategy for the preparation of transparent and hydrophobic cellulose-based films for electronic device protection as well as other emerging flexible electronics.

A facile strategy to fabricate antibacterial hydrophobic, high-barrier, cellulose papersheets for food packaging

As a traditionally used packaging material, natural cellulose-based paper has poor barrier properties to water and oxygen, which severely limits its wide application in food packaging. In this study, we report a new sustainable approach to producing hydrophobic, high-barrier, and antibacterial packaging materials from cellulose paper. In this process, commercially available microcrystalline cellulose was first modified by long-chain stearic acid to form hydrophobic microcrystalline cellulose ester and then mixed with stearic acid as filler in the subsequent surface coating of bagasse fibre paper. The microcrystalline cellulose ester/stearic acid-coated paper (MSP) exhibited good water repellency and oxygen barrier activity due to a continuous hydrophobic film that formed, which completely covered the pores of the original bagasse fibre paper. The coated MSP sample also showed excellent dimensional stability in water and a good wet tensile strength of 16 MPa. In addition, poly(hexamethylene guanidine) (PHMG) was chemically grafted onto the free carboxyl groups of the MSP surface layer, and the resulting MSP-g-PHMG samples exhibited excellent antibacterial activity against Escherichia coli and Listeria monocytogenes. The biodegradable cellulose-based MSP-g-PHMG sample significantly delayed the decay of raspberry during storage, indicating its potential application in food packaging.

Tunable Hydrophobic Octadienyl-Ether Nanocelluloses by In Situ Ultrasonication for Reinforced Polymers and Water-Resistant Paper

One-pot syntheses and in situ ultrasonication have been optimized to generate tunable and highly hydrophobic 2,7-octadienyl-ether (ODE) cellulose nanofibrils (CNFs). Using only butadiene sulfone to serve as dual reaction medium and precursor to 1,3-butadiene (1,3-BD) for telomerization with cellulose hydroxyls, the OH-to-ODE conversion significantly improved from ca. 0.7 to 1.2, 1.8, 3.1, and 4.1 mmol of ODE/g-cellulose at 103–110 °C for 1–2 h. Ultrasonication was highly effective and versatile in the direct disintegration of ODE-cellulose (ODE-cell) in nonpolar organic solvents and plant oils into ODE-CNFs as well as pretreating cellulose for improved functionalization. Mixing 2 wt % in situ ultrasonicated 1.2 mmol of ODE/g-cell improved the modulus of polybutadiene six times and the strength of poly(styrene-b-isoprene-b-styrene) three times, whereas in situ ultrasonication of 1.8 mmol/g-cell directly with linseed oil at merely 0.07 wt % created holistic biobased hydrophobic cellulose paper to resist water penetration while also significantly improving the tensile strength. This optimized telomerization and streamlined in situ ultrasonication approach has presented a sustainable synthesis and processing strategy to generate highly hydrocarbon-compatible nanocelluloses previously unattainable.

Preparation of high elastic bacterial cellulose aerogel through thermochemical vapor deposition catalyzed by solid acid for oil-water separation

Oil pollution has caused more and more serious damages to the environment, especially to water. Oil and water separation technologies based on high-performance absorbing materials have attracted extensive attentions. Herein, elasticity-enhanced bacterial cellulose (BC) aerogel is synthesized for oil/water separation through thermochemical vapor deposition (CVD) catalyzed by 1, 2, 3, 4-butanetetracarboxylic acid (BTCA). BTCA has two functions, namely, esterification with BC and catalyzing CVD. The prepared aerogel could be recovered soon after being compressed and the elastic recovery was >90 % at set maximum deformation of 80 %. And, it also exhibits vigorous fatigue resistance with an elastic deformation of >80 % after 50 cycles. The high elastic and hydrophobic aerogel is very suitable for absorbing and desorbing oils by simple mechanical squeezing. The adsorption capacity for n-hexane and dichloroethane maintain 87 % and 81 % after 50 cycles, respectively, which implies robust reusability. Importantly, the CVD could also be catalyzed by other solid acids such as citric acid and vitamin C. This design and fabrication method offers a novel avenue for the preparation of hydrophobic bacterial cellulose aerogel with high elasticity.

Hydrophobic carboxymethyl cellulose as a clean-up sorbent in the determination of nitrofuran metabolites in animal-fat samples

Hydrophobic-CMC biopolymers were fabricated for the removal of fat from food sample matrices. The CMCs were synthesized via the esterification of CMC with three alcohols with carbon chains of different lengths, in the presence of sulfuric acid.

Preparation of antifouling and highly hydrophobic cellulose nanofibers/alginate aerogels by bidirectional freeze-drying for water-oil separation in the ocean environment.

Oil spills frequently occur in the ocean, and adsorption is one of the effective ways to deal with oil spills. Compared with other adsorbent materials, biomass aerogel has superior selective adsorption capacity. CNF/SA aerogels with good mechanical properties (340kPa at 90 % strain) and high adsorption capacity (88.91g/g) were prepared by mixing cellulose nanofibers (CNF) with sodium alginate (SA) through bidirectional freeze-drying, ionic crosslinking, and surface modification to effectively solve the ocean oil spill problem. The bidirectional freeze-drying technology is a green and efficient technique for preparing layered microstructured composite aerogels. The prepared aerogels have a three-dimensional interpenetrating lamellar structure, low density (24.2mg/cm3), high porosity (97.85 %), and high hydrophobicity (WCA=144.5°), can be calibrated and used repeatedly. It has potential applications in water-oil separation and can be used as an absorbent for effectively treating oil spills in the ocean environment.

Aluminum Plasmonic Nanoclusters for Paper-Based Surface-Enhanced Raman Spectroscopy.

Although surface-enhanced Raman spectroscopy (SERS) can rapidly identify molecular fingerprints and has great potential for analysis, the need for delicate plasmonic substrates and complex laboratory instruments seriously limits its applicability for on-site detection. This paper describes the development of an inexpensive aluminum nanoparticle (AlNP)-decorated paper that functions as a facile SERS-based detection platform (Al-PSERS). Polydopamine-protected AlNPs were chemically synthesized and then simply drop-cast onto a hydrophobic cellulose paper, forming a monolayer AlNP cluster array. Because of the abundance of hot spots arising from the plasmonic clusters, the inherent quasi-three-dimensional structure of the cellulose fibers, and the concentration effect of the hydrophobic surface, the Al-PSERS provided significant enhancements to the signal of various analytes, measured using a portable 785 nm Raman spectrometer. Near-field optical simulations and experimental spectroscopic results revealed that the local electric fields and corresponding SERS signal intensities of the AlNP array exhibited clear particle-length and cluster-size dependencies. Therefore, the Al-PSERS could be optimized to provide high sensitivity (enhancement factor: 2 × 103) and excellent reproducibility (variation: 8.72%). Moreover, the optimal Al-PSERS was capable of detecting colorants and environmental pollutants; for example, the detection limits of allura red and benzo[a]pyrene reached as low as 3.5 and 0.15 ppm, respectively. Furthermore, the Al-PSERS could rapidly identify illegal (rhodamine B) and edible (allura red, erythrosine) colorants from a mixture of multiple colorants or from adulterated candies. Because it facilitates rapid detection, is of low cost, and has minimal technical requirements, Al-PSERS should be applicable to on-site detection in, for example, food inspection and environmental monitoring.

Preparing Hydrophobic Cellulose Nanofibers-SiO2 Films and Coating by One-Step Mechanochemical Method.

Green and sustainable cellulose-based hydrophobic coatings are increasingly the subject of scientific and industrial research. However, few researchers pay attention to preparing it by a one-step method. Therefore, a superhydrophobic coating composed of hydrophobic SiO2 and cellulose nanofiber modified by 3,4-dichlorophenyl isocyanate was manufactured through one-step ball milling. It was found that the ball milling can promote SiO2 dispersion and achieve the preparation of modified nanocellulose, which further disperse SiO2 nanoparticles to form film or coating. Compared with the ultrasonic dispersion method, the composite coating prepared by ball milling method can obtain higher water contact angle and more stable hydrophobic properties. The hydrophobic cellulose nanofiber can load 1.5 equivalents of SiO2 nanoparticles to form a uniform film with the water contact angle of 158.0° and low moisture absorption. When this nanocomposite is used as a coating material, it can impart super-hydrophobicity to paper surface with water contact angle of 155.8°. This work provides a facile way to prepare superhydrophobic nanocellulose/nanoparticles composite coatings and films, thereby broadening the ways of dispersing nanoparticles and constructing superhydrophobic coatings.

Hydrophobic Cellulose Acetate Aerogels for Thermal Insulation.

As naturally derived material, cellulose aerogels have excellent thermal insulation properties due to their unique high porosity and three-dimensional mesoporous structure. However, its hydrophilic properties limit its application in the field of building insulation. Here, we propose a method to prepare high hydrophobicity by adopting the sol-gel method and chemical vapor reaction strategy using cellulose acetate type II as raw material and 2,4-toluene diisocyanate as the cross-linking agent. Thermal properties of cellulose acetate aerogels (CAAs) were measured, where pyridine was the catalyst, acetone was the solvent, and perfluorodecyltriethoxysilane (PFDS), hexamethyldisilazane (HMDS), and methyltriethoxysilane (MTES) were used as hydrophobic agents (by process hydrophobic test). Compared with MTES-modified cellulose acetate aerogels (M-CAAs) and HMDS (H-CAAs)-modified cellulose acetate aerogels, PFDS-modified (P-CAAs) cellulose acetate aerogels are the most hydrophobic. By implementing hydrophobic modification of PFDS both inside and outside the structure of cellulose acetate aerogels, the water contact angle can reach up to 136°, strongly demonstrating the potential of PFDS as a hydrophobic agent. The results show that the thermal conductivity and compressive strength of cellulose acetate aerogel with the best hydrophobic properties are 0.035 W m−1 K−1 at normal pressure and 0.39 MPa at 3% strain, respectively. This work shows that the highly hydrophobic cellulose acetate aerogel has potential as a waterproof material in the field of building thermal-insulation materials.

Effect of Oil on Cellulose Dissolution in the Ionic Liquid 1-Butyl-3-methyl Imidazolium Acetate.

While ionic liquids (ILs) are well known to be excellent solvents for cellulose, the exact mechanism of dissolution has been a much disputed topic in recent years and is still not completely clear. In this work, we add to the current understanding and highlight the importance of hydrophobic interactions, through studying cellulose dissolution in mixtures of 1-butyl-3-methyl imidazolium acetate (BmimAc) and medium-chain triglyceride (MCT) oil. We demonstrate that the order in which constituents are mixed together plays a key role, through nuclear magnetic resonance (NMR) spectroscopic analysis. When small quantities of MCT oil (0.25–1 wt %) were introduced to BmimAc before cellulose, the effect on BmimAc chemical shift values was much more significant compared to when the cellulose was dissolved first, followed by oil addition. Rheological analysis also showed small differences in the viscosities of oil–cellulose–BmimAc solutions, depending on the order the constituents were added. On the other hand, no such order effect on the NMR results was observed when cellulose was replaced with cellobiose, suggesting that this observation is unique to the macromolecule. We propose that a cellulose–oil interaction develops but only when the cellulose structure has a sufficient degree of order and not when the cellulose is molecularly dispersed, since the hydrophobic cellulose plane is no longer intact. In all cases, cellulose–BmimAc–oil solutions were stable for at least 4 months. To our knowledge, this is the first work that investigates the effect of oil addition on the dissolving capacity of BmimAc and highlights the need for further re-evaluation of accepted mechanisms for cellulose dissolution in ILs.

Transparent Bioplastics from Super-Low Lignin Wood with Abundant Hydrophobic Cellulose Crystals

Bioplastics (BPs) prepared from lignocellulose are an excellent replacement for petrochemical-plastics (PCPs) due to their renewability and biodegradability. The presence of residual/added/regenerated lignin reduced the water sensitivity; however, these BPs possessed a deep color and low transmittance and were prone to photodegradation. Herein, we developed a UV- and water-insensitive, colorless, transparent, and sustainable wood-derived BP (W-BP) by pressing delignified wood (DW) with 0.21% lignin and abundant hydrophobic crystal plane (200) of cellulose. The DW was obtained by the pretreatment of the wood sample with NaOH/Na2SO3 followed by H2O2 steam conditioning. The abundant hydrophobic crystal plane (200) of cellulose in DW was demonstrated by a large ratio of the crystal plane (200) to (110), the presence of two-dimensional (2D) nanosheets of defibrated cellulose, and a low moisture uptake of 8.7% of the freeze-dried DW. The aged W-BP with a thickness of about 50 μm displayed good photostability with a ΔE* value of 2.3 and a transparency of 84% transmittance at 550 nm. Additionally, W-BP also possessed water stability with a wet tensile strength of 74 MPa and a low water uptake of 28.3%. These values exceeded those of lignocellulosic BPs and some commercial PCPs. The W-BP could replace transparent PCPs and provide indirectly experimental support to the lignin–cellulose interaction.

Acid- and Alkali-Resistant and High-Performance Cellulose Paper-Based Triboelectric Nanogenerator by Controlling the Surface Hydrophobicity

Cellulose paper-based triboelectric nanogenerators (CPTENGs) have gained considerable attention because they are low-cost, lightweight, flexible, and environmentally friendly. However, the poor triboelectric property and hydrophobicity of cellulose paper still limit the development of high-performance CPTENGs. In this work, octadecylamine (ODA) has been introduced onto cellulose fibers to prepare hydrophobic cellulose paper (HCP) by means of polydopamine (PDA) which can react with ODA and hydrogen bond with cellulose. Benefiting from the ODA and PDA co-modification, HCP exhibits excellent triboelectric property, surface roughness, and hydrophobicity; moreover, the HCP exhibits remarkable resistance to acids and alkalis. In addition, an HCP-based TENG (HCPTENG) shows an open-circuit voltage (VOC) of 237.8 V and a short-circuit current (ISC) of 4.2 μA, which are higher than those of the most of cellulose paper-based TENGs. More importantly, the HCPTENG shows great output performance stability when treated with water, acids, and alkalis. The HCPTENG with a retractable and collapsible lantern structure can harvest energy from human movement and detect the foot motion like walking and running and hand flapping.

The hydrophobicity and swelling of methyl cellulose coating synergistically enhancing the inkjet printing qualities of cotton fabric

Textile coated by natural polymer is an industrial method for enhancing the inkjet printing qualities. However, the hydrophobic modified polymer coating has been rarely reported. Here, the effect of hydrophobic methyl cellulose (MC) coating on the inkjet printing qualities of cotton fabric was investigated and compared with commonly used sodium alginate (SA) and sodium carboxymethyl cellulose (CMC) coatings. The results show that all three polymers could improve the sharpness and color depth of inkjet printing. However, the effect of the MC coating was far better than the SA and CMC coatings, which results from the different functional groups of the three polymers. Methyl groups make MC coating hydrophobic, while the SA and CMC coatings exhibit hydrophilicity. The hydrophobicity and swelling of the MC coating could synergistically reduce the spreading and penetrating of ink droplets. SA and CMC coatings rarely reduced the flow of ink droplets and only preserved part of ink by the swelling property. This work reveals the action mechanism of the polymer coating. And it is confirmed that the hydrophobic natural polymer coating is more effective than the hydrophilic coating to enhance the inkjet printing qualities.

Fabrication of Hydrophobic Cellulose Aerogels from Renewable Biomass Coir Fibers for Oil Spillage Clean-Up

Fabrication of Hydrophobic Cellulose Aerogels from Renewable Biomass Coir Fibers for Oil Spillage Clean-Up

Synthesis and characterization of nanofibrilated cellulose films modified with blocked isocyanates in aqueous media and their barrier properties to water vapor and oxygen

Hydrophobic nanofibrilated cellulose (NFC) films were prepared by the casting of a mixture of NFC suspension in an aqueous emulsion of two blocked isocyanates - one prepared by the reaction of 4,4′- methylenebis (phenyl isocyanate) and phenol (MDI-2Ph) and a commercial one from trimethylol propane and toluene diisocyanate (Desmodur AP Stabil®) (TMP-TDI-3Ph),). The drying procedure was performed in two steps, i.e., first at 60 °C for 24 h and then at 170 °C for 10 min. Infrared spectroscopy (FT-IR), elemental analysis, and 13 CNMR confirmed the chemical modification of cellulose. The NFC modified films showed an approximately 40 g m−2.day−1 water vapor transmission rate, which is almost 75% lower than that of non-modified NFC films (153 g m−2.day−1). The film modified with TMP-TDI-3Ph showed a very low oxygen transmission rate and lower than that with MDI-2Ph When exposed to a wet environment, the modified films maintained their stiffness with Young's modulus around 5 GPa, whereas that of non- modified films decreased from approximately 6.5 GPa to below 0.1 GPa.

Separation of Microplastic Particles from Sewage Sludge Extracts Using Magnetic Seeded Filtration

Microplastic particles (MP) are efficiently retained in wastewater treatment plants and enriched in sewage sludge. For monitoring MP contents in wastewater systems, sewage sludge is thus well suited, but also requires an isolation of MP from the sludge matrix, as other sewage sludge components may interfere with the MP identification and quantification. Although organic matter in sludge samples can be removed through acid and enzymatic digestion procedures, cellulose - mainly from toilet paper - remains in the digests, due to its high chemical resistivity and similar density to MP. We apply the separation concept of magnetic seeded filtration to isolate MP through selective hetero-agglomeration with magnetic seed particles. MP and cellulose differ in their hydrophobic properties and we investigate to what extent these differences can be exploited to selectively form MP-magnetite hetero-agglomerates in the presence of cellulose. These hetero-agglomerates are subsequently separated using a magnet. Five MP types (Polyethylene terephthalate (PET), polypropylene (PP), low density polyethylene (LDPE), polyvinyl chloride (PVC) and polystyrene (PS)) and cellulose particles were mixed in different combinations with both hydrophilic and hydrophobic (silanized) magnetite particles. PET, PP, LDPE and PS only poorly agglomerated with pristine (hydrophilic) magnetite, but efficiently formed hetero-agglomerates with hydrophobic magnetite and were successfully removed from suspensions (80−100%). PVC agglomerated more efficiently with pristine than with hydrophobic magnetite and cellulose only agglomerated to a limited extent with either hydrophilic or hydrophobic magnetite, resulting in a high process selectivity. Results from experiments conducted at different ionic strengths and with hydrophilic and hydrophobic magnetite suggests that the agglomeration process was dominated by hydrophobic interactions. Enzymatic and oxidative treatment of the MP only marginally affected the separation efficiencies and (treated) MP spiked to sewage sludge extracts were successfully recovered using magnetic seeded filtration.

Highly Transparent, Self-Reinforced, and Hydrophobic Cellulose Acetate Films Fabricated Based on Thermal Stretching and Surface Engineering

Imparting cellulose acetate with surface hydrophobicity and self-cleaning function without sacrificing its high transparency and mechanical robustness is a great challenge. In this work, we report a highly transparent, self-reinforced, and hydrophobic cellulose diacetate (CDA) film, prepared by the combination of non-solvent-induced phase separation, uniaxial thermal stretching, and slippery liquid injection (LI). Results indicate that the surface-modified CDA films have hydrophobicity, with the water contact angle (WCA) increasing from ∼58.2 to 105–109°. Meanwhile, by adjusting the draw ratio, the sliding of liquid on the film surface and the WCA hysteresis are effectively improved, especially the sliding angle of CDA-LI-1.7-200 film decreases from 30.5° (for the unmodified CDA film) to 9.4°. Notably, uniaxial stretching provides enhanced mechanical strength for this antifouling CDA film, with up to 60.2% increase in tensile strength (from 37.2 to 59.6 MPa). Meanwhile, it is noted that the modified CDA film also has excellent transparency (≥92%), even slightly higher than that of the unmodified CDA film (∼91.5%). In addition, the surface-modified CDA films show excellent anti-scratching performance and maintain good liquid repellency even after several cycles of severe scratching. The work would provide guidance for the facile preparation of high-performance and multifunctional CDA films.

Hydrophobic and lipophilic cellulose nanocrystal aerogel prepared by methyltrichlorosilane via vapor‐phase reaction

AbstractHydrophobic and lipophilic cellulose nanocrystal (CNC) aerogel was prepared by vapor‐phase reaction using methyltrichlorosilane (MTS). The water contact angle of the MTS‐CNC aerogel was up to 148.5°. The residual Cl element in MTS was negatable in the modified CNC aerogel. The MTS‐CNC aerogel only adsorbed the paraffin, but no water was adsorbed. The pseudo‐first‐order kinetic model could well describe the adsorption of the liquid paraffin oil on the CNC aerogel and the maximum adsorption capacity was about 60 g g−1 at 40°C. Multiple steps controlled the whole adsorption of oil on the MTS‐CNC aerogel, but 90% of the maximum adsorption capacity of paraffin was taken up in the first 1 min. The vacuum desorption could effectively remove the adsorbed oil at 80°C, and the good performance of the MTS‐CNC aerogel in adsorption and desorption was retained during 5 cycles. Therefore, the MTS‐CNC aerogel could be a potential candidate for removing oil from the oil‐spilled water system.

Vis-UV Upconverting bacteriostatic hydrophobic bacterial cellulose film for personal protective masks

Masks are key to personal protection and their bacteriostatic properties, which are generally overlooked, should be maximized. Towards this goal, a YPS-Pr-Li/BC upconversion antibacterial composite film was prepared by mixing upconversion powder with bacterial cellulose (BC) using a vacuum assisted method. When combined with the low surface energy of stearic acid (STA), the resulting YPS-Pr-Li/BC/STA film had an improved hydrophobic surface. The developed film was characterized by FT-IR, SEM, XRD, and fluorescence spectrophotometry. The results showed that the composite film was successfully prepared and had ultraviolet, visible upconversion luminescence. The bacteriostatic experiments showed that the material had excellent bacteriostatic performance against E. coli and S. aureus under visible light, with a bacteriostatic rate reaching 99 %. The in-vitro cytotoxicity tests showed that YPS-Pr-Li/BC/STA had excellent biocompatibility and could be used in personal protective clothing with close contact with human skin.

Preparation of micro-convex rough interface carbon aerogels with cellulose-lithium bromide (LiBr) molten salt hydrate gelled system and application of oil-water separation

As a novel nanoporous carbon material with high porosity, large specific surface area, excellent electrical conductivity and high temperature resistance, carbon aerogels have broad application prospects in the fields of catalyst carriers, energy storage and adsorption materials. In this work, the hydrophobic micro-convex rough interface cellulose carbon aerogels (CCAs) were fabricated via carbonization of cellulose-lithium bromide (LiBr) molten salt hydrate gelled system. The prepared CCAs shows a low density (0.016–0.023 g/cm3), high porosity (98.9–99.2 %), superior hydrophobicity (water contact angle over 135°) and excellent absorption of different oils and organic solvents. The absorption ability of CCAs 1.0-T800 for different oils and organic solvents can be 25–55 times its own weight. More importantly, the CCAs adsorbent can be reused by simple absorption/distillation method and still kept high-efficiency oil absorption capacity and excellent hydrophobicity after 5 absorption/elution cycles, displaying recyclability and robust stability. This study provides a green and facile way to fabrication of cellulose II carbon aerogels for application in spilled oil recovery, and exhibited highly promising as an economical, efficient and safe adsorbent for wastewater treatment.