Modified cellulose films with controlled permeatability and biodegradability by crosslinking with toluene diisocyanate under homogeneous conditions

Hydrophobic corn zein-modified cellulose nanofibril (CNF) films with antioxidant properties

Cellulose nanofibrils (CNFs) can form strong biodegradable films; however, due to their hydrophilicity, moisture can degrade their mechanical and barrier properties. Corn zein (CZ) is a hydrophobic protein that when covalently linked with CNF films through peptide bonds, may improve their hydrophobicity. CZ was covalently linked to aminophenylacetic acid and aminobenzoic acid esterified CNF films which were then assessed for evidence of modification, hydrophobicity, mechanical properties, and antioxidant activity. Upon modification, an increase in hydrophobicity and an increase in antioxidant activity as evidenced by 57% higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 26% higher (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) ABTS scavenging activities when compared to control CNF films, and reduced thio barbituric acid reactive substances (TBARS) values in canola oil during 14 days of 50 °C storage were noted. Results demonstrate that modification of CNF films with a hydrophobic protein such as CZ can increase the hydrophobicity of these biodegradable films while providing active antioxidant functionality.

Comparison of hydrophobic cellulose nanofibrils modified with different diisocyanates for circulating oil absorption

A large number of polluting substances, including chlorinated organic substances that were highly stable and hazardous, has been emitted due to the rapidly developing chemical industry, which will affect the ecological environment. Nanocellulose aerogels are effective carriers for adsorption of oil substances and organic solvents, however, the extremely strong hydrophilicity and poor mechanical properties limited their widespread applications. In this study, TEMPO-oxidized cellulose nanofibrils was modified with 2, 4-toluene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI) to prepare strong and hydrophobic aerogels for oil adsorption. The main purpose was to evaluate and compare the effects of two diisocyanates on various properties of modified aerogels. It was found that the modified aerogel had better hydrophobic properties, mechanical properties and adsorption properties. In particular, the modified aerogel with TDI as crosslinker showed a better performance, with a maximum chloroform adsorption capacity of 99.3 g/g, a maximum water contact angle of 131.3°, and a maximum compression stress of 36.3 kPa. This study provides further evidence of the potential of functional nanocellulose aerogel in addressing environmental pollution caused by industrial emissions.

Synthesis, characterization, and biodegradation studies of new cellulose-based polymers

New cellulose carbamates and cellulose acetate carbamates were prepared by classical addition reaction of isocyanates with alcohols. A Telomerization technique was used to make the grafted molecules strongly anchored and more hydrophobic. These molecules were grafted into cellulose and CA chains, respectively. The structures of the synthesized derivatives were confirmed using Nuclear Magnetic Resonance Spectroscopy, Fourier Transform Infrared and Thermogravimetric Analysis, and their solubility phenomenon was also established, and the carbamate derivatives showed better solubility compared to cellulose. Their ability to biodegrade was investigated, and it was concluded that Cell-P₁ and CA-P₁ derivatives are more biodegradable than the other samples. These results suggest that the resulting compounds can be used effectively in many useful industrial fields, for instance, eco-friendly food packaging, domains that use materials that are environmentally friendly and sustainable and the development of green chemistry.

Fully bio-based supramolecular gel based on cellulose nanowhisker gallate by cyclodextrin host-guest chemistry

Nowadays, supramolecular hydrogels have gained special importance and development of versatile approaches for their preparation as well as their new facile characterization strategies has elicited tremendous scientific interest. Herein, we demonstrate that modified cellulose nanowhisker with gallic acid pendant groups (CNW-GA) could effectively bind with CNW grafted with β-Cyclodextrin (CNW-g-β-CD) through HG interaction to form fully biocompatible and low-cost supramolecular hydrogel. Also, we reported an easy and efficient colorimetric characterization method for confirming HG complexation using naked eye. The possibility of this characterization strategy evaluated both experimentally and theoretically using DFT method. Also, phenolphthalein (PP) was used for visual detection of HG complexation. Interestingly, PP undergoes a rearrangement in its structure in presence of CNW-g-β-CD because of HG complexation that turns the purple molecule into a colorless compound in alkaline condition. Addition of CNW-GA to the resulting colorless solution turned the color to purple again which easily confirmed HG formation.

Effect of TDI-Assisted Hydrophobic Surface Modification of Microcrystalline Cellulose on the Tensile Fracture of MCC/PLA Composite, and Estimation of the Degree of Substitution by Linear Regression

Microcrystalline cellulose (MCC) was modified using toluene-2,4-diisocyanate (TDI) in tetrahydrofuran (THF). The reaction was set up for 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 24 h at 75 °C. The study was aimed at hydrophobic modification of microcrystalline cellulose (MCC) to improve its dispersion in PLA matrix. Data from the elemental analysis were used to develop a statistical model to predict the degree of substitution (DS) of the OH on the surface of the MCC using both the water contact angle (WCA) and the time of carbamation as the independent variables. Composite was fabricated at 1%, 2%, 3%, 4%, and 5% fiber loading. Fourier transformed infrared spectroscopy was used to characterize the MCC and to confirm the successful graft of TDI to the MCC surface. The morphology and elemental analysis of the modified samples were examined with SEM-EDX. The samples' wettability was analyzed with a contact angle meter to measure the water contact angle (WCA). The tensile properties of composites were analyzed on a universal testing machine. The result showed that, after 1 h of carbamation, the minimum DS recorded was 0.11, and the maximum DS after 24 h was 0.16. The SEM revealed that the modified MCC had homogeneous dispersion in the polymer matrix. At 3% fiber loading, the tensile strength (TS) and elongation were at a maximum and had improvements of 80.67% and 79.44% as compared to neat PLA. The fractured tensile surface from SEM analysis showed that surface modification enhanced fiber-matrix adhesion and significantly improved the composite's strength and toughness. The proposed model that was developed in this study had a coefficient of determination (R²) of 93% to show that the model has a near-perfect goodness of fit and can well be an effective approach to predict the DS of OH from WCA and the time of reaction at similar or the same reaction conditions.

Synthesis and characterization of eco-friendly cellulose beads for copper (II) removal from aqueous solutions

In this study, novel cellulose-bead-based biosorbents (CBBAS) were successfully synthesized from almond shell using a simple three-step process: (i) dissolution of bleached almond shell in ionic liquid (1-butyl-3-methylimidazolium chloride), (ii) coagulation of cellulose-ionic liquid solution in water and (iii) freeze-drying. Their morphological, structural and physicochemical properties were thoroughly characterized. These biomaterials exhibited a 3D-macroporous structure with interconnected pores, which provided a high number of adsorption sites. It should be noted that CBBAS biosorbents were efficiently employed for the removal of copper (II) ions from aqueous solutions, showing high adsorption capacity: 128.24 mg g^-1. The biosorption equilibrium data obtained were successfully fitted to the Sips model and the kinetics were suitably described by the pseudo-second-order model. Besides, CBBAS biosorbents can be easily separated from the solution for their subsequent reuse, and thus, they represent a method for the removal of copper (II) from aqueous solutions that is not only eco-friendly but also economical.

Cellulose based materials for controlled release formulations of agrochemicals: A review of modifications and applications

Controlled release formulations (CRFs) of agrochemicals have been attracted considerable attention due to their friendliness to environment. The commercial supporting materials for CRFs of agrochemicals are non-degradable, leading to secondary pollution issue. Cellulose, as the most abundant natural materials in the world, is regarded as one of the most ideal substitutes for non-degradable supporting materials thanks to its good biocompatibility and biodegradability. As raw cellulose materials suffer several problems, such as poor mechanical strength, fast release rate, etc., chemical modifications are commonly performed to improve their properties. In this review, modification methods of cellulose materials for CRFs of agrochemicals were introduced. The relationships between release rate and cellulose based materials were discussed in detail. The applications of cellulose materials for CRFs of agrochemicals were also expounded.

Effects of Biodegradation on the Structure and Properties of Windmill Palm (Trachycarpus fortunei) Fibers Using Different Chemical Treatments

In this work, windmill palm fiber (WPF), alkali-treated fiber (AF) without hemicellulose and bleached fiber (BF) without lignin were prepared and buried in soil for 30, 60 and 90 days. The surface morphology, chemical composition, crystallinity degree, mechanical properties, and residual mass rate of the samples, before and after biodegradation, were investigated. According to the results, soil burial degradation can remove the parenchyma cells and silica-bodies of WPF and deplete droplets containing the lignin of alkali-treated fiber after it has been buried for 30 days (AF30), and degradation of the single fiber cell wall of bleached fiber after it has been buried for 30 days (BF30). Buried in natural soil, lignin has a slower degradation rate than that of hemicellulose. WPF showed no significant differences in tensile strength after burial in soil for 90 days, because of the integrity fiber structure decreased the biodegradation. The most serious decrease, about 43%, in tensile strength occurred in AF after it had been buried for 90 days (BF90). This basic knowledge may be helpful for windmill palm fiber applications, especially for biodegradable composites.

Fluorescent Covalently Cross-Linked Cellulose Networks via Light-Induced Ligation

A facile light-induced procedure for the covalent cross-linking of cellulose at ambient conditions employing the nitrile imine mediated tetrazole-ene cycloaddition (NITEC) reaction is presented. Cellulose-tetrazoles with 2 degrees of substitution (0.14 and 0.23) were synthesized in a solution-based transesterification procedure in an ionic liquid. Two bismaleimides with either a trioxatridecane or a dithiodipropionyl backbone were used as cross-linkers to form fluorescent, covalently cross-linked cellulose networks and films, which were characterized by UV/vis spectroscopy, fluorescence spectroscopy, DSC, and TGA. The films showed a broad emission band from 500-700 nm and were thermally stable up to 200 °C. Using the bismaleimide with a disulfide moiety as the cross-linker, reductive degradation of the films can be induced. Finally, cellulose-tetrazole was cross-linked in a spatially resolved fashion, providing a strategy for the shaping of films based on renewable resources.

Cross-linked methyl cellulose/graphene oxide rate controlling membranes for in vitro and ex vivo permeation studies of diltiazem hydrochloride

Permeability characteristics of the anti-hypertensive drug, diltiazem hydrochloride, from uncross-linked and cross-linked methylcellulose (MC)/graphene oxide (GO) rate controlling membranes (RCMs) were investigated.

Tunable mesoporous bilayer photonic resins with chiral nematic structures and actuator properties

Chiral nematic structures with different helical pitch from layer to layer are embedded into phenol-formaldehyde bilayer resin composite films using cellulose nanocrystals (CNCs) as templates. Selective removal of CNCs results in mesoporous resins with different pore size and helical pitch between the layers. Consequently, these materials exhibit photonic properties by selectively reflecting lights of two different wavelengths and concomitant actuation properties.

Enhancement of the controlled-release properties of chitosan membranes by crosslinking with suberoyl chloride

A novel crosslinking agent, suberoyl chloride, was used to crosslink N-phthaloyl acylated chitosan and improves the properties of chitosan membranes. Membranes with different crosslinking degrees were synthesized. The derivatives were characterized by Fourier transform infrared spectroscopy and ¹³C solid state nuclear magnetic resonance spectroscopy, which indicated that the crosslinking degrees ranged from 0 to 7.4%. The permeabilities of various plant nutrients, including macroelements (N, P, K), microelements (Zn²⁺ and Cu²⁺), and a plant growth regulator (naphthylacetic acid), were varied by moderate changes in crosslinking degree, indicating that the controlled-release properties can be regulated in this way. The film-forming ability of native chitosan was maintained, whilst mechanical properties, hydrophobicity and controlled permeability were improved. These dramatic improvements occurred with a small amount of added suberoyl chloride; excessive crosslinking led to membranes with unwanted poor permeability. Thus, both the mechanical properties and permeability of the crosslinked membrane can be optimized.