A major stumbling block in large-scale adoption of high-energy-density electrochemical devices has been safety issues. Methods to control thermal runaway are limited by providing a one-time thermal ...protection. Herein, we developed a simple and reversible thermoresponsive electrolyte system that is efficient to shutdown the current flow according to temperature changes. The thermal management is ascribed to the thermally activated sol–gel transition of methyl cellulose solution, associated with the concentration of ions that can move between isolated chains freely or be restricted by entangled molecular chains. We studied the effect of cellulose concentration, substituent types, and operating temperature on the electrochemical performance, demonstrating an obvious capacity loss up to 90% approximately of its initial value. Moreover, this is a cost-effective approach that has the potential for use in practical electrochemical storage devices.
In this study, calcium borate (CB) nanoparticles were in-situ grown onto cellulose acetate-laurate (CAL) template to prepare CB/CAL nanocomposite with uniform dispersion of CB nanoparticles by ...hydrothermal method. As-prepared CB/CAL nanoparticles were characterized by field emission scanning electron microscope, Fourier transforms infrared spectrometry, X-ray diffraction, and energy-dispersive X-ray spectroscopy. With average wear scar diameter (WSD), coefficient of friction (COF) and maximum non-seizure load (PB) as evaluation criterions, CB/CAL, CAL, and CB were used as lubricant additives in poly-alpha-olefin (PAO) base oil to comparatively investigate the tribological properties with a four-ball tribotester. It was found that under the load of 490 N, the WSD and COF of PAO + CB/CAL (concentration of 0.6 wt%) reduced by 25.9% and 48.7%, respectively, and PB increased by 79.6% compared with pure PAO base oil. CB/CAL nanocomposite exhibited superior lubricating performances than CB and CAL. In addition, the synergistic lubricating mechanism of CB/CAL nanocomposite as lubricant additive was explored.
•In-situ synthesis of calcium borate/cellulose acetate-laurate (CB/CAL) nanocomposite.•CB nanoparticles uniformly grew on the surface of CAL to avoid agglomeration.•CB and CAL exhibited synergistic anti-friction effect during the process of friction.•CB/CAL nanocomposite had excellent extreme pressure and anti-wear properties.•CB/CAL nanocomposite was used as an environmental friendly lubricant additive.
•New cellulose esters were synthesized by condensation of cellulose and aleuritic acid.•The mechanical behavior was changed from rigid to ductile, keeping the same toughness.•These materials show ...similar properties to commercial cellulose derivatives.
The synthesis of microcrystalline cellulose (MCC) and 9,10,16-hydroxyhexadecanoic (aleuritic) acid ester-based bioplastics was investigated through acylation in a mixed anhydride (trifluoroacetic acid (TFA)/trifluoroacetic acid anhydride (TFAA)), chloroform co-solvent system. The effects of chemical interactions and the molar ratio of aleuritic acid to the anhydroglucose unit (AGU) of cellulose were investigated. The degree of substitution (DS) of new polymers were characterized by two-dimensional solution-state NMR and ranged from 0.51 to 2.60. The chemical analysis by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) confirmed the presence of aleuritate groups in the structure induces the formation of new H-bond networks. The tensile analysis and the contact angle measurement confirmed the ductile behavior and the hydrophobicity of the prepared bioplastics. By increasing the aleuritate amounts, the glass transition temperature decreased and the solubility of bioplastic films in most common solvents was improved. Furthermore, this new polymer exhibits similar properties compared to commercial cellulose derivatives.
Long/short chain mixed cellulose esters (MCE) are practical, promising polymers with interesting properties. In the molecular design of MCE, using long acyl chains made from renewable resources is ...important and enhances the value of MCE as sustainable materials. In this study, we focused on two types of renewable long acyl chains for MCE: the aromatic 3-pentadecylphenoxy acetyl (PA) group derived from cardanol extracted from cashew nutshells and the aliphatic stearoyl (St) group made from vegetable oils. Using these long acyl chains and the acetyl (Ac) group as a short acyl chain, we synthesized PA/Ac MCE (P-series) and St/Ac MCE (S-series) in LiCl/DMAc medium. The thermal and mechanical analyses revealed that a mixed substitution of long and short acyl chains prevented the crystallization of the long acyl chain moieties in MCE. The P-series had slightly higher bending strength and glass transition temperature than those of the S-series but showed low impact strength because of the existence of the aromatic ring in the PA group, which caused an increase in the stiffness of the cellulose backbone and the extra intermolecular interaction. However, the S-series without aromatic rings showed remarkably improved impact strength with sufficient balanced mechanical properties for use in durable products due to its composition of low crystalline long acyl chain moieties.
•The molar mass of cellulose was decreased in a controlled manner.•Cellulose molar mass has a clear effect to the cellulose palmitates DS and properties.•Cellulose palmitates with decreased molar ...mass form transparent heat-sealable films.•Molar mass controlled palmitate films have excellent water barrier properties.
Nowadays one of the growing trends is to replace oil-based products with cellulose-based materials. Currently most cellulose esters require a huge excess of chemicals and have therefore, not been broadly used in the industry. Here, we show that decreasing the molar mass of cellulose by ozone hydrolysis provides cellulose functionalization with less chemical consumption. To reveal the differences in reactivity and chemical consumption, we showed esterification of both native cellulose and ozone treated hydrolyzed cellulose. Based on the results, the molar mass of the starting cellulose has a significant effect on the end product’s degree of substitution and properties. Furthermore, molar mass controlled palmitate esters form mechanically strong, flexible and optically transparent films with excellent water barrier properties. We anticipate that molar mass controlled cellulose will provide a starting point for the greater use of cellulose based materials, in various application, such as films and composites.
•Synthesis of cationic, water-soluble polymers from commercial cellulose esters.•Completely regio- and chemoselective modification.•Synthesis of C-6 azide, gateway to full range of amides, ...amines.•Amphiphilic polyelectrolytes for biomedical applications.
Cellulose-based materials are well-suited for biomedical uses, because of their abundance, renewable nature, biodegradability, and relatively low cost. However, the set of commercially available cellulose esters and ethers is limited in number and diversity, and contains no cationically charged cellulose esters. Herein we report a simple, efficient strategy for synthesizing cationic, water-soluble co-polyelectrolytes from commercial, hydrophobic, renewable-based cellulose esters. Cellulose acetate (degree of substitution (DS) 1.78, CA320S), was the exemplary starting material for preparing these cationic polyelectrolytes by a reaction sequence of phosphine-catalyzed bromination and subsequent displacement by an aromatic amine, affording high reaction conversions. We show that these modification techniques can be carried out with essentially complete regio- and chemoselectivity, proceeding in the presence of multiple ester groups, yet preserving those groups. Availability of these novel polysaccharide-based electrolytes starting from uncharged, commercial, inexpensive cellulose esters may open up multiple new application areas, including in several aspects of gene or drug delivery.
Fatty acid cellulose esters with excellent water repellency and improved processability have gained a lot of attention in varied applications. In this study, a “green” synthetic route employing ...mechanochemical reaction methods was developed to prepare long-chain cellulose esters from cellulose fibers. Specifically, cellulose fibers were ball-milled to prepare activated cellulose particles; asymmetric mixed anhydrides from acetic anhydride and oleic acid were formed for improved esterification reactivity. Cellulose powder and mixed anhydride were mechanochemically reacted during ball-milling. The effects of the catalyst, ball-milling time, and reagent molar ratio were investigated. The results revealed that ball-milling was shown to be an effective approach to modifying the surface of cellulose powder with acetic–oleic mixed chains. The adding of a catalyst accelerated the reaction greatly. Increasing the ball-milling time and raising the mixed anhydride molar fractions promoted the esterification of cellulose and increased the degree of substitution. The modified cellulose esters exhibited higher thermal stability and better water repellency than the untreated cellulose powders.
Recently, a wide range of large size draw solutes have been developed and employed in forward osmosis (FO) processes with the advantages of high water flux, minimum reverse flux and easy recovery. ...However, the high viscosity of these draw solutes tends to suffer from severer internal concentration polarization (ICP) and internal fouling within the sublayers. To solve these problems, a dual selective flat sheet membrane has been designed in this study in order to prevent the viscous draw solutes from entering the porous support layer and minimize the ICP effects. It consists of three layers: a top thin polyamide layer synthesized from interfacial polymerization, a middle porous cellulose ester layer, and another bottom thin polyamide layer. The dual selective thin film composite (TFC) membrane has a reasonably high water flux of 34.5LMH and a low salt reverse flux of 3.5gMH using DI water and 1M NaCl as the feed and draw solutions respectively under the FO mode. Comparing to single selective TFC membranes, the dual selective membrane significantly mitigated ICP effects and reduced fouling propensity using viscous draw solutes such as sucrose, ferric citric acid complex (Fe–CA) and polyethylene glycol monolaurate (PEG 640ML) as draw solutes. The newly developed dual selective membrane has great potential to maximize the effectiveness of viscous draw solutes in various FO processes.
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•A dual selective flat sheet membrane was designed for viscous draw solutes.•Viscous draw solutes such as sucrose, Fe–CA and PEG 640ML were studied.•The dual selective membrane exhibits high water fluxes with low salt reverse fluxes.•The dual selective membrane mitigates ICP effects and reduces fouling propensity.
Forward osmosis (FO) has developed as a new process with many potential applications in water production. The lack of an adequately designed membrane is the major challenge which hinders FO ...development. In this study, membrane science along with nanotechnology has been applied to build a high performance FO membrane. Boehmite nanoparticles, a hydrophilic additive containing extra hydroxyl groups on its surface, promoted cellulose acetate/cellulose triacetate (CA/CTA)-based membrane performance for FO applications. The characterization of the resultant nanocomposite membranes exhibited that the physiochemical properties, structural parameter and performance were improved. Loading 0.5wt.% of the nanoparticles enhanced the water permeability about three times without a considerable increase in salt permeability and produced an excellent permselectivity compared with the neat membrane. Moreover, the nanoparticle loading improved porosity of the nanocomposite membrane and reduced its structural parameter (S) to 0.53mm. Higher porosity and desirable hydrophilicity of the modified membrane exhibited a reduced impact of internal concentration polarization (ICP), which generally influenced the FO processes. The performance results indicated that the modified membrane showed a superior FO performance compared with the commercially available FO membranes.
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•Introducing hydrophilic boehmite nanoparticles into the CTA/CA polymer matrix•Boehmite improves both overall and surface porosity of the developed membrane•Improving structural parameter from 1.36 to 0.53mm as a result of boehmite loading•Enhancing FO water flux of the developed membrane without dropping its selectivity
Long chain cellulose esters are internally plasticized bio-based materials, which have good future potential in several applications such as coatings, films and plastics. The long chain cellulose ...esters with different side chain lengths were synthesized using different esterification methods. When homogeneous esterification was used, the acyl chloride method was the most effective esterification method and cellulose esters prepared using this method have the highest degree of substitution values (DS). In this case, the long chain cellulose esters showed DS values from 0.3 to 1.3 depending on the side chain length of cellulose esters. CDI activation, vinyl transesterification and anhydride routes resulted in somewhat lower DS values. The cellulose was also pretreated with ozone, which decreased cellulose molar mass, and resulted in synthesized cellulose esters having higher DS and better reaction efficiency than untreated cellulose. When heterogeneous esterifications were used, only acyl chloride method seemed to work.
Materials chemistry; Cellulose; Esterification; Long chain cellulose ester
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