Regenerated Cellulose Films Research Articles

A flexible paper transistor made with aligned single-walled carbon nanotube bonded cellulose composite

We report a flexible paper transistor made with single-walled carbon nanotubes covalently bonded cellulose (SCBC) composite without any additional semiconducting layer. Single-walled carbon nanotubes are covalently grafted to cellulose fibrils in a regenerated cellulose film to form the SCBC composite followed by a mechanical stretching process. The SCBC transistor shows a remarkable current–voltage characteristic depending on the stretching ratio. We found that the alignment of covalently bonded carbon nanotube plays a role that governs the electrical channel behavior of the SCBC composite.

Effects of Solvent Systems on Its Structure, Properties and Electromechanical Behavior of Cellulose Electro-Active Paper

This paper reports a comparative study on the influence of solvent systems on its structure, properties and electromechanical behavior of cellulose electro-active paper. Three types of solvent systems, namely N,N’-dimethylacetamide (DMAc)/LiCl, Trifluoroacetic acid (TFA) and 1-butyl-3-methylimidazolium chloride (BMICL) were studied to dissolve cellulose. Regenerated cellulose from DMAc/LiCl showed the best thermal and tensile properties whereas cellulose regenerated from BMICL exhibited high bending deformation with poor thermal and tensile properties, which might be due to the entrapped residual ionic liquid upon regeneration process. The cellulose regenerated with TFA showed the lowest thermal stability and tensile strength. Details of fabrication and characterization of regenerated cellulose films from three solvent systems are explained. Keywords: Cellulose, DMAc/LiCl, TFA, BMICL, Thermal stability, Mechanical properties, Electromechanical behavior, Cellulose Regeneration, Thermal and Tensile Properties, Electromechanical Behavior

Biodegradable transparent substrates for flexible organic-light-emitting diodes

Electronics on flexible and transparent substrates have received much interest due to their new functionalities and high-speed roll-to-roll manufacturing processes. The properties of substrates are crucial, including flexibility, surface roughness, optical transmittance, mechanical strength, maximum processing temperature, etc. Although plastic substrates have been used widely in flexible macroelectronics, there is still a need for next-generation sustainable, high-performance substrates which are thermally stable with tunable optical properties and a higher handling temperature. In this communication, we focus on cellulose-based transparent, biodegradable substrates incorporating either nanopaper or a regenerated cellulose film (RCF). We found that both their optical and mechanical properties are dramatically different due to the difference of their building blocks. Highly flexible organic-light-emitting diodes (OLEDs) are also demonstrated on the biodegradable substrates, paving the way for next-generation green and flexible electronics.

A bioplastic with high strength constructed from a cellulose hydrogel by changing the aggregated structure

The direct use of cellulose to fabricate materials such as common plastics as synthetic polymers has hardly been investigated. In the present paper, bioplastics of a new class are constructed, for the first time, by hot-pressing cellulose hydrogel, and are different from common plastics in terms of their processability. The cellulose hydrogels were prepared from cellulose solution in an alkali hydroxide/urea aqueous system with cooling by physical cross-linking. Due to the removal of cellulose molecules in the hydrogel state, the hot-pressing induced a transition in the aggregated structure in the cellulose bioplastics, leading to a plastic deformation. The results from 13C NMR, SEM, and FT-IR confirmed that a radial orientation of cellulose molecules occurred in the planar direction of the plate, whereas an increase of amorphous zones appeared in the vertical direction. The resulting cellulose bioplastics were transparent, as a result of the uniformly orientated structure. Moreover, the cellulose bioplastic exhibited much higher tensile strength, flexural strength and thermal stability as well as a lower coefficient of thermal expansion than common plastics and regenerated cellulose films. The whole life cycle assessment showed that the cellulose bioplastic is an environmentally friendly material. This work opens up a completely new avenue to construct a valuable bioplastic directly from cellulose pulps rather than their derivatives.

A Facile Approach to Prepare Regenerated Cellulose/Graphene Nanoplatelets Nanocomposite Using Room-Temperature Ionic Liquid

This study presents the preparation of regenerated cellulose (RC)/graphene nanoplatelets (GNPs) nanocomposites via room temperature ionic liquid, 1-ethyl-3-methylimidazolium acetate (EMIMAc) using solution casting method. The thermal stability, gas permeability, water absorption and mechanical properties of the films were studied. The synthesized nanocomposite films were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The T20 decomposition temperature of regenerated cellulose improved with the addition of graphene nanoplatelets up to 5 wt%. The tensile strength and Young's modulus of RC films improved by 34 and 56%, respectively with the addition of 3 wt% GNPs. The nanocomposite films exhibited improved oxygen and carbon dioxide gas barrier properties and water absorption resistance compared to RC. XRD and SEM results showed good interaction between RC and GNPs and well dispersion of graphene nanoplatelets in regenerated cellulose. The FTIR spectra showed that the addition of GNPs in RC did not result in any noticeable change in its chemical structure.

Preparation of copper nanoparticles coated cellulose films with antibacterial properties through one-step reduction

Regenerated cellulose (RC) films coated with copper (Cu) nanoparticles were prepared from cellulose-cuprammonium solution through coagulation in aq. NaOH and subsequent reduction in aq. NaBH4. Structure and morphology of the nanocomposite films were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The results established the migration of Cu(2+) from the inner to the surface of the RC films during the coagulation of cellulose-cuprammonium solution and the reduction from Cu(2+) to Cu(0). Cu nanoparticles were found to be firmly embedded on the surface of the RC films. The RC films coated with Cu nanoparticles showed efficient antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The dramatic reduction of viable bacteria could be observed within 0.5 h of exposure, and all of the bacteria were killed within 1 h.

Preparation and characterization of regenerated cellulose blend films containing high amount of poly(vinyl alcohol) (PVA) in ionic liquid

Regenerated cellulose/poly(vinyl alcohol) (PVA) blend films in ionic liquid 1-allyl-3-methylimidazolium chloride (AMIMCl) were successfully prepared by coagulating with water. The structures and properties were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). SEM images indicated that there was good compatibility between cellulose and PVA. The XRD results showed that the crystallinity of cellulose was significantly decreased from 42.8% up to 29.4% with increasing PVA content. The blend film with a 10 wt% PVA demonstrated the best mechanical performance. Its tensile strength and modulus showed 97 and 5,100 MPa, respectively compared with 69 and 3,400 MPa of neat cellulose film. The elongation also increased 50%. In addition, the transparency of the blend lms was still maintained well, and the shrinkage of the regenerated cellulose film was greatly improved with incorporation of PVA. The possible mechanism of forming cellulose/PVA blend films was proposed in the process of regeneration and dissolution.

Improvement of mechanical and oxygen barrier properties of cellulose films by controlling drying conditions of regenerated cellulose hydrogels

Mechanical, thermal and oxygen barrier properties of regenerated cellulose films prepared from aqueous cellulose/alkali/urea solutions can be markedly improved by controlling the drying conditions of the films. By pre-pressing followed by vacuum drying under compression, the tensile strength, Young’s modulus, coefficient of thermal expansion and oxygen permeability of the dried films reached 263 MPa, 7.3 GPa, 10.3 ppm K−1 and 0.0007 ml μm m−2 day−1 kPa−1, respectively. Thus, films produced in this way show the highest performance of regenerated cellulose films with no orientation of cellulose chains reported to date. These improved properties are accompanied by a clear increase in cellulose II crystallinity from 50 to 62% during pre-pressing/press-vacuum drying process. At the same time, the film density increased from 1.45 to 1.57 g cm−3, and the moisture content under equilibrium conditions decreased from 14.1 to 9.8%. Hence, the aqueous alkali/urea solvent system has potential applications in producing new and environmentally friendly cellulose films with high performances through control of the drying conditions.

Influence of residual ionic liquid on the thermal stability and electromechanical behavior of cellulose regenerated from 1-ethyl-3-methylimidazolium acetate

The regenerated cellulose films were prepared by dissolving cotton cellulose pulp directly in room temperature ionic liquid namely, 1-ethyl-3-methylimidazolium acetate at 80 °C, followed by washing/curing in different coagulants namely, methanol, deionized water, methanol-deionized water, and isopropyl alcohol-deionized water. It was found that the type of coagulants employed for curing the cellulose films has a significant influence on the amount of residual ionic liquid entrapped in the films. The amount of residual ionic liquids was 2.68, 1.01, 0.84, and 0.75 wt.% for the films cured with deionized water, isopropyl alcohol-deionized water, methanol, and methanol-deionized water, respectively. The DTG peaks of regenerated cellulose films showed two decomposition temperatures at 280 °C and 320 °C. Among all the cases studied, deionized water curing case showed the lowest decomposition temperature, attributed to entrapment of large residual ionic liquid in it. Electromechanical characteristic of the regenerated cellulose films was also investigated.

Preparation and characterization of regenerated cellulose/poly (vinylidene fluoride) (PVDF) blend films

Regenerated cellulose/poly (vinylidene fluoride) (PVDF) blend film was successfully prepared through coagulating their N,N-dimethyl acetamide (DMAC)/LiCl solution with water. The toughness of the blend films, compared with virgin regenerated cellulose film, was significantly improved when the content of PVDF in blend films was no more than 20wt.%. The elongation at break increased from 12% to 34%, and the tensile strength was also improved from 89 to 106MPa with the addition of PVDF till 20wt.%. The mechanical properties of the blend films became worse when the content of PVDF in blend films was more than 20%. The oxygen permeability was firstly decreased from 2.3×10−10 to 0.036×10−10cm3cm/cm2sPa when the PVDF content increased from 0 to 5wt.% in the blend films. Afterwards, the oxygen permeability would increase with the increasing of the PVDF content. The film showed some pores when the loading level of PVDF was more than 50%. The pore size of blend film became larger with the increasing of PVDF content. These phenomena were well correlated to the crystallinity, hydrogen bonds and morphologies of the blend films.

Enzymatic digestion of partially and fully regenerated cellulose model films from trimethylsilyl cellulose

Partially and fully regenerated cellulose model films from trimethylsilyl cellulose (TMSC) were prepared by a time dependent regeneration approach. These thin films were characterized with contact angle measurements and attenuated total reflectance infrared spectroscopy (ATR-IR). In order to get further insights into the completeness of the regeneration we studied the interaction of cellulase enzymes from Trichoderma viride with the cellulose films using a quartz crystal microbalance with dissipation (QCM-D). To support the results from the QCM-D experiments capillary zone electrophoresis (CZE) and atomic force microscopy (AFM) were applied. The changes in mass and energy dissipation due to the interaction of the enzymes with the substrates were correlated with the surface wettability and elemental composition of the regenerated films. The highest interaction activity between the films and the enzyme, as well as the highest cellulose degradation, was observed on fully regenerated cellulose films, but some degradation also occurred on pure TMSC films. The enzymatic degradation rate correlated well with the rate of regeneration. It was demonstrated that CZE can be used to support QCM-D data via the detection of enzyme hydrolysis products in the eluates of the QCM-D cells. Glucose release peaked at the same time as the maximum mass loss was detected via QCM-D. It was shown that a combination of QCM-D and CZE together with enzymatic digestion is a reliable method to determine the conversion rate of TMSC to cellulose. In addition QCM-D and AFM revealed that cellulase is irreversibly bound to hydrophobic TMSC surfaces, while pure cellulose is digested almost completely in the course of hydrolysis.

Structure and Properties of Regenerated Cellulose Film with Fluorocarbon Coating

Abstract Fluorocarbon coatings were deposited on the surface of regenerated cellulose films by RF magnetron sputtering, using polytetrafluoroethylene targets. Argon was used as the working gas. The coatings were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, static contact angle and oxygen permeability measurements. It was found that the coatings were made up of the four components -CF3, -CF2-, -CF- and -C-. The [F]/[C] ratio varied with sputtering conditions. The surface of fluorocarbon coatings had an undulate island structure. The static contact angle of the coatings was greater than 90° at lower power and higher pressure, and the substrate material was transformed from hydrophilic to hydrophobic character. The fluorocarbon coatings were porous and did not influence the oxygen permeability of the cellulose film substrates.

Effects of plasticization conditions on the structures and properties of cellulose packaging films from ionic liquid [BMIM]Cl

AbstractBy using natural softwood pulp with higher degree of polymerization (DP = 1460) as cellulose source, 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) ionic liquid as solvent and glycerol as plasticizer, a novel cellulose packaging film was prepared. The effects of plasticization conditions on the structures, mechanical properties, permeability for oxygen and water vapor were measured by Wide‐angle X‐ray scattering, thermogravimetric analysis, scanning electron microscopy (SEM), and other techniques. The investigations suggested that the glycerol concentration and plasticizing time had great effect on the properties of the regenerated cellulose films. The crystal transformation of cellulose I to cellulose II occurred during the dissolution and regeneration process, combining with the decrease of thermal stability. The tensile strength decreased rapidly with the addition of glycerol and prolongation of plasticizing time. However, elongation at break of the regenerated cellulose films increased at first and then decreased with increasing of glycerol concentration and plasticizing time. The morphologies for the fracture surface obtained from SEM images showed transformation of typical brittle fracture to plastic deformation with increasing of glycerol concentrations. It was also found that both water vapor permeability and oxygen permeability of the regenerated cellulose films decreased slowly with increasing of glycerol concentrations and plasticizing time, but water vapor permeability and oxygen permeability presented an almost opposite trend. The films prepared by using ionic liquid technology would be used in food packaging or other fields as a kind of green packaging material. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Regenerated cellulose/graphene nanocomposite films prepared in DMAC/LiCl solution

Abstract Regenerated cellulose/graphene composite films had been prepared by dispersing graphene into cellulose solution in DMAC/LiCl, and then casting the solution onto glass. The thermal stability and mechanical properties of the composite materials, compared with pure regenerated cellulose film, were significantly improved. When the graphene loading was only 0.4 wt.%, the 10% weight loss temperature increased 20 °C. The Young's modulus increased from 3.4 to 7.2 GPa, while tensile strength increased from 89 to 148 MPa when 1.6 wt.% graphene was added into cellulose film. The electrical conductivity of the nanocomposite film reached 3.7 × 10−6 S/cm when 1.6 wt.% graphene was incorporated. The morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The images revealed that the graphene was nano-dispersed in cellulose matrix. The effect of the graphene content in the nanocomposite material was also investigated.

The study of regenerated cellulose films toughened with thermoplastic polyurethane elastomers

Regenerated cellulose blend film with thermoplastic polyurethane (TPU) was successfully prepared by coagulating cellulose/TPU solution with water in the presence of a thermoplastic polyurethane elastomer (TPU). Compared with pristine regenerated cellulose film, the toughness and thermal stability of the blend film was significantly improved. For example, the elongation at break was increased from 11% of pristine cellulose film to 51% of blend film with 20 wt. % TPU. The 50% weight loss temperature of this blend film was increased by 33 °C compared to neat cellulose. The relaxation transition temperature of cellulose was decreased with the addition of TPU through dynamic mechanical thermal analysis. The oxygen permeability was decreased from 2.3 × 10−10 cm3 cm/cm2 s Pa of pristine cellulose film to 0.08 × 10−10 cm3 cm/cm2 s Pa of the blend film with 20 wt.%. TPU The X-ray diffraction spectra showed that the crystallinity of cellulose decreased with incorporation of TPU. The images of scanning electron microscope discovered that there was good compatibility between cellulose and TPU. TPU was nano-dispersed in cellulose matrix. The blend film still maintained quite good transparency.

Cellulose scaffold: A green template for the controlling synthesis of magnetic inorganic nanoparticles

Utilization of environmentally benign solvents, nontoxic chemicals, and renewable materials are some of the key issues that merit important consideration in a green synthetic strategy. In this work, monodispersed magnetic Fe2O3 nanoparticles have been synthesized by using regenerated cellulose films as sacrificial templates. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) images indicated that the particle size of the nanoparticles was less than 50 nm. The nanoparticles had novel magnetic responsibility at room temperature and could be dispersed in water and kept at stable state for about 3 months. The nanoparticles were prepared directly without a size-selection process, and the synthetic procedure was reproducible. Furthermore, this method was facile and the process was completely green, which made this process amenable to the further development of green nanoparticle synthesis on a large-scale.

Hybrid nanocomposite based on cellulose and tin oxide: growth, structure, tensile and electrical characteristics

A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO2) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO2 was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current–voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose–SnO2 hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.

Structure and Properties of Regenerated Cellulose Film with Fluorocarbon Coating

Fluorocarbon coatings were deposited on the surface of regenerated cellulose films by RF magnetron sputtering, using polytetrafluoroethylene targets. Argon was used as the working gas. The coatings were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and static contact angle and oxygen permeability measurements. It was found that the coatings were made up of the four components -CF3, -CF2-, -CF- and -C-. The [F]/[C] ratio varied with sputtering conditions. The static contact angle of the coatings was greater than 90° at lower power and higher pressure, and the substrate material was transformed from hydrophilic to hydrophobic character. The fluorocarbon coatings were porous and did not influence the oxygen permeability of the cellulose film substrates.

Novel regenerated cellulose films prepared by coagulating with water: Structure and properties

Regenerated films were successfully prepared from cellulose/NaOH/urea solution by coagulating with water at temperature from 25 to 45°C. The results of solid 13C NMR, wide angle X-ray diffraction, scanning electron microscopy (SEM) and tensile testing revealed that the cellulose films possessed homogeneous structure and cellulose II crystalline, similar to that prepared previously by coagulating with 5wt% H2SO4. By changing the coagulation temperature from 25 to 45°C, tensile strength of the films was in the range of 85–139MPa. Interestingly, the RC35 film coagulated at 35°C exhibited the highest tensile strength (σb=139MPa). The inclusion complex associated with cellulose, NaOH and urea hydrates in the cellulose solution were broken by adding water (non-solvent), leading to the self-association of cellulose to regenerate through rearrangement of the hydrogen bonds. This work provided low-cost and “green” pathway to prepare cellulose films, which is important in industry.

Equilibrium Water Contents of Cellulose Films Determined via Solvent Exchange and Quartz Crystal Microbalance with Dissipation Monitoring

Model cellulose surfaces have attracted increasing attention for studying interactions with cell wall matrix polymers and as substrates for enzymatic degradation studies. Quartz crystal microbalance with dissipation monitoring (QCM-D) solvent exchange studies showed that the water content of regenerated cellulose (RC) films was proportional to the film thickness (d) and was consistent with about five water molecules per anhydroglucose unit. Sulfated nanocrystalline cellulose (SNC) and desulfated nanocrystalline cellulose (DNC) films had comparable water contents and contained about five times more water than RC films. A cellulase mixture served as a probe for studies of substrate accessibility and degradation. Cellulase adsorption onto RC films was independent of d, whereas degradation times increased with d. However, adsorption onto SNC and DNC films increased with d, whereas cellulase degradation times for DNC films were independent of studied d. Enhanced access to guest molecules for SNC and DNC films revealed they are more porous than RC films.