Cellulose nanocrystals (CNCs) were incorporated into poly (vinylidene fluoride) (PVDF) to tailor the mechanical and dielectric properties of this electroactive polymer. PVDF/CNC nanocomposites with concentrations up to 15 wt.% were prepared by solvent-casting followed by quick vacuum drying in order to ensure the formation of the electroactive γ-phase. The changes induced by the presence of CNCs on the morphology of PVDF and its crystalline structure, thermal properties, mechanical performance and dielectric behavior are explored. The results suggest a relevant role of the CNC surface −OH groups, which interact with PVDF fluorine atoms. The real dielectric constant ε’ of nanocomposites at 200 Hz was found to increase by 3.6 times up to 47 for the 15 wt.% CNC nanocomposite due to an enhanced ionic conductivity provided by CNCs. The approach reported here in order to boost the formation of the γ-phase of PVDF upon the incorporation of CNCs serves to further develop cellulose-based multifunctional materials

A magnetic cellulosic material composed of cellulose nanocrystals (CNC) and cobalt ferrite (CoFe2O4) nanoparticles was developed through evaporation-induced self-assembly (EISA). Nanoparticles demonstrated good dispersibility within the cellulose nanocrystal template. The addition of glucose to CNC network allows the development of homogeneous crack-free CNC-based films and does no modify neither the morphology nor the optical properties. In contrast, the introduction of CoFe2O4 nanoparticles produces a marked decrease in the amount of the transmitted light. 20 wt.% of CoFe2O4 nanoparticles inside the CNC matrix induced a maximum magnetization value of 12.96 emu g−1, increased the real part of the dielectric constant (permittivity) from 10 (pure CNC film) to 12 and improved the thermostability of the nanocomposite as evidenced by the increase of the onset temperature from 165.1 to 220.4 °C. Those features obtained in a non-petroleum-based composite provide insight into the development of the next generation of functional materials from natural origin.

Polymers have been successfully used as electrode compounds and separator / electrolyte materials for lithium ion batteries (LiBs) due to their inherent outstanding properties such as low-density, easy of processing, excellent thermal, mechanical and electrical properties and easily tailored functional performance matching the final device requirements. Battery performance strongly depends on the polymer type used. The physico-chemical properties of the polymers that are being used as different battery components need to be further improved to boost the development of the next generation of batteries for the electric vehicle industry, where increased energy density and safety are required. Considering its role in LIBs, this review summarizes the latest advances in the field of polymers applied as electrode compounds and separator/electrolytes. For each battery component, the state-of-art is divided by polymer type. Current bottlenecks and challenges that face polymers in LIBs are shown, and possible strategies to face them are provided.

This work shows the effect of cellulose nanocrystal surface charge on the morphology, structure, thermal and dielectric properties of poly(vinylidene fluoride) nanocomposites. CNCs extracted through sulfuric acid hydrolysis were modified using sodium hydroxide and cationization treatments to yield CNCs with zeta-potential values of − 26.1 ± 3.7 and − 4.4 ± 0.3 mV in comparison with the original highly-negative − 45.2 ± 1.1 mV. Nanocomposites where then obtained through doctor-blade casting followed by room temperature drying. CNC incorporation allows obtaining PVDF with 100% of γ-phase. An increase of the real dielectric constant ε′, dielectric loss tan δ and AC conductivity was observed by increasing CNC content. More importantly, these values are further boosted upon CNC surface-modification, suggesting the pivotal role of the CNC–PVDF interface. We conclude that the sulfate half-ester removal increase the amount of exposed –OH groups with increase the amount of accumulated charges at the PVDF–CNC interfaces.

Cellulose emerges as a promising sustainable alternative to traditional polyolefin-based lithium-ion battery (LIB) separators because of its good mechanical properties and inherent hydrophilic character. Therefore, in this work we fabricate high specific surface area mesoporous cellulose nanocrystal (MCNC) membranes with different pore morphology as novel three-dimensional porous separators. N-2 adsorption-desorption isotherms and scanning electron microscopy (SEM) analyses reveal that membranes are composed of loosely packed cellulose nanocrystals (CNCs) with specific surface areas up to 172 m(2).g(-1) and porosities up to 75.3%. The prepared mesoporous separators show low contact angle values when evaluated against conventional electrolyte and ionic liquid, suggesting a pivotal role of the porous 3D structure on the resulting wettability, where mesopores provide efficient paths for Li+ ion migration through the membrane. Furthermore, the membranes show ionic conductivities of 2.7 mS.cm(-1), wide electrochemical stability, and good interfacial compatibility with the lithium electrode, delivering a specific capacity of 122 mAh.g(-1) and 85 mAh-g(-1) at a C/2 and 2C rate, respectively. On the basis of the displayed high discharge capacity, small overpotential, wide electrochemical window, and good cycling stability, the use of ionic liquids (ILs) as suitable electrolytes together with MCNC membranes for the development of environmentally friendly separator-electrolyte systems was also evaluated.

This work reports the development of renewable cellulose nanocrystal (CNC) and ionic liquid (IL) hybrid materials for bending actuator applications. For this purpose, cellulose nanocrystals with different surface charges (neutral, positive and negative) were prepared and increasing amounts of the IL 2-hydroxy-ethyl-trimethylammonium dihydrogen phosphate ([Ch][DHP]) (10 and 25 wt%) were incorporated into the CNC hosting matrix. The morphology of the samples was evaluated, proving that both surface charge and IL incorporation do not affect the characteristic layered structure of the CNC. Atomic force microscopy results reveal a sea-island morphology in the hybrid films, where CNC bundles are surrounded by [Ch][DHP]-rich regions. An increase in the electrical conductivity is observed upon IL incorporation into the CNC matrix, regardless of the CNC surface charge. The highest electrical conductivity values are observed for IL/CNC (+) 25 wt% with an electrical conductivity of 3.18 x 10(-5) +/- 2.75 x 10(-7) S cm(-1) and IL/CNC (-) 10 wt% (1.26 x 10(-5) +/- 5.92 x 10(-6) S cm(-1)). The highest bending displacement of 2.1 mm for an applied voltage of 4.0 Vpp at a frequency of 100 mHz was obtained for the IL/CNC (+) 25 wt% composite, demonstrating the suitability of cellulose to develop soft actuators.

This work reports on the development of polymer composites for load sensing applications. Three thermoplastic polymers, one with elastomeric behaviour, namely poly(styrene-butadiene-styrene) and poly(styrene–ethylene/butylene-styrene), and a semi-crystalline fluorinated polymer, poly(vinylidene fluoride), were selected as hosting matrices. In order to improve the sensing capacity, both ceramic nanoparticles (barium titanate, BT) and carbon nanotubes (CNTs) have been incorporated through solvent mixing followed by spreading the solution onto a glass substrate and subsequent solvent evaporation. Scanning electron microscopy results show that nanoparticles remain uniformly distributed through the nanocomposite at concentrations as high as 50% by weight. Polymer-filler interactions and thermal stability of the nanocomposites were assessed by Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively, in which these nanocomposites present physical interaction between constituents rather than chemical interaction and thermal stability increases slightly for larger filler contents. The mechanical properties are dependent on the matrix, filler type and amount in which the incorporation of both fillers in the elastomeric matrices increases the initial modulus of the nanocomposites up to 3-times. Electrically insulating BT increases dielectric properties and electrically conducting CNTs increase the dc conductivity of nanocomposites, respectively, and the combination of both fillers results in a synergetic effect. Finally, the changes induced by applied static loads on the capacitance variation (ΔC) of the nanocomposites were evaluated, showing a marked enhancement on the ΔC upon the incorporation of both fillers due to the synergetic effect provided by electrically insulating BT together with electrically conducting CNTs.

Rapid technological developments in biomedicine, sensors, actuators and energy areas are taken place in the context of the global digital transformation, supported by the “Industry 4.0″ and “Internet of Things” (IoT) concepts. Those developments must include circular economy considerations in the scope of the 2030 sustainable developments goals to ensure easy access to affordable, sustainable, reliable, and modern services for all. To fulfil these advances, materials with high-performance based on biopolymers with tailored dielectric, magnetic and conducting properties are needed for improving devices performance while reducing environmental impact. Within this scope, bio-based resources are considered as next-generation materials for a broader range of applications. In this context, we present on the molecular structure, organization, main physical-chemical and functional properties of the most promising biopolymers. Further, the various possible modifications and processing methods are discussed to reach specific morphological, structural and/or functional characteristics. Finally, bio polymers-based blends and composites are discussed, alongside with their main application areas, opportunities, and challenges.

Films based on poly(vinylidene fluoride) (PVDF) blended with ionic liquids (ILs) comprising different cations and anions were developed to investigate the IL influence on the resulting PVDF crystalline phase. Blends with 25 wt % IL content were produced by solvent casting followed by solvent evaporation at 210 °C in an air oven. Five different ILs containing the same cation 1-ethyl-3-methylimidazolium [Emim] and five ILs containing the same anion bis(trifluoromethylsulfonyl)imide [TFSI] were selected. The formation of the different phases and the resulting thermal and dynamic mechanical properties were studied by Fourier transform infrared spectroscopy, differential scanning calorimetry, and dynamic mechanical analysis. The incorporation of [Emim]-based ILs successfully directs the PVDF crystallization from the nonpolar α-phase toward the electroactive and highly polar β-phase. On the contrary, blends containing [TFSI] as a common anion yield a mixture of α and β phases. Overall, the induced β-phase ranges between 14 and 95% depending on the incorporated IL type. Interestingly, 1-ethyl-3-methylimidazolium chloride [Emim][Cl] is the most effective IL among the studied ones to significantly enhance the β-phase content, showing also a marked nucleating effect. The results suggest that ions favorably interact with PVDF chains and are located occupying the amorphous interlamellar PVDF regions. Furthermore, the studied ILs act as plasticizers, yielding lower glass-transition temperatures of the amorphous phase and decreasing mechanical storage modulus at room temperature.