Magnetic cellulose nanocrystal nanocomposites for

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Carbohydrate Polymers 175 (2017) 425–432

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Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol

Research Paper

Magnetic cellulose nanocrystal nanocomposites for the development of green functional materials E. Lizundia a,b,∗ , A. Maceiras c , J.L. Vilas b,c , P. Martins d , S. Lanceros-Mendez c,e a

Dept. of Graphic Design and Engineering Projects, Bilbao Faculty of Engineering, University of the Basque Country (UPV/EHU), Spain Macromolecular Chemistry Research Group (LABQUIMAC), Dept. of Physical Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Spain c BCMaterials, Parque Científico y Tecnológico de Bizkaia, 48160 Derio, Spain d Centro de Física, Universidade do Minho, 4710-057 Braga, Portugal e IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain b

a r t i c l e

i n f o

Article history: Received 25 May 2017 Received in revised form 4 July 2017 Accepted 5 August 2017 Available online 8 August 2017 Chemical compounds studied in this article: Cellulose (PubChem CID: 14055602) Sulphuric acid (PubChem CID: 1118) Sodium hydroxide (PubChem CID: 14798) Cobalt ferrite (PubChem CID: 44602546) Distilled water (PubChem CID: 962) Keywords: Cellulose nanocrystals Biopolymers Ferrites Electroactive materials Nanocomposites

a b s t r a c t A magnetic cellulosic material composed of cellulose nanocrystals (CNC) and cobalt ferrite (CoFe2 O4 ) 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 CoFe2 O4 nanoparticles produces a marked decrease in the amount of the transmitted light. 20 wt.% of CoFe2 O4 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. © 2017 Elsevier Ltd. All rights reserved.

1. Introduction Poly(vinylidene fluoride), PVDF, and its copolymers such as P(VDF-CTFE), poly(vinylidene fluoride-chlorotrifluoroethylene); P(VDF-HFP), poly(vinylidene fluoride-co-hexafluoropropene); P(VDF-TrFE), poly(vinylidene fluoride-trifluoroethylene) and P(VDF-TrFE-CTFE), poly(vinylidenefluoride/trifluoroethylene/ chlorotrifluoroethylene are the family of polymers that exhibit the highest dielectric constant and electroactive response, includ-

∗ Corresponding author at: Dept. of Graphic Design and Engineering Projects, Bilbao Faculty of Engineering, University of the Basque Country (UPV/EHU), Alameda Urquijo w/n, 48013 Bilbao, Spain. E-mail addresses: [email protected], [email protected] (E. Lizundia), [email protected] (A. Maceiras), [email protected] (J.L. Vilas), pmartins@fisica.uminho.pt (P. Martins), [email protected], lanceros@fisica.uminho.pt (S. Lanceros-Mendez). http://dx.doi.org/10.1016/j.carbpol.2017.08.024 0144-8617/© 2017 Elsevier Ltd. All rights reserved.

ing piezoelectric, pyroelectric and ferroelectric effects (Martins, Lopes, & Lanceros-Mendez, 2014). Such electroactive properties are increasingly important in a wide range of applications such as biomedicine, energy generation and storage, monitoring and control, and include the development of sensors and actuators, separator and filtration membranes and smart scaffolds, among others (Martins et al., 2014; Ribeiro, Sencadas, Correia, & LancerosMéndez, 2015). Particularly, the addition of magnetic nanoparticles into the PVDF matrix allows to obtain nanocomposites with exceptional magnetic responsive features. Such magnetic responsive polymer composites provide unique capabilities as it can be spatially and temporally controlled, and can be additionally operated externally to the system, providing a non-invasive approach to remote control (Thévenot, Oliveira, Sandre, & Lecommandoux, 2013). Nevertheless, due to the depletion of fossil resources, both industry and academia are now encouraged to find sustainable alternatives to replace the existing petro-based materials such

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as PVDF and its copolymers. It is reported that 140 million tons of petro-based polymers are discarded every year, which represents serious environmental risks (Rudnik, 2008). This trend is being further driven by recent environmental, political and administrative requirements. In this sense, materials from biological and natural origin are emerging as novel candidates to replace petroleum-based materials. Especially interesting are the materials from agro-waste origin, which represent a suitable alternative to produce biodegradable and renewable materials with lower energy consumption. Although polylactides (PLAs, starch-based polyesters) and polyhydroxyalkanoates (PHAs, polyesters naturally produced by bacterial fermentation) remain as some of the most popular naturally-derived polymers thanks to their biobased character, transparency, biodegradability, non-toxicity and mechanical properties (Auras, Harte, & Selke, 2004; Drumright, Gruber, & Henton, 2000; Lee, 1996a, 1996b), nowadays cellulosic materials show one of the largest potential to obtain novel functional materials because of the wide availability and low price. Cellulose ((C6 H10 O5 )n ) is considered as the major natural source of raw materials (it is the most commonly found biopolymer on earth) and is a carbohydrate composed by ␤-d-glucose units (Dufresne, 2013). Additionally, cellulose has been reported to exhibit electroactive properties (Kim, Yun, & Ounaies, 2006) that are increasingly important in a wide range of applications such as in biomedicine and the development of sensors and actuators, among others. From all the cellulosederived materials, cellulose nanocrystals (CNCs) are receiving an especial attention due to their physico-mechanical properties. CNCs are usually extracted from native cellulose after a controlled disintegration of cellulose (usually an acid-induced destructuring process (Dufresne, 2008; Habibi, Lucia, & Rojas, 2010)), which dissolves the amorphous regions to yield rod-like nanostructures with high mechanical stiffness (a reported modulus of elasticity of about 150 GPa) and low density of 1.57 g/cm3 (Habibi et al., 2010). To date, these innovative nanostructures have been employed to reinforce a hosting polymeric matrix (Lizundia, Vilas, & Le&n, 2015; Lizundia, Fortunati et al., 2016), as drug-delivery systems (Akhlaghi, Berry, & Tam, 2013), as colourful films for optical applications or for electronics (Lizundia, Delgado-Aguilar et al., 2016; Schlesinger, Hamad, & Maclachlan, 2015). Similar to petro-based polymers, the introduction of nanoparticles into CNC host may allow the development of multifunctional materials with improved properties. As an example, photoluminescent CNC films have been obtained after the co-assembly of carbon dots with CNCs at a concentration of 0.2 wt.% (Lizundia, Nguyen, Vilas, Hamad, & MacLachlan, 2017) while conductive photoswitchable structures based on cellulose were obtained by the incorporation of sol-gel synthesized vanadium nanoparticles (Tercjak, Gutierrez, Barud, & Ribeiro, 2016). From an industrial point of view, it results essential to develop a method that enables an easy incorporation of these functional nanoparticles into CNC matrix. So far, evaporation induced self-assembly (EISA) has been proven to be an energetically-efficient approach to develop homogeneous CNC-based nanohybrids with no need of grafting steps (Lizundia et al., 2017). Unfortunately, because of the capillary pressure gradients and condensation formed during the drying process, CNC-films trend to crack into centimetre-sized fragments, seriously limiting their practical application (Zarzycki, Prassas, & Phalippou, 1982). It is reported that this drawback could be faced by simply adding sugars during EISA (Kelly, Yu, Hamad, & Maclachlan, 2013), effectively improving the mechanical flexibility of cellulosic films without affecting their optical properties and microstructure. Moreover, magnetically responsive CNC composite materials have been investigated in medical applications (Xiong, Lu, Wang, Zhou, & Zhang, 2013) transparent films, (Li et al., 2013), electrospun polyvinyl alcohol (PVA)-CNC composite fibres (Nypelö,

Rodriguez-Abreu, Rivas, Dickey, & Rojas, 2014), and aerogels (Guo et al., 2017; Olsson et al., 2010). Due to the magnetic and dielectric properties of ferrites, much interest has been focused on polymer-based composites filled with ferrite nanoparticles, such as cobalt-ferrite and nickel-ferrite, for their applicability in areas such as electromagnetic wave absorption, bio-separation, and diagnostics. Several authors have indeed reported the development of magnetic cellulosic nanocomposites based mainly in Fe3 O4 nanoparticles, although other approaches could be also envisaged (Cao, Li, Lou, & Zong, 2014; Cao, Xu, Li, X. Lou, & Zong, 2015; Lu, Jin, Liu, Wang, & Cuyang, 2016; Low, Tey, Ong, Chan, & Tang, 2017). Their magnetostrictive properties also make them good candidates for magnetoelectric composites (Martins et al., 2012). The development of cellulose-based magnetoactive composites through the introduction of inorganic nanoparticles is a versatile strategy to obtain functional materials from agro-waste resources that could exploit the potential synergy of the combined organic-inorganic materials. The present work reports on the straightforward and inexpensive fabrication of CNC/CoFe2 O4 films through EISA using water as dispersing agent. CoFe2 O4 nanoparticles were chosen due to their highest magnetostriction (≈200 ppm) and high magnetization (60 emu g−1 ) among ferrite nanoparticles (Martins, Kolen’ko, Rivas, & Lanceros-Mendez, 2015).

2. Materials and methods 2.1. Starting materials Microcrystalline cellulose with a particle size of 20 ␮m (310697500G), sulphuric acid and glucose (d-(+)-Glucose, G5767-500G) have been supplied by Sigma Aldrich. Cobalt ferrite (CoFe2 O4 ) nanoparticles were purchased from Nanoamor and their magnetization characteristics can be found in literature (Gonc¸alves et al., 2015).

2.2. Cellulose nanocrystals (CNCs) synthesis Cellulose nanocrystals (CNCs) were obtained by sulphuric acid hydrolysis of microcrystalline cellulose (Lizundia et al., 2015). Cellulose was hydrolyzed with 64% (w/w) sulphuric acid solution at 45 ◦ C for 30 min with constant stirring. The reaction was quenched by adding 20-fold distilled water. The resulting suspension was centrifuged several times at 4000 rpm for 15 min to concentrate the remaining cellulose and to remove excess aqueous acid. Nanocellulose was obtained by sonication into a Vibracell Sonicator (Sonics and Materials Inc., Danbury, CT) at 50% output for 15 min. Finally, the suspension was dialyzed for 15 days to obtain aqueous CNC dispersion with a pH of 1.9 and a concentration of 2 wt.%.

2.3. Nanocomposite film fabrication Nanocomposites were prepared by solvent evaporation method as previously reported for CNC/ZnO films (Lizundia, Urruchi, Vilas, & Le&n, 2016). Firstly, the proper amount of cobalt ferrite nanoparticles were dispersed in distilled water via ultrasonication for 10 min. If required, glucose was added (to yield nanocomposites having 20 wt.%) and the mixture was ultrasonicated for further 10 min. Subsequently, water-dispersed CNCs were added to obtain nanocomposites with concentrations of 0, 5, 10 and 20 wt.% and the dispersion was further ultrasonicated. Finally, solutions were casted in 75 mm diameter Petri-dishes and they were allowed to dry at room temperature for 72 h. Neat CNC film was also prepared for comparison. 30 ␮m films were obtained.

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2.4. Morphological characterization

The imaginary part of the dielectric function obtained from Eq. (2):

Cellulose nanocrystals have been analyzed by transmission electron microscopy (TEM). A suspension of CNC or CoFe2 O4 at 0.1% (w/w) in distilled water was deposited on a carbon-coated grid and after water evaporation TEM was carried out using a Philips CM120 Biofilter apparatus at an acceleration voltage of 120 kV. On the contrary, the morphology of nanocomposite films materials has been studied in a Hitachi S-4800 field emission scanning electron microscope (FE-SEM) at an acceleration voltage of 5 kV. Cryogenically fracture surfaces were gold-coated (10 nm thick coating) in an Emitech K550X sputter coater.

␧ = tan ı × ␧

2.5. Fourier transform infrared spectroscopy (FTIR) Infrared spectra in attenuated total reflectance (ATR) mode were recorded on a Shimadzu FTIR-8400S spectrophotometer using a MIRacle ZnSe ATR accessory. 32 scans were taken in the 600–4000 cm−1 with a 2 cm−1 resolution. 2.6. Wide angle X-ray diffraction (WAXD) Room temperature wide angle X-ray diffraction (WAXD) has been conducted in a PHILIPS X’PERT PRO automatic diffractometer in theta–theta configuration, secondary monochromator with Cu- K␣ radiation (␭ = 1.5418 Å) and a PIXcel solid state detector. The sample was mounted on a zero background silicon wafer fixed in a generic sample holder. Data were collected from 20 to 75◦ 2␪ (step size = 0.026◦ ). 2.7. UV–vis spectroscopy UV–vis absorption spectra were recorded with a Shimadzu MultiSpec-1501 spectrophotometer. Total transmittance experiments have been analyzed in the range of 200–800 nm with a sampling interval of 1 nm and 25 accumulations. 2.8. Thermogravimetric analysis Thermal stability of the materials was studied in a TGA METTLER TOLEDO 822e Thermal Gravimetric Analysis (TGA) instrument by heating the samples from room temperature to 700 ◦ C at 10 ◦ C/min under N2 atmosphere. 2.9. Vibrating sample magnetometer (VSM) Magnetic hysteresis loops were measured at room temperature using an ADE 3473-70 Technologies vibrating sample magnetometer (VSM) from −10,000 Oe to 10,000 Oe with a magnetization error of ±1%. 2.10. Dielectric measurements Dielectric measurements were performed with an automatic Quadtech 1929 Precision LCR meter. The applied signal for frequencies in the range 1 Hz–1 MHz was 0.5 V. The samples were coated with silver circular electrodes of 5 mm diameter onto both sides of the sample by magnetron sputtering SC502 sputter coater. The real part of the dielectric constant, ␧×, was calculated from the capacity (C) measurements taking into account the geometry of the sample, thickness (d) and area (A) (Eq. (1)). ε

=

C ×d A

(1)

(2)

3. Results and discussion 3.1. Morphological examination of starting materials and nanocomposite films As calculated from the TEM images depicted in Fig. 1a and b, synthesized CNCs and CoFe2 O were 141 ± 27 nm long and ∼10 nm wide and 35–60 nm in diameter respectively (statistics based on count of at least 50 particles using Image J software). FTIR spectra in Fig. 1c shows the characteristic conformational features of cellulose nanocrystals and CoFe2 O nanoparticles, both of them presenting a broad band in the 3650–3200 cm−1 region and narrower bands in the 1800–800 cm−1 region (Li et al., 2010; Lizundia et al., 2015). The WAXD pattern of CNCs in Fig. 1d displays two broad peaks at 14.9 and 22.7◦ attributed to the (110) and (200) planes of the cel˜ lulose I structure (Silva & Oliveira, 2016; Goikuria, Larranaga, Vilas, & Lizundia, 2017), while in the diffraction pattern of CoFe2 O ferrite nanoparticles an inverse cubic spinel structure with space group Fd-3m is observed (Martins et al., 2015). The narrow sharp peaks corresponding to (220), (311), (400), (511) and (440) planes reveal the high purity of the used ferrites and no peaks corresponding to impurities were detected. As shown in Fig. 2, the morphology of the prepared large and rack-free nanocomposite films (see Fig. S1 for their macroscopic appearance) was investigated by field emission scanning electron microscopy (FE-SEM). A look to the fractured edge normal to the film surfaces reveals that the addition of glucose and cobalt ferrite nanoparticles does not substantially modify the original structure of neat CNC film. Therefore, the introduction of a simple sugar, glucose, into CNC network allows the development of homogeneous crack-free CNC-based films, which may result useful for applications such as sensors, printing electronics or electroactive transducers. Additionally, all cross-section FE-SEM micrographs reveal that CNCs assemble into a layered structure independently on the amount of added CoFe2 O4 . Moreover, higher magnification images in Fig. S2 do not show the presence of aggregates, indicating that CoFe2 O4 nanoparticles remain well intercalated within the layered structure of CNCs, allowing thus the long-range ordering of original CNCs (Dumanli et al., 2014). This homogeneous distribution of cobalt ferrite nanoparticles into CNC film has been obtained thanks to the co-assembly of CoFe2 O4 together with CNCs during the evaporation induced self-assembly (EISA), which has been proven to allow the development of homogeneous nanocomposites with no need of surfactants (Lizundia et al., 2017; Xu, Nguyen, Xie, Hamad, & MacLachlan, 2015). 3.2. UV–vis spectroscopy The UV–vis (ultraviolet–visible) transmittance of CNC/CoFe2 O4 and CNC/glucose/CoFe2 O4 nanocomposite films in the 200–800 nm region (ultraviolet and visible) has been evaluated by UV–vis spectroscopy (Fig. 3). As determined by the ASTM D1746-03 standard, neat CNC film presents an optical transparency of 26% (the transmittance in the 540–560 nm range), which is decreased up to 19% upon glucose addition. This transparency decrease is due to the mismatch in the refractive indexes n of cellulose nanocrystals (nCNC ≈ 1.56) and glucose (nglucose ≈ 1.32–1.36 depending on the concentration) (Cranston & Gray, 2008; Yeh, 2008), which results in enhanced light scattering through the nanocomposite film (Lin, Day, & Stoffer, 2004). It could be further noticed that the films with no nanoparticles (neat CNC and CNC/glucose films) present

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Fig. 1. Representative transmission electron microscopy (TEM) images showing synthesized cellulose nanocrystals (a) and commercial CoFe2 O4 nanoparticles (b). FTIR spectra (c) and WAXD patterns (d) of raw CNC and CoFe2 O4 .

Fig. 2. Representative FE-SEM images of fractured surfaces at different nanoparticle concentration for both CNC/CoFe2 O4 and CNC/glucose/CoFe2 O4 nanocomposite films: (a) neat CNC; (b) CNC/CoFe2 O4 5 wt.%; (c) CNC/CoFe2 O4 10 wt.%; (d) CNC/CoFe2 O4 20 wt.%; (e) CNC/glucose; (f) CNC/glucose/CoFe2 O4 5 wt.%; (g) CNC/glucose/CoFe2 O4 10 wt.% and (h) CNC/glucose/CoFe2 O4 20 wt.%.

a reflectance peak which maximum is located at 479 nm, which is associated to the long-range chiral nematic structure of CNCs already observed by SEM in Fig. 2 (Lizundia et al., 2017). Therefore, it could be concluded that the introduction of glucose into CNC films does not modify neither the morphology nor the optical properties (assessed by SEM and UV–vis spectroscopy respectively). Overall, the introduction of CoFe2 O4 nanoparticles within the layered structure of CNC film produces a marked decrease in the amount of the transmitted UV and visible light to yield films whose transparency is about ∼2%. As a result of its electronic structure, cobalt ferrite

strongly absorbs light in the 200–800 nm region and does not allow light to pass through in the whole UV and visible range, yielding optically black films. 3.3. Magnetic and dielectric studies In order to explore the potential of CNC/CoFe2 O4 films for the development of magnetoelectric composites, the magnetization of cellulose-based films was determined by VSM technique at room temperature. As it can be observed in Fig. 4, for all sam-

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Fig. 3. UV–vis spectroscopy of for CNC/CoFe2 O4 and CNC/glucose/CoFe2 O4 nanocomposite films.

ples the magnetization increases with increasing the magnetic field until saturation. The hysteresis loops of the composite films reveal a coercivity of ≈0.25 T. It should be noticed that for the CoFe2 O4 nanoparticles, room temperature is below the blocking temperature and the magnetic moment of the particles is not free to rotate in response to the applied magnetic field (Martins & Lanceros-Méndez, 2013). Additionally, the shape and maximum magnetization values of the measured hysteresis loops for the composite samples demonstrate that magnetic particles are randomly oriented within the cellulose matrix. The magnetization saturation increases with increasing filler content (see Fig. 4b) for both compositions being maximized to 12.96 emu g−1 and 8.47 emu g−1 for the composites having 20 wt.% of ferrite nanoparticles with cellulose/glucose and cellulose respectively. It is important to note that the addition of glucose into CNC/CoFe2 O4 films does not only reduce the inherent brittleness of CNC films (Kelly et al., 2013), but also contributes to the enhancement of magnetization saturation. As depicted in Fig. 5, the evolution of real and imaginary parts of the dielectric constant has been also measured for all the prepared composition range. It is observed that the value of the dielectric constant decreases with increasing frequency. The pronounced decrease with increasing frequency up to ≈10 kHz can be attributed to the trend of dipoles in the macromolecules to orient themselves in the direction of the applied field when the applied frequency is low enough. By increasing frequency, the dipoles are not able to follow the applied field and reorient in the direction of the applied field in each cycle, leading to a decrease of the dielectric constant (Reddy, Kumar, & Rao, 1993). The first effect of the inclusion of CoFe2 O4

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nanoparticles within the cellulose matrix is to slightly reduce the dielectric response of neat CNC film, and the resulting composite films only recover the permittivity and loss tangent of the pure polymer for filler contents of 10 wt.% and above Li et al. (2011). Thus, at low filler concentrations, magnetic fillers act as a defect locally hindering dipolar dynamic and leading to a decrease of the dielectric constant (Kochetov, Andritsch, Morshuis, & Smit, 2012). For higher filler contents, the increase of the local ionic conductivity and interfacial polarization contributions (Maxwell-Wagner contributions) lead to the small increase in the dielectric response (Martins, Silva, Silva, & Lanceros-Mendez, 2016). The addition of glucose into CNC/CoFe2 O4 films seems to have only effect on the dielectric response of the composite films with 10 wt.% of ferrite nanoparticles. The increase in dielectric constant of the three-phase composite (CNC/glucose/CoFe2 O4 ) is most likely due to enhanced ionic conductivity related to the well dispersed CoFe2 O4 and glucose inside the cellulose matrix and to the interfacial polarization effects (Wang, 2010). Such very good distribution and interface polarization can be impaired to higher ferrite contents, due the agglomerations (reduction of the effective interface area), leading to a dielectric response in the two-phase composites (CNC/CoFe2 O4 ) very similar to the one of the three phase composites (CNC/glucose/CoFe2 O4 ). To inferior ferrite contents the interface value is much lower leading once again to a dielectric response in the two-phase composites (CNC/CoFe2 O4 ) comparable to the one obtained in the three phase composites (CNC/glucose/CoFe2 O4 ) (Gonc¸alves et al., 2015). In short, the optimized concentration regarding the formation of polymer/particle interface is 10 wt.% of ferrite nanoparticles; higher, or lower concentrations will lead to a decrease in the interface area and as a consequence a decrease in the dielectric response of the CNC/glucose/CoFe2 O4 composite, reaching a similar response observed in the two-phase CNC/CoFe2 O4 films. 3.4. Thermal stability In view to determine the maximum operating temperature of CNC/CoFe2 O4 nanocomposites, thermogravimetric analysis (TGA) has been conducted as it allows defining the thermal stability of materials. Fig. 6a and b show the thermogravimetric traces and weight loss rates of CNC/CoFe2 O4 films respectively, while Table 1 summarizes obtained representative thermodegradation parameters. Because of the depolymerization, dehydration and decomposition of cellulose gyclosyl units induced by the temperature increase (Roman & Winter, 2004), neat CNC film begins to degrade at 165.1 ◦ C (Tonset , as determined by the first 10 wt.% loss), reaches its maximum degradation rate at 169.2 ◦ C (Tpeak ) with a

Fig. 4. (a) Room temperature hysteresis loops for the CNC/glucose/CoFe2 O4 nanocomposite films; (b) Saturation Magnetization (MagnetizationSAT ) value at 10,000 Oe as a function of the weight fraction of magnetic nanoparticles within the composite films, obtained from the hysteresis loops.

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Fig. 5. (a) Frequency dependence of the real part of the permittivity for the different CNC/glucose/CoFe2 O4 nanocomposite films. (b) Real and imaginary parts of the dielectric constant, both measured at 1 kHz, as a function of the weight fraction of cobalt ferrite.

Fig. 6. TGA (a) and DTG (b) traces of CNC/CoFe2 O4 and CNC/glucose/CoFe2 O4 nanocomposites. Table 1 Characteristic thermodegradation temperatures (Tonset and Tpeak ), maximum degradation rates (DTGmax ) of CNC/CoFe2 O4 and CNC/glucose/CoFe2 O4 nanocomposites. Sample

Tonset (◦ C)

Tpeak (◦ C)

DTGmax (◦ C)

CNC CNC/CoFe2 O4 5 wt.% CNC/CoFe2 O4 10 wt.% CNC/CoFe2 O4 20 wt.% CNC/glucose CNC/glucose/CoFe2 O4 5 wt.% CNC/glucose/CoFe2 O4 10 wt.% CNC/glucose/CoFe2 O4 20 wt.%

165.1 176.2 185.1 220.4 161.3 181.6 182.1 218.7

169.2 175.3/222.7 177.3/231.2 183.1/254.9 170.1 171.5/240.3 180.3/228.8 192.2/263.6

−0.76 −0.45/−0.28 −0.29/−0.31 −0.13/−0.31 −0.68 −0.25/−0.32 −0.23/−0.28 −0.09/−0.35

increased thermal stability is in line with the findings reported for CNC/ZnO, CNC/Fe2 O3 and CNC/Al2 O3 and may be related to two effects (Goikuria et al., 2017; ; Lizundia et al., 2016). First of all, cobalt ferrite behaves as a flame-retardant when temperature is increased (Ul-Islam, Khattak, Ullah, Khan, & Park, 2014). Secondly, these nanoparticles interact with their surrounding environment to provide barriers for the permeation of combustion gas, delaying the whole thermodegradation process (Liu, Walther, Ikkala, Belova, & Berglund, 2011).

4. Conclusions maximum degradation rate (DTGmax ) of −0.76. The addition of glucose to CNCs decreases the thermal stability of the resulting material by ≈3 ◦ C due to the slightly less thermal stability of glucose when comparing with CNCs (note that smaller char residue is obtained due to the carbonization of the glucose phase into CNC/glucose composite) (Ma et al., 2014). Overall, the thermodegradation process of nanocomposites is continuously delayed upon the addition of CoFe2 O4 at the same time that DTGmax is markedly reduced notably (char residue increases because cobalt ferrite nanoparticles do not suffer any weight loss in the studied temperature range). The two-stage thermodegradation process occurring in CNC and CNC/glucose films is shifted to a three-stage process as noticed by the presence of three maximums in the DTG curve (Fig. 4b), implying that the presence of CoFe2 O4 modify the thermodegradation mechanism of CNCs. This

In this work we introduce cobalt ferrite (CoFe2 O4 ) nanoparticles into cellulose nanocrystal (CNC) films to develop green nanocomposite materials with magnetic properties. Further, the effect of introducing glucose was evaluated to obtain large crack-free films and enable their prospective application. It is observed that the addition of glucose and cobalt ferrite nanoparticles does not substantially modify the original layered structure of neat CNC film and that the cobalt ferrite nanoparticles decrease the optical transparency and increase the onset degradation temperature from 165.1 ◦ C to 220.4 ◦ C of the CNC matrix. The effect of the filler concentration on the dielectric and magnetic response of the composites reveal a maximum magnetization value of 12.96 emu g−1 and an increased the real part of the dielectric constant from 10 (pure polymer) to 12 for the composite with 20 wt.% of ferrite nanoparticles. Overall, the results prove the suitability of these materials for the

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development of nanostructured bio-based magnetoactive polymer composites. Acknowledgements Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, EGEF and ESF) is gratefully acknowledged. Authors thank the Basque Country Government for financial support (IT71813). The authors also thank the Portuguese Fundac¸ão para a Ciência e Tecnologia (FCT) for financial support under Strategic Funding UID/FIS/04650/2013 and project PTDC/EEI-SII/5582/2014, including FEDER funds, UE. P. Martins acknowledges also support from FCT (SFRH/BPD/96227/2013 grant). Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support) and from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged. The authors thank Y. V. Kolen’Ko, from the INLInternational Iberian Nanotechnology Laboratory, Braga, Portugal for his support in the magnetic evaluation of the samples. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.carbpol.2017.08. 024. References Akhlaghi, S. P., Berry, R. C., & Tam, K. C. (2013). Surface modification of cellulose nanocrystal with chitosan oligosaccharide for drug delivery applications. Cellulose, 20(4), 1747–1764. Auras, R., Harte, B., & Selke, S. (2004). An overview of polylactides as packaging materials. Macromolecular Bioscience, 4(9), 835–864. Cao, S. L., Li, X. H., Lou, W. Y., & Zong, M. H. (2014). Preparation of a novel magnetic cellulose nanocrystal and its efficient use for enzyme immobilization. Journal of Materials Chemistry B, 2, 5522–5530. Cao, S. L., Xu, H., Li, X. H., Lou, W. Y., & Zong, M. H. (2015). Papain@Magnetic nanocrystalline cellulose nanobiocatalyst: A highly efficient biocatalyst for dipeptide biosynthesis in deep eutectic solvents. ACS Sustainable Chemistry and Engineering, 3(7), 1589–1599. Cranston, E. D., & Gray, D. G. (2008). Birefringence in spin-coated films containing cellulose nanocrystals. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 325(1–2), 44–51. Drumright, R. E., Gruber, P. R., & Henton, D. E. (2000). Polylactic acid technology. Advanced Materials, 12(23), 1841–1846. Dufresne, A. (2008). Polysaccharide nano crystal reinforced nanocomposites. Canadian Journal of Chemistry, 86(6), 484–494. Dufresne, A. (2013). Nanocellulose: A new ageless bionanomaterial. Materials Today, 16(6), 220–227. Dumanli, A. G., Van Der Kooij, H. M., Kamita, G., Reisner, E., Baumberg, J. J., Steiner, U., et al. (2014). Digital color in cellulose nanocrystal films. ACS Applied Materials and Interfaces, 6(15), 12302–12306. ˜ Goikuria, U., Larranaga, A., & Vilas, J. L. (2017). Thermal stability increase in metallic nanoparticles-loaded cellulose nanocrystal nanocomposites. Carbohydrate Polymers, 171, 193–201. http://dx.doi.org/10.1016/j.carbpol.2017.05.024 Gonc¸alves, R., Martins, P., Correia, D. M., Sencadas, V., Vilas, J. L., León, L. M., et al. (2015). Development of magnetoelectric CoFe2O4/poly(vinylidene fluoride) microspheres. RSC Advances, 5(45), 35852–35857. Guo, J., Filpponen, I., Johansson, L.-S., Mohammadi, P., Latikka, M., Linder, M. B., et al. (2017). Complexes of magnetic nanoparticles with cellulose nanocrystals as regenerable, highly efficient, and selective platform for protein separation. Biomacromolecules, 18(3), 898–905. Habibi, Y., Lucia, L. A., & Rojas, O. J. (2010). Cellulose nanocrystals: Chemistry, self-assembly, and applications. Chemical Reviews, 110(6), 3479–3500. Kelly, J. A., Yu, M., Hamad, W. Y., & Maclachlan, M. J. (2013). Large, crack-free freestanding films with chiral nematic structures. Advanced Optical Materials, 1(4), 295–299. Kim, J., Yun, S., & Ounaies, Z. (2006). Discovery of cellulose as a smart material. Macromolecules, 39(12), 4202–4206. Kochetov, R., Andritsch, T., Morshuis, P. H. F., & Smit, J. J. (2012). Anomalous behaviour of the dielectric spectroscopy response of nanocomposites. IEEE Transactions on Dielectrics and Electrical Insulation, 19(1), 107–117. Lee, S. Y. (1996a). Bacterial polyhydroxyalkanoates. Biotechnology and Bioengineering, 49(1), 1–14.

431

Lee, S. Y. (1996b). Plastic bacteria? Progress and prospects for polyhydroxyalkanoate production in bacteria. Trends in Biotechnology, 14(11), 431–438. Li, X. H., Xu, C. L., Han, X. H., Qiao, L., Wang, F. S., & Li, T. M. (2010). Synthesis and magnetic properties of nearly monodisperse CoFe2 O4 nanoparticles through a simple hydrothermal condition. Nanoscale Reserach Letters, 5, 1039–1044. Li, Y., Huang, X., Hu, Z., Jiang, P., Li, S., & Tanaka, T. (2011). Large dielectric constant and high thermal conductivity in poly(vinylidene fluoride)/barium titanate/silicon carbide three-phase nanocomposites. ACS Applied Materials & Interfaces, 3(11), 4396–4403. Li, Y., Zhu, H., Gu, H., Dai, H., Fang, Z., Weadock, N. J., et al. (2013). Strong transparent magnetic nanopaper prepared by immobilization of Fe3O4 nanoparticles in a nanofibrillated cellulose network. Journal of Materials Chemistry A, 1(48), 15278–15283. Lin, H., Day, D. E., & Stoffer, J. O. (2004). Optical and mechanical properties of optically transparent poly(methyl methacrylate) composites. Polymer Engineering & Science, 32(5), 344–350. Liu, A., Walther, A., Ikkala, O., Belova, L., & Berglund, L. A. (2011). Clay nanopaper with tough cellulose nanofiber matrix for fire retardancy and gas barrier functions. Biomacromolecules, 12(3), 633–641. Lizundia, E., Vilas, J. L., & León, L. M. (2015). Crystallization, structural relaxation and thermal degradation in poly(l-lactide)/cellulose nanocrystal renewable nanocomposites. Carbohydrate Polymers, 123, 256–265. Lizundia, E., Nguyen, T. D., Vilas, J. L., Hamad, W. Y., & MacLachlan, M. J. (2017). Chiroptical luminescent nanostructured cellulose films. Materials Chemistry Frontiers, 1(5), 979–987. Lizundia, E., Delgado-Aguilar, M., Mutjé, P., Fernandez, E., Robles-Hernandez, B., Rosario de la Fuente, M., et al. (2016). Cu-coated cellulose nanopaper for green and low-cost electronics. Cellulose, 23(3), 1997–2010. Lizundia, E., Fortunati, E., Dominici, F., Vilas, J. L., León, L. M., Armentano, I., et al. (2016). PLLA-grafted cellulose nanocrystals: Role of the CNC content and grafting on the PLA bionanocomposite film properties. Carbohydrate Polymers, 142, 105–113. Lizundia, E., Urruchi, A., Vilas, J. L., & León, L. M. (2016). Increased functional properties and thermal stability of flexible cellulose nanocrystal/ZnO films. Carbohydrate Polymers, 136, 250–258. Low, L. E., Tey, B. T., Ong, B. H., Chan, E. S., & Tang, S. Y. (2017). Palm olein-in-water Pickering emulsion stabilized by Fe3 O4 -cellulose nanocrystal nanocomposites and their responses to pH. Carbohydrate Polymers, 155, 391–399. Lu, J., Jin, R. N., Liu, C., Wang, Y. F., & Cuyang, X. K. (2016). Magnetic carboxylated cellulose nanocrystals as adsorbent for the removal of Pb(II) from aqueous solution. International Journal of Biological Macromolecules, 93, 547–556. Ma, Z., Zhang, H., Yang, Z., Zhang, Y., Yu, B., & Liu, Z. (2014). Highly mesoporous carbons derived from biomass feedstocks templated with eutectic salt ZnCl2 /KCl. Journal of Materials Chemistry A, 2(45), 19324–19329. Martins, P., & Lanceros-Méndez, S. (2013). Polymer-based magnetoelectric materials. Advanced Functional Materials, 23(27), 3371–3385. Martins, P., Costa, C. M., Botelho, G., Lanceros-Mendez, S., Barandiaran, J. M., & Gutierrez, J. (2012). Dielectric and magnetic properties of ferrite/poly(vinylidene fluoride) nanocomposites. Materials Chemistry and Physics, 131(3), 698–705. Martins, P., Lopes, A. C., & Lanceros-Mendez, S. (2014). Electroactive phases of poly(vinylidene fluoride): Determination, processing and applications. Progress in Polymer Science, 39(4), 683–706. Martins, P., Kolen’ko, Y. V., Rivas, J., & Lanceros-Mendez, S. (2015). Tailored magnetic and magnetoelectric responses of polymer-based composites. ACS Applied Materials & Interfaces, 7(27), 15017–15022. Martins, P., Silva, D., Silva, M. P., & Lanceros-Mendez, S. (2016). Improved magnetodielectric coefficient on polymer based composites through enhanced indirect magnetoelectric coupling. Applied Physics Letters, 109(11), 112905. Nypelö, T., Rodriguez-Abreu, C., Rivas, J., Dickey, M. D., & Rojas, O. J. (2014). Magneto-responsive hybrid materials based on cellulose nanocrystals. Cellulose, 21(4), 2557–2566. Olsson, R. T., Azizi Samir, M. A. S., Salazar-Alvarez, G., Belova, L., Ström, V., Berglund, L. A., et al. (2010). Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates. Nature Nanotechnology, 5(8), 584–588. Reddy, N. V., Kumar, C. R., & Rao, V. V. R. N. (1993). Dielectric properties of amorphous cellulose acetate-butyrate polymer films. Polymer International, 32(4), 381–384. Ribeiro, C., Sencadas, V., Correia, D. M., & Lanceros-Méndez, S. (2015). Piezoelectric polymers as biomaterials for tissue engineering applications. Colloids and Surfaces B: Biointerfaces, 136, 46–55. Roman, M., & Winter, W. T. (2004). Effect of sulfate groups from sulfuric acid hydrolysis on the thermal degradation behavior of bacterial cellulose. Biomacromolecules, 5(5), 1671–1677. Rudnik, E. (2008). Compostable Polymer Materials. Chapter 8 – Environmental impact of compostable polymer materials, 182–199. Schlesinger, M., Hamad, W. Y., & Maclachlan, M. J. (2015). Optically tunable chiral nematic mesoporous cellulose films. Soft Matter, 15, 4686–4694. Silva, R. P., & Oliveira, R. V. B. (2016). Non-isothermal degradation kinetics andmorphology of PP/TiO2 nanocomposites using titanium n-butoxide precursor. International Journal of Plastics Technology, 20(2), 364–377. Tercjak, A., Gutierrez, J., Barud, H. S., & Ribeiro, S. J. L. (2016). Switchable photoluminescence liquid crystal coated bacterial cellulose films with conductive response. Carbohydrate Polymers, 143, 188–197.

432

E. Lizundia et al. / Carbohydrate Polymers 175 (2017) 425–432

Thévenot, J., Oliveira, H., Sandre, O., & Lecommandoux, S. (2013). Magnetic responsive polymer composite materials. Chemical Society Reviews, 42(17), 7099–7116. Ul-Islam, M., Khattak, W. A., Ullah, M. W., Khan, S., & Park, J. K. (2014). Synthesis of regenerated bacterial cellulose-zinc oxide nanocomposite films for biomedical applications. Cellulose, 21(1), 433–447. Wang, G. (2010). Enhanced dielectric properties of three-phase-percolative composites based on thermoplastic-ceramic matrix (BaTiO3 + PVDF) and ZnO radial nanostructures. ACS Applied Materials & Interfaces, 2(5), 1290–1293. Xiong, R., Lu, C., Wang, Y., Zhou, Z., & Zhang, X. (2013). Nanofibrillated cellulose as the support and reductant for the facile synthesis of Fe3 O4 /Ag nanocomposites with catalytic and antibacterial activity. Journal of Materials Chemistry A, 1(47), 14910–14918.

Xu, J., Nguyen, T. D., Xie, K., Hamad, W. Y., & MacLachlan, M. J. (2015). Chiral nematic porous germania and germanium/carbon films. Nanoscale, 7(31), 13215–13223. Yeh, Y. L. (2008). Real-time measurement of glucose concentration and average refractive index using a laser interferometer. Optics and Lasers in Engineering, 46(9), 666–670. Zarzycki, J., Prassas, M., & Phalippou, J. (1982). Synthesis of glasses from gels: The problem of monolithic gels. Journal of Materials Science, 17(11), 3371–3379.