Basque Center for Materials

Derio, Spain

Basque Center for Materials

Derio, Spain
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Lizundia E.,University of the Basque Country | Vilas J.L.,University of the Basque Country | Vilas J.L.,Basque Center for Materials | Sangroniz A.,University of the Basque Country | Etxeberria A.,University of the Basque Country
European Polymer Journal | Year: 2017

Herein we attempt to provide a deeper understanding on the influence of metal oxide nanoparticle incorporation on the gas transport properties of resulting polymer-based nanocomposites. Polylactide has been used as a model biodegradable material to develop nanocomposites containing 1 v/v% of TiO2, SiO2, Fe2O3 and Al2O3 spherical particles. These nanoparticles were characterized by transmission electron microscopy (TEM), X-ray and ζ-potential measurements. Thermal properties of nanocomposites were analyzed by differential scanning calorimetry (DSC), while scanning electron microscopy (SEM) has been used to correlate nanoparticle dispersion with both light and gas barrier properties. UV–Vis spectroscopy indicates a good UV-shielding performance of developed films. Water vapour transmission rate and oxygen permeability of nanocomposites were further determined and obtained results have been correlated to the effect of interactions between the incorporated nanoparticles and water/oxygen molecules. Taking into account that only 1% of nanoparticles have been added, noticeable improvement of the barrier character of polylactide to water vapour, up to 18%, and wet oxygen, up to 9%, have been observed. Finally, Maxwell, Bruggeman, Böttcher and Higuchi models have been applied for our two-phase mixed matrix membranes to predict the permeability of dry oxygen. Overall, the experimental findings here shown provide better understanding towards the design of membrane devices based on biodegradable materials with tailored light and gas permeability for specific industrial applications. © 2017 Elsevier Ltd

Lizundia E.,University of the Basque Country | Makwana V.A.,University of Edinburgh | Larranaga A.,University of the Basque Country | Vilas J.L.,University of the Basque Country | And 2 more authors.
Polymer Chemistry | Year: 2017

The novel biodegradable aromatic-aliphatic polyester, poly(2-(2-hydroxyethoxy)benzoate), was explored through thermal analysis, X-ray diffraction, dynamic mechanical analysis and comparative bio and catalysed degradation. The polyester is a product of ring opening polymerisation (ROP) of 2,3-dihydro-5H-1,4-benzodioxepin-5-one catalysed by an aluminium salen catalyst. Thermal and mechanical characterisation showed that the polyester had a Tg of nearly 27 °C and crystallisation ability when cooled from melt, providing insight into potential biomedical and compatibiliser applications. These thermal and mechanical properties can be tuned by altering the polymer's molecular weight. The crystal structure has also been determined through wide-angle X-ray diffraction (WAXD). The polymer can be enzymatically degraded, but this process is slow compared to the rapid degradation by exploiting the monomer-polymer equilibrium catalysed by the aforementioned aluminium salen complex. © The Royal Society of Chemistry 2017.

Perez-Alvarez L.,University of the Basque Country | Perez-Alvarez L.,Basque Center for Materials | Laza J.M.,University of the Basque Country | Alvarez-Bautista A.,New University of Lisbon | Alvarez-Bautista A.,Institute Biologia Experimental e Tecnologica iBET
Current Pharmaceutical Design | Year: 2016

Chitosan nanogels present a very interesting combination of valuable characteristics for drug delivery; those derived from their nanometric size, such as, large surface area, rapid stimuli-response, and easy functionalization; and those emerged especially from their biocompatibility, biodegradability and mucoadhesive nature. Due to this, chitosan nanogels have reached a prominent position as nanocarriers and have originated accelerated research worldwide. Diverse methods to prepare chitosan nanogels have been reported, showing a dependence on final swelling, drug encapsulation capability and release properties with different synthesis variables, in such a way that they can be exploited to be modulated. The present review describes the properties of chitosan nanogels, along with the different methods of crosslinking and confining chitosan in nanosized particles, and the various fields of drug delivery where they have been applied. This work aims to emphasize the connection between the characteristics of chitosan and the synthetic variables with the final properties of chitosan nanogels in order to enhance controlled drug loading and a sustained release. © 2016 Bentham Science Publishers.

Goikuria U.,University of the Basque Country | Larranaga A.,University of the Basque Country | Vilas J.L.,University of the Basque Country | Vilas J.L.,Basque Center for Materials | Lizundia E.,University of the Basque Country
Carbohydrate Polymers | Year: 2017

Due to the potential of CNC-based flexible materials for novel industrial applications, the aim of this work is to improve the thermal stability of cellulose nanocrystals (CNC) films through a straightforward and scalable method. Based of nanocomposite approach, five different metallic nanoparticles (ZnO, SiO2, TiO2, Al2O3 and Fe2O3) have been co-assembled in water with CNCs to obtain free-standing nanocomposite films. Thermogravimetric analysis (TGA) reveals an increased thermal stability upon nanoparticle. This increase in the thermal stability reaches a maximum of 75 °C for the nanocomposites having 10 wt% of Fe2O3 and ZnO. The activation energies of thermodegradation process (Ea) determined according to Kissinger and Ozawa-Flynn-Wall methods further confirm the delayed degradation of CNC nanocomposites upon heating. Finally, the changes induced in the crystalline structure during thermodegradation were followed by wide angle X-ray diffraction (WAXD). It is also observed that thermal degradation proceeds at higher temperatures for nanocomposites having metallic nanoparticles. Overall, experimental findings here showed make nanocomposite approach a simple low-cost environmentally-friendly strategy to overcome the relatively poor thermal stability of CNCs when extracted via sulfuric acid assisted hydrolysis of cellulose. © 2017 Elsevier Ltd

Zong Y.,University of Wollongong | Zheng T.,University of Wollongong | Martins P.,University of Minho | Lanceros-Mendez S.,University of Minho | And 4 more authors.
Nature Communications | Year: 2017

Since the first magnetoelectric polymer composites were fabricated more than a decade ago, there has been a reluctance to use piezoelectric polymers other than poly(vinylidene fluoride) and its copolymers due to their well-defined piezoelectric mechanism and high piezoelectric coefficients that lead to superior magnetoelectric coefficients of >1 V cm-1 Oe-1. This is the current situation despite the potential for other piezoelectric polymers, such as natural biopolymers, to bring unique, added-value properties and functions to magnetoelectric composite devices. Here we demonstrate a cellulose-based magnetoelectric laminate composite that produces considerable magnetoelectric coefficients of ≈1.5 V cm-1 Oe-1, comprising a Fano resonance that is ubiquitous in the field of physics, such as photonics, though never experimentally observed in magnetoelectric composites. The work successfully demonstrates the concept of exploring new advances in using biopolymers in magnetoelectric composites, particularly cellulose, which is increasingly employed as a renewable, low-cost, easily processable and degradable material. © The Author(s) 2017.

Garcia-Huete N.,Basque Center for Materials | Laza J.M.,University of the Basque Country | Cuevas J.M.,Gaiker Technology Center | Vilas J.L.,Basque Center for Materials | And 2 more authors.
Radiation Physics and Chemistry | Year: 2014

A gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical, chemical and mechanical properties. Gamma irradiation originates free radicals able to induce chain scission or recombination of radicals, which induces annihilation, branching or crosslinking processes. The aim of this work is to research the structural, thermal and mechanical changes induced on a commercial polycyclooctene (PCO) when it is irradiated with a gamma source of 60Co at different doses (25-200kGy). After gamma irradiation, gel content was determined by Soxhlet extraction in cyclohexane. Furthermore, thermal properties were evaluated before and after Soxhlet extraction by means of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), as well as mechanical properties were measured by Dynamic Mechanical Thermal Analysis (DMTA). The results showed the variations of the properties depending on the irradiation dose. Finally, a first approach to evaluate qualitatively the shape memory behaviour of all irradiated PCO samples was performed by a visually monitoring shape recovery process. © 2014 Elsevier Ltd.

Iturrospe A.,University of the Basque Country | San Felices L.,University of the Basque Country | Reinoso S.,University of the Basque Country | Artetxe B.,University of the Basque Country | And 4 more authors.
Crystal Growth and Design | Year: 2014

Hydrothermal reaction of the Keggin-type [-GeW11O 39]8- anion with copper(II) complexes of the tetradentate N-donor ligands N,N′-dimethyl-N,N′-bis-(pyridine-2-ylmethyl)-1,2- diaminoethane (bpmen) or N,N′-dimethyl-N,N′-bis-(pyridine-2- ylmethyl)-1,3-diaminopropane (bpmpn) results in three new hybrid compounds [Cu(bpmen)(H2O)][GeW12O40{Cu(bpmen)}]·3. 5H2O (1), [GeW12O40{Cu(bpmpn)(H 2O)}2]·3H2O (2), and [Cu(bpmpn)(H 2O)][GeW12O40{Cu(bpmpn)}]·8H 2O (3). All compounds have been characterized by elemental analyses and infrared spectroscopy, and their structures have been established by single-crystal X-ray diffraction. Both 1 and 3 contain monodecorated polyanions and additional complex cations, but their layered structures show noticeable differences. For 1, the polyanions are arranged in rows whose stacking generates intralamellar cavities where complex cations and lattice water molecules are hosted, whereas double-layers of hybrid anions pillared by the cations occupying the interlamellar space are observed for 3. In the case of 2, the packing of trans-didecorated clusters generates honeycomb-like metalorganic layers and perpendicular hexagonal channels where Keggin moieties are nested. A combination of thermogravimetric and variable temperature powder X-ray diffraction analyses show that dehydration of 1 and 2 results in thermally stable, crystalline phases. Dehydrations are fully reversible upon exposure to air and proceed via single-crystal to single-crystal transformations implying rupture/formation processes in the copper(II) bonding and consequent geometrical and conformational modifications in the complexes. Transformations have been followed by single-crystal X-ray diffraction, allowing for the structures of the anhydrous phases [GeW12O40{Cu(bpmen)}2] (1a) and [GeW12O40{Cu(bpmpn)}2] (2a) to be determined. Dehydration of 1 into 1a with consequent formation of neutral, didecorated clusters does not result in the collapse of the intralamellar cavities but rather in an open-framework structure with slit-shaped micropores. Structural variations between 1 and 2 and their corresponding anhydrous phases are reflected in the electron paramagnetic resonance spectra. © 2014 American Chemical Society.

Legarra E.,Basque Center for Materials | Apinaniz E.,University of the Basque Country | Plazaola F.,University of the Basque Country
Intermetallics | Year: 2016

The influence of the different crystal structures and the variation of the lattice parameter on the evolution of the magnetism in the order-disorder transition produced by crushing and mechanical milling in the intermetallic Fe75Al25-xSix alloys (x = 7.5, 12.5, 17.5, 25) has been systematically studied by means of XRD measurements, Mössbauer spectroscopy and magnetic measurements. The results indicate that with the addition of Si to binary Fe75Al25 alloy the mechanical deformation needed to disorder the alloys increases. At the same time the variation of the lattice parameter due to the disorder is reduced as Si is added. The magnetic measurements indicate that there is a complex behaviour in ternary alloys with an opposite influence of Si and Al during the order-disorder transition. However, when the transition is fulfilled there is a linear relationship between structural and magnetic parameters. © 2015 Elsevier Ltd.

Lizundia E.,University of the Basque Country | Vilas J.L.,Basque Center for Materials | Leon L.M.,University of the Basque Country | Leon L.M.,Basque Center for Materials
Carbohydrate Polymers | Year: 2015

In this work, crystallization, structural relaxation and thermal degradation kinetics of neat Poly(l-lactide) (PLLA) and its nanocomposites with cellulose nanocrystals (CNC) and CNC-grafted-PLLA (CNC-g-PLLA) have been studied. Although crystallinity degree of nanocomposites remains similar to that of neat homopolymer, results reveal an increase on the crystallization rate by 1.7-5 times boosted by CNC, which act as nucleating agents during the crystallization process. In addition, structural relaxation kinetics of PLLA chains has been drastically reduced by 53% and 27% with the addition of neat and grafted CNC, respectively. The thermal degradation activation energy (E) has been determined from thermogravimetric analysis in the light of Kissinger's and Ozawa-Flynn-Wall theoretical models. Results reveal a reduction on the thermal stability when in presence of CNC-g-PLLA, while raw CNC slightly increases the thermal stability of PLLA. Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy results confirm that the presence of residual catalyst in CNC-g-PLLA plays a pivotal role in the thermal degradation behavior of nanocomposites. © 2015 Elsevier Ltd. All rights reserved.

Legarra E.,Basque Center for Materials | Apinaniz E.,University of the Basque Country | Plazaola F.,University of the Basque Country
Journal of Alloys and Compounds | Year: 2016

The aim of this work is to study the influence of the coexistence of different ordered structures on the evolution of the magnetism in the order-disorder transition produced by crushing and mechanical milling in the intermetallic Fe70Al30-xSix alloys. First, XRD measurements show that the three ordered samples have both D03 and B2 structures simultaneously and that the disordering process takes place in two stages. In the first one the D03 structure starts to disorder and in the second one, once the D03 structure has almost disappeared, the B2 starts to disorder. Second, Mössbauer spectroscopy and magnetic measurements show that there is an enhancement of the magnetic properties related to the structure change and to the increase of the lattice parameter in the order-disorder transition. The change of the magnetic behaviour is linked to the disordering of B2 structure in these alloys. © 2016 Elsevier B.V.

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