Bio-nanocomposite hydrogels based on sodium alginate (SA) as polymer matrix and graphene oxide (GO) nanosheets with zinc as crosslinking agent were synthesized with the aim of incorporating the ...intrinsic properties of their constituents (bioactivity and antimicrobial activity). Thus, stable and highly interconnected networks were obtained from GO nanosheets dispersed in SA matrices through interactions with low amounts of zinc. The GO nanosheets were successfully incorporated into the alginate matrix in the form of a complex nano-network involving different interactions: Bonds between alginate chains induced by Zn ions (egg box structure), interactions between GO nanosheets through Zn ions and hydrogen bonds between alginate chains, and GO nanosheets. The molecular interactions and morphology were confirmed by Fourier-transform infrared spectroscopy and transmission electron microscopy. The composite's structural organization showed enhanced thermal stability. The glass transition temperature shifted to a higher temperature due to the reduced mobility induced by additional crosslinking bonds after incorporating the GO nanosheets and Zn into the polymer matrix. Finally, the dielectric behavior revealed that charge carrier mobility was hampered by the compact structure of the nanonetwork, which reduced conductivity. The combined properties of these nanocomposite hydrogels make them attractive biomaterials in the field of regenerative medicine and wound care since both surface bioactivity and antibacterial behavior are two critical factors involved in the success of a biomaterial.
Poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) networks were prepared from macromonomer diols functionalized with methacrylic anhydride, which allows one to get self-crosslinkable polymers. ...Besides, both macromonomers were copolymerized to get copolymer networks with different compositions (namely, PCL/PLA: 0/100, 70/30, 50/50, 30/70, 100/0). Dielectric and calorimetric experiments allow one to conclude the microphase separation of the system: one phase made of pure PCL domains while the second one consists of caprolactone units, which somehow plasticize PLA and moves its main relaxation (glass transition) to lower temperatures. The effect of crosslinking PLA on the dynamics of the system was further investigated by comparing with the dynamics for linear PLA.
Poly(L-lactide) networks (PmLA) hydrophilized with different amounts of 2-hydroxyethyl acrylate (HEA) were investigated by dielectric relaxation spectroscopy, thermally stimulated depolarization ...currents, and differential scanning calorimetry. The incorporation of HEA units in the PmLA network, with the aim of modulating the water sorption capacity of the system, results in a material with a complex behavior. The system consists of phase-separated microdomains richer in one or the other comonomers that constitute the network. Initially, the addition of smalls amount of HEA units in the network gives rise to a one-phase, two-component system; however, when the amount of HEA in the system increases, a new phase (HEA-rich one) is formed containing some mLA chains that modify the main relaxation mode of these domains and the local dynamics of the system. The structure of the system has been analyzed by comparing the relaxational modes in the PmLA and PHEA homonetworks with those in the copolymer networks.
In order to tailor dielectric response and electrical conductivity, novel polymer blends based on poly(vinylidene fluoride (PVDF) and different fillers composed by ...poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and PEDOT:PSS/ionic liquids (ILs): PEDOT:PSS/N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (C2mpyrFSI) and PEDOT:PSS/N-ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (C2mpyrTFSI), with different PEDOT:PSS/IL contents (10, 20 and 40 wt%) were prepared through solvent casting. The morphological, physical-chemical and thermal properties of the polymer blends were evaluated, together with the influence of PEDOT:PSS/IL on the PVDF crystallization kinetics, dielectric and electrical conductivity.
The incorporation of PEDOT:PSS/IL in the polymer matrix lead to a decrease of the PVDF spherulites. Furthermore, it was detected that both PEDOT:PSS and IL act as nucleation agents, promoting the homogeneous crystallization of PVDF as well as the crystallization into its b and g polar phases. The electrical conductivity formalism revealed significant contributions of PEDOT:PSS/IL to the electrical conductivity behavior of the blends, being thermally activated and described by the charge transport mechanism. Further, the dc conductivity increases due to the higher number of charge carriers of the PEDOT:PSS/IL content.
The tailorable electrical characteristics of the PVDF/PEDOT:PSS-IL blends demonstrate their potential for applications in areas such as ionic actuators and battery devices.
Display omitted
•The polymer phase and the electrical conductivity of PVDF/PEDOT:PSS/IL blends are studied.•The inclusion of PEDOT and IL acts as a nucleation agent for PVDF homogeneous crystallization.•The interaction between PVDF and PEDOT:PSS/IL promotes PVDF crystallization into its polar β and γ phases.•The PEDOT:PSS/IL content leads to an increase of the dc electrical conductivity, the electrical percolation being between 20 wt% and 40 wt%.•The dc electrical conductivity is thermally activated and described by the charge transport mechanism.
Display omitted
•Permeability and diffusion coefficient of N2, O2 and CO2 has been determined in two polymers.•Two poly(α-alkyl β,L-aspartate)s (PAALA-n) were studied.•One of these membranes was ...crystalline (PAALA-1) and the other one was amorphous (PAALA-6).•Diffusion coefficient and permeability measurements were carried out using the time-lag techniques.•From activation free energy and the activation entropy the configurational entropy is determinate.
The permeability and diffusion coefficient of gases such as N2, O2 and CO2 through two polymeric membranes of poly(α-alkyl β,L-aspartate)s (PAALA-n) were determined by the “time-lag” method. One of these membranes was crystalline (PAALA-1) and the other one was amorphous (PAALA-6). The comparison of the obtained result for both membranes is addressed by the calculation of the so called configurational entropy. The study has been done in the range of temperatures 20°C to 70°C.
En esta tesis se han estudiado las propiedades difusivas de tres filmes de polietileno lineal de baja densidad a los gases nitrógeno, oxígeno y dióxido de carbono. Se ha medido los coeficientes de ...permeabilidad, difusión y solubilidad aparentes en función de la temperatura, la presión y el tiempo de templado. La evolución de los resultados con el cambio de presión ha sido interpretada utilizando el modelo dual de sorción, así mismo, la evolución con la temperatura ha sido interpretada en términos del modelo de volumen libre desarrollado por Fujita y modificado por nosotros para polímeros semicristalinos. Finalmente se ha llevado a cabo un estudio de la permselectividad de estos filmes los citados gases también en función de la temperatura, presión y tiempo de templado.
In this study, we determined the pH of different saline and multipurpose contact lens solutions available on the Spanish market. We examined 10 samples of 14 solutions, seven of which are saline ...solutions and seven multipurpose ones, from different manufacturers. Both types of solution were found to have significant variations in pH, with values ranging from 6.70 to 7.57 for the saline solutions and 6.84 to 7.63 for the multipurpose solutions. We concluded that the solutions should not affect the ocular physiological performance because their pH values are within the buffering capacity of the eye.
PDF
