Suchergebnisse

Herein, we elucidate the impact of tubular confinement on the structure and relaxation behavior of poly(vinylidene difluoride) (PVDF) and how these affect the para-/ferroelectric behavior of this polymer. We use PVDF nanotubes that were solidified in anodic aluminum oxide (AAO) templates. Dielectric spectroscopy measurements evidence a bimodal relaxation process for PVDF nanotubes: besides the bulk-like α-relaxation, we detect a notably slower relaxation that is associated with the PVDF regions of restricted dynamics at the interface with the AAO pore. Strikingly, both the bulk-like and the interfacial relaxation tend to become temperature independent as the temperature increases, a behavior that has been observed before in inorganic relaxor ferroelectrics. In line with this, we observe that the real part of the dielectric permittivity of the PVDF nanotubes exhibits a broad maximum when plotted against the temperature, which is, again, a typical feature of relaxor ferroelectrics. As such, we propose that, in nanotubular PVDF, ferroelectric-like nanodomains are formed in the amorphous phase regions adjacent to the AAO interface. These ferroelectric nanodomains may result from an anisotropic chain conformation and a preferred orientation of local dipoles due to selective H-bond formation between the PVDF macromolecues and the AAO walls. Such relaxor-ferroelectric-like behavior has not been observed for nonirradiated PVDF homopolymer; our findings thus may enable in the future alternative applications for this bulk commodity plastic, e.g., for the production of electrocaloric devices for solid-state refrigeration which benefit from a relaxor-ferroelectric-like response. ; J.M. acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant, agreement No. 654682. A.A. and A.I. acknowledge financial support from the Spanish Ministry Ministerio de Economia y Competitividad (MINECO) (code: MAT2015-63704-P (MINECO/FEDER, UE)) and the Eusko Jaurlaritza (Basque Government) (code: IT-654-13). A.C. would like to acknowledge the financial support of the EPSRC (EP/M014142/1). A.N., T.A.E., and C.M. acknowledge financial support from MINECO (codes: MAT2014-59187-R, MAT2015-66443-C02-1-R, and MAT2014-53437-C2-1P, respectively). N.S. is in addition grateful for support from a European Research Council ERC Starting Independent Research Fellowship under the grant agreement No. 279587. ; Peer Reviewed

10 pags., 7 figs., 2 tabs. ; In this work, we prepare and characterize multiphasic thin films containing poly(ε-caprolactone), PCL, poly(butylene succinate), PBS, and a poly (butylene succinate-ran-ϵ-caprolactone) (PBS-ran-PCL) random copolyester. To that aim, thin films were prepared by sequential dipping of a silicon substrate into chloroform solutions of the respective polymers. The preparation method resulted in films with varying compositions of PCL and PBS components depending on the initial concentration of the dipping solutions and the number of dipping steps employed for the preparation of the samples. Atomic force microscopy (AFM), grazing incidence X-ray scattering at wide angle (GIWAXS) and scattering-type scanning near-field optical microscopy (s-SNOM) and Fourier transform infrared nanospectroscopy (nano-FTIR) were employed to characterize the films obtained. As chloroform can dissolve all components, the final composition of the film was always rich in the last deposited layer component. The thin films obtained were semicrystalline with a complex axialitic or dendritic morphology of the dominant component (that one deposited last) with traces of the other components, whose presence and location was revealed by s-SNOM/nano-FTIR. ; This study was supported by Spanish Ministry of Science, Innovation and Universities (MAT2017- 83014-C2-1-P, MAT2017-83014-C2-2-P, PID2019-107514 GB-I00/AEI/ 10.13039/501100011033 and PID2019-106125 GB-I00/AEI/ 10.13039/501100011033). We also acknowledge funding by Basque Government through grant IT1309-19. The authors acknowledge beamtime access at ALBA BL11 via proposal 2018072905 and the assistance of JC Martinez during the measurements. We would also like to thank the financial support provided by the BIODEST project; this project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 778092. CO wants to acknowledge "Diputaci on Foral de Gipuzkoa" in the framework program "Fellows Gipuzkoa de Atracci ́on y Retenci ́on de Talento". RH is member of the Interdisci-plinary Platform for Sustainable Plastics towards a Circular Economy (SusPlast) from the Spanish National Research Council (CSIC).

In this work we present the formation of laser induced periodic surface structures (LIPSS) on spin-coated thin films of several model aromatic polymers including poly(ethylene terephthalate), poly(trimethylene terephthalate) and poly carbonate bis-phenol A upon irradiation with femtosecond pulses of 795 and 265 nm at fluences well below the ablation threshold. LIPSS are formed with period lengths similar to the laser wavelength and parallel to the direction of the laser polarization vector. Formation of LIPSS upon IR irradiation at 795 nm, a wavelength at which the polymers absorb weakly, contrasts with the absence of LIPSS in this spectral range upon irradiation with nanosecond pulses. Real and reciprocal space characterization of LIPSS obtained by Atomic Force Microscopy (AFM) and Grazing Incidence Small Angle X-ray Scattering (GISAXS), respectively, yields well correlated morphological information. Comparison of experimental and simulated GISAXS patterns suggests that LIPSS can be suitably described considering a quasi-one-dimensional paracrystalline lattice and that irradiation parameters have an influence on the order of such a lattice. Fluorescence measurements, after laser irradiation, provide indirect information about dynamics and structure of the polymer at the molecular level. Our results indicate that the LIPSS are formed by interference of the incident and surface scattered waves. As a result of this process, heating of the polymer surface above its glass transition temperature takes place enabling LIPSS formation. © 2013 the Owner Societies. ; Funding from MICINN, Spain (Projects CTQ2010-15680,FIS2009-09522, MAT2012-33517 and CSD2007-00013) and Junta de Castilla y León (Project SA086A12-2). The experiments performed at BW4 in HASYLAB (DESY,Germany) were supported by the European Union (Contract RII3-CT-2004-506008 (IA-SFS).MINECO (previous MICINN), Spain, Ramón y Cajal contract (RYC-2011-08069), FPI fellowship and PTA contract ; Peer Reviewed