Computational Studies of PVDF and P(VDF-TrFE) Nanofilms Polarization During Phase Transition Revealed by Emission Spectroscopy
Bystrov V.S., Paramonova E.V., Dekhtyar Y., Katashev A., Polyaka N., Bystrova A.V., Sapronova A.V., Fridkin V.M., Kliem H., Kholkin A.L.
Institute of Mathematical Problems of Biology RAS, Pushchino, Russia
Depart.Cer. Glass Eng. & CICECO, University of Aveiro, Averio, Portugal
Institute of Biomed. Eng. Nanotechnology, Riga Technical University, Riga, Latvia
Institute of Theoretical and Experimental Biophysics RAS, Pushchino, Russia
Bergen Center for Computational Science, Unifob AS, Bergen, Norway
Institute of Crystallography, RAS, Moscow, Russia
Institute of Electr.Eng.Phys., University of Saarland, Saarbruecken, Germany
Abstract. Electronic structure and self-polarization of P(VDF-TrFE) Langmuir-Blodgett nanofilms according to their thickness, composition and structural conformation under temperature phase transition were analyzed. Both thermo-stimulated exoelectron emission (TSEE) spectroscopy and computational simulation, including quantum-chemical calculations from first principles, were provided. PVDF and composite P(VDF-TrFE) (70:30) molecular chains as Trans and Gauche conformers as well as crystal cells were modeled for these agreed-upon TSEE analyses. The quantum-chemical calculations and the computational simulation were based on the density functional theory (DFT) as well as semi-empirical (PM3) methods. It was demonstrated that the energies of electron states as well as the total energies of the studied PVDF and P(VDFTrFE) molecular clusters during phase transformation influenced electron work function and electron affinity. The performed combined analysis of the TSEE experimental data as well as the computational data of the molecular models showed the effectiveness of that joined approach. TSEE for the first time was in use for contactless measurements of nanofilm polarization and characterizations of the phase transition. The proposed new method can be widely used in nanobiomedicine, particularly in development of new bone bio-implants, including built-in sensors (new smart nanotechnology).
Key words: polymer ferroelectrics, polarization and depolarization, thermo-stimulated exoelectron emission, computational molecular modeling, density functional theory, semi-empirical method, electron band energies, electron work function and affinity.
