Computational modelling of the effect of surfaces on polyvinyldenedifluoride

  • Francesco Pelizza

Student thesis: Doctoral Thesis

Abstract

The physical properties of polyvinyldenediluoride (PVDF) polymorphs and the effect of surfaces on PVDF properties have been investigated with computational modelling to address crystallinity issues that such semi-crystalline polymer presents. Indeed, PVDF has the potential to support new technology generation of lexible electronic devices, but to preparere liable devices made with PVDF, such polymer needs to be sampled at high crystalline grade.As PVDF is a semi-crystalline polymer its intrinsic lexibility represents a major advantage for lexible electronics which also increases manufacturing complexity of such material. To understand the crystalline behaviour of PVDF it is necessary to computationally investigate its fundamental physical properties per each of its crystal phase and the main behaviour of PVDF in conditions of inite temperature.Density functional theory (DFT) calculations has been used as a quantum mechanical (QM) tool to solve the electronic structures of PVDF polymorphs obtaining structural information such as geometries, energetics, spontaneous polarisation and vibrational frequencies. Furthermore the impact of including van derWaals (vdW) forces in DFT was evaluated showing that the vdW-DF DFT functional had the best physical properties prediction agreement with experimental observations.The vibrational frequencies of all PVDF polymorphs were computationally determined to verify the metastability of every crystal phase determined in the present study. Furthermore, the vibrational frequencies determination allowed to enrich the knowledge about adsorption peaks that each PVDF structure possesses to ease the computation to experimental IR spectra comparison.The optimised geometries of PVDF crystals obtained from the DFT investigation have been scaled to molecular dynamics (MD) since it represents a time consistent methodology to follow the evolution of molecular interactions between particles. The interest was to compute the inite temperature dynamics, ensuring the use of the best performing force field and to gather new knowledge about the crystalline phase formation of PVDF liquid melts under different conditions such as bulk and confined between surface layers.The effect of polymer confinement and surface/polymer electrostatics interaction were evaluated in such study showing that electrostatics played a main role in driving the formation of highly crystalline PVDF systems.
Date of Award1 Oct 2017
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorKaren Johnston (Supervisor) & Leo Lue (Supervisor)

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