Vibrational properties of ferroelectric<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>-vinylidene fluoride polymers and oligomers

Abstract

We utilize a plane-wave density-functional theory approach to investigate the vibrational properties of the all-trans ferroelectric phase of poly(vinylidene fluoride) $(\ensuremath{\beta}\text{-PVDF})$ showing that its stable state corresponds to the $Ama2$ structure with ordered dihedral tilting of the VDF monomers along the polymer chains. We then combine our theoretical analysis with IR spectroscopy to examine vibrations in oligomer crystals that are structurally related to the $\ensuremath{\beta}\text{-PVDF}$ phase. We demonstrate that these materials---which can be grown in a highly crystalline form---exhibit IR activity similar to that of $\ensuremath{\beta}\text{-PVDF}$, making them an attractive choice for the studies of electroactive phenomena and phase transitions in polymer ferroelectrics.