Polyvinylidene difluoride-based composite: glassy dynamics and pretransitional behaviour

Abstract

This paper presents results of broadband dielectric spectroscopy studies in the composite system for which particularly strong interactions between polyvinylidene difluoride (PVDF: ferroelectric polymer, TC = 453−473 K) matrix and barium strontium titanate (BST) ferroelectric micro-particles can be expected. For PVDF the super-Arrhenius (SA) dynamics, associated with segmental motions freezing at the glass temperature Tg = 235 K, is evidenced. The addition of BST particles qualitatively changes dynamics, converting the SA-type behaviour in PVDF to the clear Arrhenius one in BST/PVDF composite. The latter crossovers to the relaxor-type SA dynamics on cooling, exactly at the glass temperature of PVDF. The preliminary model explaining such unique behaviour is proposed. For the consistent portraying of the SA evolution of primary relaxation times in PVDF and BST/PVDF, the activation energy index analysis was carried out and the new equation, entropy and symmetry controlled, is introduced. Studies are accomplished by the analysis of the ferroelectric-paraelectric transition in PVDF and for the composite system. They led to the discovery of the strong pretransitional anomaly of dε/dT , extending even to the vicinity of the room temperature, The semi-discontinuous nature of melting in PVDF and its composites, with the discontinuity metric T ≈ 20 K is suggested.

Polymer matrix ferroelectric composites under pressure: Negative electric capacitance and glassy dynamics

“…Barium strontium titanate belongs to the group of classical ferroelectric solids with the perovskite crystalline structure [16][17][18]. The applied in studies presented below BST powder had grains with an average diameter d = 0.7 μm and a Curie temperature T C = 286 K [19]. BST is broadly applied in modern electronic, particularly within integrated circuits.…”

“…fraction of BST) the dynamics between T m and T g is clearly Arrhenius (A) type, with a constant activation energy. On cooling below T g , a new SA relaxation process associated with the relaxor glassy nature of BST appears [19,20]. Notable is the coincidence of T g in PVDF and the A → SA crossover temperature in the BST/PVDF composite [19].…”

“…On cooling below T g , a new SA relaxation process associated with the relaxor glassy nature of BST appears [19,20]. Notable is the coincidence of T g in PVDF and the A → SA crossover temperature in the BST/PVDF composite [19].…”

New paradigm for configurational entropy in glass-forming systems

“…Eq. ( 13) has already been used for describing dynamics in glass-forming polyvinylidene difluoride (PVDF), PVDF + Barium-Strontium-Titanate (BST) microparticles composite, 58 and in its parallel form for describing relaxation time in relaxor ceramics. 59 Nevertheless, these tests cannot be considered as a crucial validation of Eq.…”

Universal behavior of the apparent fragility in ultraslow glass forming systems

“…basing on high resolution and 'high density' (the number of tested temperatures per decade) experimental broad band dielectric spectroscopy studies. They were carried out in a broad range of temperatures for selected glass formers ranging from low molecular weight liquids (glycerol) [36], polymers (polystyrene, polyvinyludene disulfide -PVDF) [39], resin (EPON 828: diglycidyl ether of bisphenol-A) [40], liquid crystals (5CB:…”