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.Graphical abstract
Highlights
This report presents results of broadband dielectric spectroscopy studies in the composite system for which a strong interaction between the polymer matrix host and barium strontium titanate (BST) ferroelectric micro-particles can be expected
Results presented above show the unusual impact of the addition of BST micro particles on the polyvinylidene difluoride (PVDF) polymer
All these indicate the ‘feedback’ interaction between PVDF polymer and BST particles: it very strongly manifests for τ (T ) evolution, but it is notable for ε (T ) behavior
Summary
This report presents results of broadband dielectric spectroscopy studies in the composite system for which a strong interaction between the polymer matrix host (polyvinylidene fluoride, PVDF) and barium strontium titanate (BST) ferroelectric micro-particles can be expected. It is shown that the addition of BST particles qualitatively changes dynamics, converting the SA-type dynamics in PVDF to Arrhenius one in BST/PVDF composites The latter crossovers to the relaxor-type SA dynamics on cooling exactly at the glass temperature of PVDF. Studies focused on dynamics are accomplished by the analysis of the ferroelectric-paraelectric transition in PVDF (Tc = 453−473 K) and a polymer-solid particles composite. They led to the finding of the strong pretransitional anomaly of dε/dT , extending even to the vicinity of the room temperature, and the suggestion of the semi-discontinuous nature of melting in PVDF and its composites. We stress the importance of the insight into fundamental properties of PVDF and its composites, due to the enormous and developing range of applications
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