LiBr₂ and MnCl₂ mixed fillers effects on the optical, structural and electron spin resonance properties of polyvinylidene fluoride films

Polymers have attracted the attention of scientific and technological researchers because of their wide applications. Polyvinylidene fluoride (PVDF) is a polycrystalline polymer started drawing scientific interest in the seventies, because of its extraordinary pyroend piezoelectric properties. These properties combined with both high elasticity and processing ability lend this material numerous technological applications ^[1]. Recently, PVDF is widely used in biotechnology ^[2], photo-recording ^[3], microwave modulation ^[4] and in rechargeable lithium batteries ^[5]. Filling PVDF enhances its electromagnetic wave sensing feature due to its increased magnetic activity ^[6].

Another feature that distinguishes PVDF from other polymers is its polymorphism, that is, it may present at least four crystalline phases, namely a, ß, d and ? ^[7]. Moreover, an increasing interest has been devoted to PVDF as electric and/or magnetic field sensors. For this application, PVDF was filled with transition metal halides ^[8]. Fillers are used in polymers for a variety of reasons: cost reduction, improved processing, density control, optical effect, thermal conductivity, control of thermal expansion, electrical properties, magnetic properties, flame retardancy and hardness, and tear resistance ^[9]. For example, in optical, electrical and magnetic applications, fillers such as LiBr₂ and MnCl₂ are used to provide better optical, electrical and magnetic properties. Manganese is well known as a magneto-active multivalent element; thus its halides can be used as fillers to modify the electric conduction, the optical absorption and magnetic properties of PVDF.

On the other hand, MnCl₂ is considered as a good candidate for one or two dimensional phenomena ^[10] and for optical memory device ^[11]. Spectroscopic and physical properties of metal halide doped polymers are extensively studied. But research on a mixture of LiBr₂ and MnCl₂-containing PVDF limited, to our knowledge. Therefore, the present study is devoted to shed some light on the role of filling PVDF with a mixture of LiBr₂ and MnCl₂ on optical, structural and electron spin resonance properties.