In recent years with respect to the advances in technology and science, the need for new materials with special properties is more than ever. In this regard, polymer nanocomposites, due to their lightweight, low cost, recyclability, high mechanical properties, and compatibility with the environment, are facing great demands in various industries compared with metallic compounds and ceramics. One of the main shortcomings of polymers is that most of them cannot be used alone and should be modified. The main methods for modification of polymers include blending, grafting, and coating [1–7]. Blending is the most preferred method due to relative ease of process and cost-effectiveness, and can also enhance the properties of polymer materials. Blending has also three methods which include melt blending, solution blending, and in situ polymerization blending [1–3, 8]. In order to blend polymers with each other, they should be compatible and the microstructure of the resulting blend is determined by the blending method and polymer matrices.
Fluoropolymers are one of the best protective materials and they are often used as protective films or coatings . PVDF is a fluoropolymer with good thermal stability, mechanical properties, resistance to chemical substances, oxidation, and UV irradiation as well as a fantastic appearance. PVDF is also one of the few semi-crystalline polymers having three crystalline phases α, β, and γ phases . The main disadvantage of PVDF is its high price, thus it is often mixed with other polymers to solve this problem [6, 7, 9]. One of the polymers that has good compatibility with PVDF and can be blended with it is poly(methyl methacrylate) (PMMA). PMMA can effectively lower the cost and also improve the adhesion properties of PVDF and is often chosen to blend with it [10, 11]. PMMA is an amorphous polymer and has high rigidity, transparency, and chemical resistance which is widely used in various applications . The miscibility and compatibility of PVDF and PMMA have been extensively studied in many studies. These two polymers have proved to be compatible in a wide range of compositions in solid state and they are completely miscible in the molten state [13–15]. The main reason for this miscibility is the intermolecular interactions between carbonyl groups of PMMA and the CH2 and CF2 groups of PMMA. These interactions include dipolar interactions and hydrogen bondings, respectively. Studies also showed that the blending of PVDF with PMMA results in a transfer in crystallization from α phase to β phase which is thermodynamically unstable in the pure form of PVDF [7, 16, 17]. Another method to improve the properties of polymers is to add fillers to their matrix, hence, there is much interest in the investigation of various combinations of polymers and fillers [18, 19]. It has been reported that by the addition of small amounts of nanohybrids to polymer matrices a significant improvement in their physical properties was observed. Carbon nanotubes (CNT) and nanoclays which are one and two-dimensional fillers are widely studied in recent years [1–3]. In addition, graphene and its derivatives (e.g. graphene oxide (GO) and reduced graphene oxide (rGO)) have attracted much interest in recent years due to their exceptional properties, and the incorporation of these fillers in the polymer matrices has led to significant improvements [4, 9]. Reduced graphene oxide is the oxidized form of graphene with relatively lower functional groups in comparison with GO which can solve the dispersion problem of graphene sheets. As a result of the existence of carbonyl, carboxyl, and hydroxyl groups on its surface, rGO can be dispersed in polar solvents and also facilitate the formation of interactions with the matrices possessing the same functional groups through strong hydrogen bonds . As a result of the extraordinary mechanical, thermal, and optical properties of rGO alongside its ease of dispersion in many solvents and matrices which is due to the presence of oxygen-containing functional groups, it has been used as a reinforcing filler to enhance different properties of PVDF, PMMA, and PVDF/PMMA blends [21–23]. Although rGO is an electrical conductor, because of the availability of oxygen-containing groups on its surface its conductivity properties can be further enhanced to be used for electrical applications. In order to increase the conductivity of different materials, one-dimensional metals such as Ag, Cu, and Au can be good choices [24–26]. By the incorporation of these metals which have unique properties into polymer matrices, new composites with desirable properties can be produced. One of the best metal particles for enhancing the electrical properties of rGO is silver nanoparticles and the resulting product is known as rGO-Ag nanohybrid. These nanohybrids have been used in many studies to add electrical conductivity, mechanical enhancement, thermal stability, and also antibacterial and antifouling properties [22, 27, 28].
In this study, rGO-Ag nanohybrids were synthesized by the reduction of silver ions on the rGO surface using ascorbic acid as a reducing agent. Synthesis was carried out in an aqueous solution, which is a versatile, low-cost, and environmentally friendly process. These nanohybrids could be easily dispersed into water or common organic solvents to form a stable suspension without any additional protection by polymeric or surfactant stabilizers. Since rGO-Ag nanohybrids possess very good electrical, mechanical, and thermal properties, they can be used to enhance the properties of PVDF/PMMA blends. Thus, the main goal of this study is to prepare a PVDF/PMMA nanocomposite containing silver nanoparticles decorated rGO nanosheets and an investigation of its properties which was not carried out in past studies.