New Materials Based on Polyvinylpyrrolidone-Containing Copolymers with Ferromagnetic Fillers

Abstract

The article investigates the peculiarities of the effect of ferromagnetic fillers (FMFs) of various natures (Ni, Co, Fe, FeCo, SmCo5) on the formation of the structure and properties of 2-hydroxyethylmethacrylate (HEMA) with polyvinylpyrrolidone (PVP) copolymers. The composites were characterized using FTIR-spectroscopy, SEM, DMTA, magnetometry of vibrating samples, specific electrical resistivity studies, and mechanical and thermophysical studies. The formation of a grafted spatially crosslinked copolymer (pHEMA-gr-PVP) was confirmed and it was established that the FMF introduction of only 10 wt.% into the copolymer formulation increased the degree of crosslinking of the polymer network by three times. The surface hardness of composites increased by 20–25%. However, the water content decreased by 16–18% and lay within 42–43 wt.%, which is a relatively high number. The heat resistance of dry composites was characterized by Vicat softening temperature, which was 39–42 °C higher compared to the unfilled material. It was established that the obtained composites were characterized by a coercive force of 200 kA × m−1 and induction of a magnetic field at the poles of 4–5 mT and 10–15 mT, respectively. The introduction of FMF particles into pHEMA-gr-PVP copolymers, which, in the dry state, are dielectrics, provides them with electrical conductivity, which was evaluated by the specific volume resistance. Depending on the FMF nature and content, as well as their orientation in the magnetic field, the resistance of filled materials could be regulated within 102–106 Ohm·m. Therefore, the modification of HEMA with PVP copolymers by ferromagnetic fillers of various natures provides the possibility of obtaining materials with unique predicted properties and expands the fields of their use, for instance as magnetic sorbents for various applications, as well as the possibilities associated with their being electrically conductive materials that can respond by changing of electrical conductivity, depending on various factors.

Metal-Filled Polyvinylpyrrolidone Copolymers: Promising Platforms for Creating Sensors

“…Previous studies established that during the polymerization of HEMA/PVP compositions in the presence of Fe 2+ ions, copolymers are formed, which are characterized by a spatially cross-linked structure formed by blocks of HEMA grafted on PVP [ 57 ]. Due to the presence of hydrophilic groups in the structure of the polymer matrix (hydroxyl HEMA and peptide PVP), pHEMA-gr-PVP copolymers [ 57 ] and metal-filled composites based on them [ 48 ] are characterized by increased sorption capacity for water and other polar solvents. Sorption–diffusion and the characteristics of materials based on pHEMA-gr-PVP copolymers are provided by the developed porous structure of the polymer matrix ( Figure 1 ).…”

“…As the metal content in the copolymer increases, the swelling rate decreases ( Figure 2 b). The obtained results can be interpreted as an increase in the number of crosslinks of the spatial network; an increase in metal content causes a decrease in M C [ 48 ].…”

“…However, as metal content in the original composition increases, the physico-mechanical characteristics increase, while W continues to decrease. Obviously, an increase in strength and elasticity, as well as a decrease in the ability to absorb water, occurs due to an increase in the degree of crosslinking and the number of physical nodes in the polymer network [ 48 ].…”

“…Measurements of the electrical resistance of the samples in a dry state were carried out after their conditioning for at least 5 h at a temperature of 23 °C and a relative humidity of 50%. Specific volume resistivity was calculated as [ 48 ]: where R V is volume electrical resistance, Ω; S is the square of the sample, m 2 ; and h is sample thickness, m.…”

“…The authors of the article developed new composite hydrogel materials based on spatially cross-linked copolymers of polyvinylpyrrolidone (PVP) with 2-hydroxyethylmethacrylate (HEMA) (pHEMA-gr-PVP) filled with finely dispersed particles of metals and alloys of various nature [ 48 ]. The growing interest in polymer hydrogels based on polyHEMA has arisen primarily due to the fact that they demonstrate excellent biocompatibility, compatibility with blood, and low thrombogenicity [ 49 , 50 ].…”