Features of Structure and Properties of pHEMA-gr-PVP Block Copolymers, Obtained in the Presence of Fe2+

Abstract

This paper presents the research results of the copolymer structure and properties of 2-hydroxyethylmethacrylate (HEMA) with polyvinylpyrrolidone (PVP) and their hydrogels, obtained by block polymerization in the presence of iron sulfate (II). By the methods of chemical analysis, IR spectroscopy, Thermogravimetric (TG) and Differential Thermal Analysis (DTA), the course of grafted copolymerization of HEMA on PVP with the formation of a cross-linked copolymer was confirmed. The results received by scanning electron microscopy showed that due to the copolymerization of HEMA with PVP, macroporous hydrogels with a pore size of 10–30 μm were obtained. The peculiarities of the structure formation of the obtained copolymers depending on the initial composition formulation were established and their structural parameters were investigated: PVP grafting efficiency, PVP content in copolymer, molecular weight of internodal fragment of polymer network, crosslinking degree, and crosslinking density. The interrelation of sorption–diffusion, physical–mechanical and thermophysical properties along with the structure of the obtained materials was proved. It was shown that with the increasing PVP content in the original composition, the efficiency of its grafting and crosslinking density of the polymer network decreased, but the surface hardness, heat resistance, sorption capacity of copolymers in the dry state, as well as ion permeability and elasticity in the swollen state increased, while their tensile strength deteriorated. It is proved that by changing the original composition formulation it is possible to change the structure and hence the properties of the copolymers in the desired direction.

New Materials Based on Polyvinylpyrrolidone-Containing Copolymers with Ferromagnetic Fillers

“…Copolymerization of HEMA with PVP was carried out in bulk with the presence of iron sulfate (II) at room temperature [ 42 ]. The calculated amount of PVP and FeSO 4 were weighed according to the given formulation.…”

“…Solutions of FeSO 4 and PVP in HEMA were mixed to obtain a homogeneous mixture, without insoluble agglomerates and mechanical inclusions, which was processed by the casting method into a polymerization mold. The obtained products were rinsed in distilled water until there was complete removal of unreacted HEMA and PVP [ 42 ].…”

“…Determination of heat resistance of copolymers was carried out according to the method ISO 306:2013 “Plastics—Thermoplastic materials—Determination of Vicat softening temperature”, which consisted of determining the temperature at which a standard indenter, with a flat bottom surface (Ø 1.128 ± 0.008 mm), was pressed under the action of the load to a depth of 1 mm in the test sample, which was heated at a constant speed. Studies were performed by using a Höppler consistometer [ 42 ].…”

“…The role of PVP complexes with vinyl monomers is particularly noteworthy [ 41 ]. Specifically, this ability has a significant impact on the kinetics of polymerization of HEMA in the presence of PVP (through the formation stage of a complex with charge transfer) and the formation of the polymer matrix structure [ 42 ]. At the same time, the use of PVP opens up additional opportunities for modification of various substances [ 43 , 44 ] and improvement of technologies for obtaining new functional materials with a set of unique properties [ 45 , 46 ].…”

“…The work [ 42 ] presents the study results of the structure and properties of pHEMA-gr-PVP copolymers and their hydrogels obtained by bulk polymerization in the presence of ferrous sulfate (II). The course of grafting polymerization of HEMA on PVP with the formation of a crosslinked copolymer was confirmed by chemical analysis, IR spectroscopy, TGA and DTA.…”