The electronic and magnetic properties of copolymers on the basis of methyl methacrylate-methacrylic acid and butyl acrylate, (MMA)-(IAA)-(BA), and magnetite Fe3O4 nanoclusters at concentrations of 25, 45 and 67 wt % have been studied. A sharp decrease in the superparamagnetic relaxation time of the magnetic moment of the magnetite clusters was observed at their concentration of 45 wt %. This decrease in the relaxation time is associated with the emergence of the percolation threshold, when the copolymer was doped with magnetite clusters, and with the appearance of the exchange interactions via conduction electrons. The magnetic anisotropy along the sample surface and perpendicular to the surface in strong magnetic fields observed for this concentration is associated with the exchange interaction as well. The magnetic anisotropy of samples in weak magnetic fields corresponds to the dipole-dipole interaction between magnetite nanoclusters.

Limited diffusion of the ferric hydroxide (ferrihydrite) nanoparticles in the polymeric network of the AG 50W-X2 sulfonated cation exchanger solvated with aqueous solutions of glycerol (70 and 90 wt.%) was studied in the temperature interval from 90 to 293 K. The Mössbauer spectra were obtained in three windows (250, 25, and 5 mm/s) because of large line broadenings observed in the experiment. The procedure of “seaming” of the time-dependent correlation functions <[Δx( t )] 2 > obtained by the Fourier transform analysis of the initial Mössbauer spectra made it possible to observe the behavior of the function in the extremely wide time range from 0.4 to 360 ns. The observed plateau of the function at long times is a direct proof of the limited nature of the motion. The experimental data were interpreted in the framework of physical models of limited diffusion.

Magnetic transitions in nanoclusters of iron oxyhydroxide in polymeric (sulfocationite) and biopolymeric (ferritin) matrices are studied in the 4.2-50 K range by gamma-resonance (Mossbauer) spectroscopy. The hydration effect on the magnetic phase transitions. Hydration and swelling of the sulfocationite ion-exchange resin lower the magnetic transition temperature in clusters by Delta T-c0 = 3-4 K. This effect is considered using the thermodynamic model of magnetic phase transitions in nanoclusters and explained by the excess pressure of about 10(9) Pa arising due to freezing of the system and water transformation into ice with a volume increase. The Delta T-c0 shift estimated within the thermodynamic model of magnetic phase transitions for nanoclusters of about 3 nm in diameter ranges between (0.1-1.0)Delta T-c0 (Delta T-c0 is the temperature of magnetic cluster transition) which does not contradict experimental data. A 70% ferrite hydration also reduces Delta T-c0 by three or four K, which is consistent with the thermodynamic estimates.

Dependences of the dynamics of hydrophilic polymeric nets of acrylate cation exchanger, sulfonated poly(styrenedivinylbenzene) cation exchanger, and hydrophobic poly(divinylbenzeneethylstyrene) sorbent on the degree of hydration were studied by the Rayleigh scattering of Mössbauer radiation (RSMR). Dependences of the integral elastic fraction of RSMR of the polymer—water systems on the water/polymer mass ratio were determined. In the case of the cation exchangers, a considerable decrease in the elastic fraction of RSMR of the polymer during hydration was established. A considerable increase in the mobility of the nets indicates their transition from a glassy state to an elastic state. It was established that the intramolecular mobility of the hydrophobic polymeric sorbent remains unchanged during its hydration, and it contains water culsters with the nonzero elastic fraction of RSMR in its finest pores.

Bound diffusion of ultrafine particles of FeIII hydroxide in the pores of a solvated polymeric sorbent has been discovered and investigated by Mössbauer spectroscopy. Particles with diameters of 30 Å <-d <- 90 Å were precipitated from an aqueous solution in the pores of the poly(divinylbenzene-ethylstyrene) “Porolas A” sorbent. The Mössbauer spectra obtained atyT > 250 K (i.e., above the crystallization and glass transition points of the liquid in the pores,viz., water or glycerol) were found to assume the shape of a superposition of broadened and nonbroadened components, which is characteristic of bound diffusion. Experimental data were treated in terms of two alternative models of bound diffusion,viz., in harmonic (Brownian overdamped oscillator) and rectangular potentials. The following values for the parameters of bound diffusion (diffusion coefficientD and diffusion displacementr) at room temperature were found: for glycerol,D = 0.3 · 10−9; 0.5 · 10−9 cm2 s−1 andr = 0.14; 0.38 Å for water,D > 2 × 10−8 cm2 s−1 andr = 0.22; 0.45 Å. Unlimited diffusion of particles in the solvated sorbent was not observed. No diffusion of the particles was observed in the dry sorbent.

Iron hydroxide particles with diameters of about 3 nm have been precipitated in a network of polymer chains of sulfonated polystyrene, cross-linked by divinylbenzene. The dynamics of these iron particles has been investigated by Mossbauer spectroscopy. The spectra were analyzed using a generalized Brownian oscillator model, in which the bound diffusion proceeds in an arbitrary potential. Samples with different degrees of cross-linkage have been investigated. The water content of the samples was varied, and the viscosity of the water was increased by the addition of sucrose solution. It can be shown that the size of the cages formed by the polymer chains essentially determines the type of diffusion. If the iron hydroxide particles have no free space, the dynamics is determined by the polymer network. With an increase of the free volume, the iron hydroxide particles show the typical behavior of bound diffusion in a hard cage. By increasing the size of the cage further, one attains a situation close to free diffusion. Varying the viscosity of the solvated liquid in a sample with a given cage size leads to a dynamics of the iron hydroxide particles that shows the expected dependence on the diffusion constant D. It should be noted that some of the samples show unusually broad Mossbauer spectra, with a half width up to 500 mm/s.

The iron containing corrosion products from water heat-carrier and deposits of the second circuit of the nuclear power plant were investigated by means of absorption Mössbauer spectroscopy. The nonstoichiometric magnetite and paramagnetic (superparamagnetic) iron oxide particles were found to be the main corrosion products. The fraction of the magnetically ordered phase varied in the range 0–100% depending on the location in the second circuit.

In this survey, the scales and correlation times of the motion of iron atoms in the active site of myoglobin and hemoglobin, in the iron containing core, in iron storage proteins, and model polymer systems, and the average fragmental motion of protein globules of myoglobin and human serum albumin are considered. Models of intramolecular protein mobility are presented.

The mechanism of combustion of double-base rocket propellants containing iron and tin oxides was studied. By means of Mössbauer spectroscopy it has been established that the essential accumulation of the catalysts and the partial reduction of the initial oxides occurred in the zone above the combustion surface. The efficiency of additives action is influenced by SnO2 and α-Fe2O3 concentrations in this zone. The calculation of the heat balance showed the zone above the combustion surface to be the leading zone during combustion of the propellants containing the catalysts.

Bound diffusion of ultrafine particles of ferric hydroxide precipitated inside the polymeric cross-linkage degree the experimental spectra reveal a striking broadening up to hundreds of mm/s. This is a consequence of the crossover from the diffusion of a Brownian oscillator to free diffusion in restricted volume, the spatial displacements of the particles depending on the cross-linkage and changing from 0.1 to 0.6 Å.

In the survey, the scales and correlation times of motion on different levels are considered: iron atoms in active centre of myoglobin and hemoglobin, iron containing core in iron storage proteins and model polymer systems, and the average fragmental motion of a protein globule of myoglobin and human serum albumin. The models of intramolecular protein mobility have been drawn.

Relaxation Mössbauer spectra of two57Fe3+-exchanged acrylate cation-exchangers (SGK-7 and SG-1M, USSR) with various cross-linkage concentrations 2.5–16 mol.% were observed in windows of observation up to 250 mm/s. The frequencies of slow (ω≲10 s−1) intramolecular motions (displayed in Mössbauer lineshape) and the values of high frequency (ω≳10 s−1) atomic displacements (reflected in thef’ factor) decrease with the increase of cross-linkage concentration.

Simple model systems with pronounced dynamical features will help to get a deeper insight into the complicated dynamics of large molecular networks. We investigated the bounded diffusion of ultrafine Fe(OH)3 particles (∼30 Å in diameter) in the three-dimensional network of the cation exchanger Dowex 50 W which was solvated with a water solution of sucrose (60 wt%). Mössbauer spectra were recorded in the temperature range from 80 K to 305 K. At temperatures above 250 K broad diffusional lines of different widths appear in the spectrum proving the bounded nature of the diffusion. The line widths strongly increase with temperature to values of several hundred mm/s. Around 300 K a large portion of the area escapes even from the largest window of observation used in our experiments (±550 mm/s).

We have studied the bound diffusion of ferric hydroxide ultrafine particles imbedded in a solvated polymeric network of Dowex 50W - x1,2 cation exchangers. The Mössbauer experimental data were theoretically treated as continuous diffusion in an arbitrary potential. The shape of this potential was reconstructed from the temperature dependence of the Mössbauer lineshape.