Spectral and photophysical properties of the Rhodamine 6G dye in the polyurethane matrices differing in the synthesis method, chemical structure and polarity characteristics were studied when doped with silicon dioxide nanoparticles. Differences in the aerosil effects on the dye H-dimer formation, the dye monomer/dimer ratio and the polymer matrix polarity were observed for the low-polar aromatic polyurethane acrylate compared to the high-polar aliphatic polyurethane. Introduction of the aerosil nanoparticles into the polyurethanes was shown to improve the dye photostability and enhance its luminescence intensity, which provides possibilities for the development of more stable and efficient laser active elements.

A method for obtaining polyurethane (PU) materials based on a mixture of prepolymers with different compositions is proposed to extend and specifically control the temperature range of effective damping. The initial polyurethanes include PU-1, which contains prepolymer-1 based on an oligoester with M = 1500 and an aliphatic diisocyanate; and PU-2, which contains prepolymer-2 based on an oligoether with M = 1000 and an aromatic diisocyanate. Additionally, PU compositions based on mixtures of prepolymer-1 and prepolymer-2 in ratios of 70/30, 50/50, and 30/70 wt.% were synthesized. Light microscopy showed that the initial PUs have a homogeneous structure, while the base-mixed prepolymer PU compositions display a distinct heterophase structure. The damping efficiency of the synthesized PU materials was assessed through their viscoelastic properties obtained using the dynamic mechanical analysis (DMA). Specifically, the mechanical loss parameter (tan δ) was used to define the effective damping region as the temperature range where tan δ ≥ 0.3. The initial PUs exhibited effective damping within the temperature ranges of −28 °C to 2 °C for PU-1 and −5 °C to 42 °C for PU-2. The temperature range for effective damping in the mixed prepolymer PU compositions extends from −22 °C to 37 °C, covering a range where neither of the initial PUs alone exhibits high damping capacity. It has been demonstrated that the effective damping range of PU composites can be adjusted by changing the ratio of prepolymer-1 to prepolymer-2. Further research has shown that PU compositions based on a mixture of prepolymers form a more cross-linked network. This correlates with an increase in chemical cross-links between hardener molecules and topological entanglements among macrochains. Depending on their prepolymer ratio, the mechanical properties of PU composites are intermediate between those of PU-1 and PU-2. Therefore, producing PU materials from a mixture of prepolymers with different chemical compositions is an effective method for developing damping materials.

For the first time, the influence of the xanthene-type rhodamine dyes, Rhodamine 6G (RG) or Rhodamine B (RB), on the thermal resistance of two different sorts of polyurethane resins (PUR) has been elucidated. The PURs were prepared either by direct reaction of the toluene diisocyanate and poly-oxypropylene glycol prepolymer hardened by trimethylol propane (PU), or by a radical photo-polymerization reaction of oligourethane acrylate with benzoin isobutyl ether (PUA). A correlation between the chemical structure of the polymers and their thermal properties was established using Fourier transformed infrared spectroscopy (FTIR, 400–4000 cm–1), thermogravimetric analysis (TGA, 30–800 °C), and differential scanning calorimetry (DSC). The DSC analysis shows that neither PU nor PUA display any phase transitions or melting points over the temperature interval of –100–300 °С, which is characteristic of amorphous polymers. The TGA study indicates that the PUA polymer is more thermal-resistant than the PU due to increased number of crosslinking points between the hard and soft segments. Сompared to nondoped polymers, the dye-doped PU-RB shows clearly improved thermal stability. It is found that a small presence of the RB dye improves the PU thermal stability, on account of the formed covalent and hydrogen-bonded network structures, while the effect is much smaller for the RG dye due to the presence of bulky CH3 groups and carboxyl group absence hampering the bonding formation. PUA samples prepared by radical photopolymerization are almost not sensitive to the presence of the dye molecules.

This paper studies energy and time operation characteristics of a laser on a Nd3+:YAG crystal with passive Q-switches based on a dye-activated aliphatic polyurethane matrix with high radiation strength. A high efficiency of laser generation both in a free mode and at single pulse generation in the Q-switched regime is obtained using a samarium diffuse reflector with a BaSO4 filler. A single pulse energy and duration for the lasers with passive Q-switches based on organo-nickel complex BDN and polymethine dye IR-1061 in an aliphatic polyurethane matrix polymerized by the polycondensation method from 1.6-diisocyanatohexane, poly[di(ethylene glycol) adipate] and trimethylolpropane as starting components were compared. A powerful single pulse with an energy of ~1 J was obtained in the Q-switching mode using polymethine thiopyrylo-4-tricarbocyanine dye (IR-1061). The highly efficient Q-switching caused by the use of passive laser Q-switch based on the IR-1061 dye is shown to be due to its specific linear and nonlinear spectral properties.

Temperature effects on the initial transmission of the laser passive Q-switch based on the BDN dye-doped polyurethane matrix were investigated in wide temperature range from –60 to +60°C. The temperature behavior of the Q-switch initial transmission was analyzed since its characteristics determined significantly the parameters of laser generation. The measured output energy of a single pulse from the neodymium laser on the 4F3/2 → 4I11/2 transition was shown to be dependent on the mutual spectral location of the laser generation wavelength and the dye absorption band of the S0 → S1 electron transition.

Effects of xanthene dyes and aerosil nanoparticles on the structure and dynamic characteristics of the cross-linked polyurethane were investigated by the IR-spectroscopy, dynamic-mechanical analysis, and electronic paramagnetic resonance methods. Dye molecule presence causes self-association of urethane groups within polymer rigid segments, weaker interactions between urethane groups and flexible oligoether parts and increased oligoether mobility. Increased mobility of flexible segments by xanthene dyes provides the necessary beam strength due to compensating the nanofiller network effect. The most efficient polyurethane material in the radiation resistance is expected to be a polymer composite with the highest permeability and the lowest modulus of elasticity.

A comparison was carried out of the nature of intermolecular interactions, elastic properties and gas permeability of the crosslinked polyurethanes doped with xanthene dyes and original polyurethane using IR spectroscopy, dynamic mechanical analysis (DMA) and electron paramagnetic resonance (EPR). The introduced dye can be considered as useful microimpurity which, however, can affect the efficiency of the laser. In IR spectra of polyurethanes the complex band of stretching vibrations of C=O groups is sensitive to the nature of intermolecular interaction of urethane groups. From the analysis of that band it is shown that in the presence of dyes, self-association of urethane groups within the hard segment predominates and the interaction of urethane groups with the oligoether component decreases, which can contribute to increasing the mobility of the flexible component. A decrease in the dynamic storage modulus (E’) and a decrease in the glass transition temperature (Tc) of polyurethanes in the presence of dyes is shown by the DMA method. The results of both DMA and IR spectroscopy indicate a greater increase in the mobility of the elastic component with the introduction of the rhodamine B dye, covalently bound to the polyurethane chain. According to nitroxyl paramagnetic probe data the introduction of both rhodamine B and rhodamine 6G dyes into polyurethanes increases their permeability to vapors of low-molecular weight compounds, but rhodamine 6G has a more prominent effect on this characteristic. This is consistent with DMA data indicating a greater increase in the Mc value in the presence of rhodamine 6G in polyurethane. The obtained results make it possible to determine the optimal composition of the active laser medium and are important in assessing the radiation resistance of the polymer matrix. Its increase is facilitated by a decrease in the storage modulus and an increase in the gas permeability of the polymer, leading to a decrease in pressure in the area of local heating.

У статті розглянуті шляхи запозичення та адаптації інтернаціональних одиниць у сучасній чеській мові. Особлива увага присвячена інтернаціональним словотвірним елементам.

One of the ways to reduce the cost of a polymermaterial is to replace the weight part of its composition with a cheaper natural filler. In this work, the objects of study are polyurethane composites synthesized by the insitumethod, containing the mineralfiller kaolin from 10 to 40 mass parts. Filling with kaolin significantly lowers the price of polyurethane material, and its cost is reduced by almost 30 percent when the content of the filler is 40 mass parts. Morphological studies have shown that kaolin particles are uniformly dispersed in the poly­urethane matrix, but thereis a tendency for the iragglomerationas the filler concentration increases. Viscoelastic, mechanical, and thermal properties of polyurethane composites wer studied. The damping efficiency of polyurethane materials was estimated from the results of dynamic mechanical analysis. Itis found that the filler additions lightly decreases the effective damping temperature range of polyurethane composites, but their heat resistance and mechanical properties improve. The method of thermogravimetricanalysis was shown the presence of kaolin significantly changes the character of thermo-oxidative destruction of composites. The temperature interval of the intensive decomposition stage increases for filled systems and the temperature of the maximum rate of weight loss at the decomposition stage (Tmax) increases with increasing kaolin content. According to the results of mechanical studies, an increase in the kaolin content in polyurethanes leads to an increase in the storage modulus (E') and a significant decrease in the relative elongation (ε). Thus, filling with kaolin significantly reduces the cost of polyurethane composites and contributes to their expansion of functional properties due to increased heat resistance and improved mechanical characteristics.

Photooxidation processes during irradiation of the aerosil-filled polyurethane films, based on oligooxypropylene glycol, toluene diisocyanate and trimethylolpropane, for a use as the active media of solid-state lasers were investigated by means of the IR-spectroscopy and dynamic mechanical analysis (DMA) methods, depending on the inorganic dopant concentration (5 and 7 wt%). The IR-spectroscopic experiments showed that the introduction of aerosil slowed down these processes. Data from dynamic mechanical studies indicated that irradiation of aerosil-filled polyurethane matrices caused an increase in its structural heterogeneity and a drop of the elastic modulus. During irradiation of the polyurethane material with 7 wt% of aerosil, a partial destruction of the nanofiller spatial network was possible due to dispersion of the irradiation energy by the nanoparticles. The obtained results demonstrated a positive effect of the aerosil nanofiller on the polyurethane material stability under irradiation with an ultra-high pressure mercury lamp.

Polyurethane (PU) materials attract the interest of researchers for use in damping and vibration isolation. However, an undesirable property of pure polyurethane is a narrow temperature range of mechanical energy absorption. This study presented several ways to design damping PU materials based on two initial polyurethanes with different prepolymer compositions. The difference between the glass transition temperatures of initial PUs was 30 degrees C. One way of designing was to obtain PU material based on a mixture of the two different prepolymers. Another way was to fabricate two-layer composites from layers of different initial PUs. Two-layer PU composites were fabricated in such ways as by sequential formation layer by layer or by gluing individual films. Continuous materials with a good connection between the layers were formed. Fourier transform infrared spectroscopy, light microscopy, contact angle measurements, and tensile tests were used for PU materials characterization. Dynamic mechanical analysis was used to investigate the viscoelastic properties and evaluate damping ability. The temperature ranges of effective damping (tan d = 0.3) from-27 degrees C to 17 degrees C and from-5 degrees C to 42 degrees C were shown for initial PUs. One high loss factor maximum for mixed-base polyurethane was observed, and the temperature range of effective damping was from-20 degrees C to 32 degrees C. All designed two-layer composites were shown two loss factor maxima. Their effective damping occurred either in one temperature range (-25 degrees C to 29 degrees C) or in two (-24 degrees C to-14 degrees C and-7 degrees C to 37 degrees C), depending on the design of the composite. The advantage of polyurethane materials design ways such as mixed-base and two-layer composite is the ease of control of the temperature region of effective damping. Proposed polyurethane materials designs offer a new approach to developing high-performed damping materials.

The effect of the phenalenone dyes Ph510, Ph160 and Ph439 on the characteristics that determine the radiation resistance of polyurethane (PU) matrices in the active elements of solid-state lasers was analyzed. The experiments by the EPR method with a nitroxyl spin probe showed that changes in the dynamic characteristics of the considered PU materials in the presence of phenalenone dyes were small. Contrary to this, gas permeability of polymer matrices in the presence of various phenalenone dyes was observed to decrease or grow depending on the structure of the dye and polyurethane, as well as on the possibility of chemical interactions of the dye with polymer. The obtained results make it possible to choose such combinations of pairs "phenalenone dye-polyurethane", where the radiation resistance of the polymer matrix would be optimal.

Covalent bonding between the Rhodamine B xanthene dye and polyurethanes, containing different isocyanate fragments (hexamethylene diisocyanate and toluene diisocyanate) has been realized and studied. Effects of polyurethane isocyanate components, different by chemical structure, on spectral properties of the Rhodamine B have been studied and discussed. Spectral, photophysical and lasing characteristics of the Rhodamine B dye, incorporated to the polyurethane matrices are presented.

Luminescence spectral properties of the two symmetrical indocyanine dyes with different substituents near nitrogen atoms have been investigated in the polyurethane matrices. The analysis of the IR-spectra, measured for the product of a reaction between indolenine salt, being a terminal heterocyclic fragment in one of these dye molecules, and phenyl isocyanate, and this salt and isocyanate as single bulk compounds has shown possibility of covalent bonding between this indocyanine and polyurethane. Such covalent bonding of the dye with the polymer matrix results in improvement of its luminescence spectral properties, compared to the dye-polymer solutions.

AbstractThe work presents investigation results on the main operation parameters of laser active elements, based on the xanthene dye and polyurethane matrices, different by their physical properties. The polyurethanes of various chemical contents are studied, in order to reveal the possibility for their efficient applications as active media in the solid‐state dye‐doped laser elements. Due to the solvation effects, the proposed high‐polar aliphatic polyurethane matrix provides a considerable growth of photostability, efficiency, and operation lifetime for the laser dye‐doped elements.

Spectral, photophysical and generation properties of symmetrical cationic cyanine dyes have been investigated in the polyurethane matrices, similar by the structure, but different by the polymerization method. The cyanine dye doped polyurethane, synthesized by a polycondensation reaction, provides laser active elements with significantly improved photostability, efficiency and operation lifetime, compared to those for the polyurethane acrylate matrix, hardened by a radical photopolymerization method. Changing the liquid (ethanol) medium to polymers causes an increase of fluorescence quantum yield and efficiency. For the first time, covalent bonding between a cyanine dye and a polyurethane has been studied, and high fluorescence quantum yield and generation efficiency have been observed.

In this work, based on the results of dynamic mechanical studies, the damping efficiency of two-layer polyurethane (PU) composites designed by gluing two films of synthesized PU with different glass transition temperatures (Tg) was estimated. The damping efficiency was estimated by the parameters of the mechanical losses (tanδ) peak. To vary Tg, three types of PU with different chemical nature and structure were synthesized. The effect of an increase in the difference between the Tg of the initial PU (ΔTg) on the damping efficiency of the two-layer PU composites formed from them is analyzed. The effective damping temperature range (ΔT) was estimated as the temperature range under conditions tanδ ≥ 0,3 and tanδ ≥ 0,6. It was shown that at ΔТg = 7 °С a two-layer PU composite has one relaxation maximum, and its temperature range of damping efficiency expands in comparison with ΔТ for individual PU. Under the conditions ΔТg = 23 °С and ΔТg = 30 °С, two-layer PU composites exhibit damping efficiency in two temperature regions at tanδ ≥ 0,3, which provides an additional temperature range of effective damping. The essential role of the PU structure of each of the layers in the formation of a two-layer composite by gluing has been determined. Easier penetration of residues of the adhesive organic solvent into the surface of the PU film with a linear structure leads to plasticization of the corresponding layer in the composite and reduces Tg. It is shown that a two-layer structure can be used to solve specific problems related to the adjustment or broadening the effective damping temperature range.

In this work the influence of transition metal coordination compounds was analyzed on the EMI-shielding characteristics and permeability for a paramagnetic probe of polymer composites based on cross-linked polyurethane or incompatible polymer blend (simultaneous semi-IPN based on cross-linked polyurethane and linear poly(methylmethacrylate) filled in situ with conductive and/or magnetic filler. Cross-linked polyurethane/carbon nanotube composites, polymer blend/carbon nanotube composites and polymer blend/carbon nanotube/nickel composites contained of 1.5 wt% and 3 wt% of fillers were modified with Fe(3+)acetylacetonate or Cr(3+) acetylacetonate coordination compounds of different complexing ability. It was shown that opposite effect of Fe(3+) and Cr(3+) complexes on the phase separation in the polymer blend allows regulate the level of the multiple reflection of the electromagnetic wave at the interfacial boundaries as well as protective characteristics and permeability of the investigated systems. The shielding efficiency of chromium-modified composite in the frequency range of (25.8-37.5) GHz is up to 25 dB in the segregated polymer. It has been shown that the effect of conductive nanofillers on polymer loosening is opposite to that of magnetic fillers and is sensitive to the presence in the system of coordination complexing agent.

Interpenetrating polymer networks (IPN) are mixtures of two cross-linked polymers formed as a result of chemical reactions of in situ synthesis of components from single-phase initial mixtures. As a rule, due to the incompatibility of the components, a physical process of phase separation takes place with the formation of heterogeneous systems with insignificant interphase adhesion, which can have a negative effect on the physicochemical properties. To increase the compatibility of the components and to stabilize the systems, compatibilizers are introduced into the reaction mixtures. In this work the kinetics of the in situ formation of the components of polyurethane/poly(methyl methacrylate) interpenetrating polymer networks and the phase separation induced by chemical reactions in the presence of methyl methacrylate polymerization oligoazoinitiators in the reaction mixture were studied. Oligoazoinitiators contained fragments of a polyurethane chain also. It has been shown that the introduction of oligoazoinitiators of various chemical natures can control the process of IPN formation due to the formation of block copolymers during synthesis, which are compatibilizers of the mixture. They slow down the phase separation process and favor the formation of a finer IPN structure.