It is shown that during the copolymerization of methyl methacrylate with the surfactant comonomer α,ω-dipropylmethacrylatep olidimethylsiloxane with the number of repeating dimethylsiloxane units n = 20 (DPMPDMS), strong interfacial adsorption layers are formed on the surface of polymer–monomer particles formed from microdrops, ensuring the stability of particles to various types of influences.

The composite films of phenyl/phenyl end-capped tetraanilineemeraldinesalt (TANI-ES) and nanocrystalline silicon (nc-Si) TANI-ES/nc-Si wereobtained using a drop-casting method by deposition from the solutionsonto the substrates with metal electrodes. A comprehensive analysisof the impedance spectra of the TANI-ES/nc-Si composite film at thetemperature range of 20-130 & DEG;C has been carried out. Forthe first time, it was found that there are two temperature rangesin which the impedance spectra are completely different. At the borderof these ranges at temperature T* & AP; 101.5 & DEG;C, the impedance spectra exhibit a pronounced inductive character.Differential scanning calorimetry (DSC) measurements showed that twophase transitions occur in the TANI-ES/nc-Si composite at temperaturesof 94 and 145 & DEG;C. An analysis of X-ray diffraction patterns revealedthat the crystal structure of the TANI-ES/nc-Si composite is unstableupon heating to 140 & DEG;C in a nitrogen atmosphere, and the degreeof this instability depends on the ratio of the number of TANI moleculesper one nanoparticle. The temperature dependence of the DC conductivitychanges sharply at a temperature of about 100 & DEG;C. The temperaturedependences of the fitting parameters used to fit the experimentalimpedance curves also change significantly at 100 & DEG;C. Such changesin the electrical characteristics can be explained by a second-orderphase transition in the TANI-ES/nc-Si composite at temperatures ofabout 100 & DEG;C. The Nyquist plot of the impedance of the TANI-ES/nc-Sicomposite has an inductive character at T* & AP;101.5 & DEG;C, and we believe that such a character may indicate aphase transition in this composite. The conductivity spectra of theTANI-ES/nc-Si film at all investigated temperatures, except for 101.5 & DEG;C, are well approximated by the sum of the power law, polaron,and DC conductivities. However, the film conductivity at T* & AP; 101.5 & DEG;C has a local maximum at about 10 Hz, andthis maximum cannot be approximated by standard functions used inimpedance spectroscopy to fit conductivity curves in the RF region.It has been shown for the first time that a good approximation isthe Drude-Smith formula, which has been successfully used toapproximate conductivity spectra in the terahertz range of the spectrum.An exact approximation of the spectra & epsilon;& PRIME;(& nu;) and & epsilon;& DPRIME;(& nu;) in the entire temperature range, except fortemperature T*, is achieved by a combination of theDebye and Cole-Cole functions and the component determinedby free charges. At temperature T*, in order to approximate the spectra & epsilon;& PRIME;(& nu;) and & epsilon;& DPRIME;(& nu;), in additionto the indicated combination of functions, it is also necessary touse the Drude-Smith function.

This article presents the results of investigations on heterophase polymerization of vinyl monomers in the presence of organosilicon compounds of different structures. On the basis of the detailed study of the kinetic and topochemical regularities of the heterophase polymerization of vinyl monomers, the conditions for the synthesis of polymer suspensions with a narrow particle-size distribution using a one-step method have been determined.

Polymerizable water-insoluble surface-active macromers (SAMs), namely alpha,omega-divinylpolydimethylsiloxane (DVPDMS), alpha,omega-dipropylmethacrylatepolydimethylsiloxane (DPMPDMS) and alpha,omega-pair(vinylbenzyl)polydimethylsiloxane (PVBPDMS), were synthesized and characterized using NMR. The colloidal-chemical properties of the synthesized compounds were studied in comparison with non-polymerizable polydimethylsiloxane. Using DVPDMS, DPMPDMS and PVBPDMS as copolymerizable emulsifiers, polystyrene and poly(methyl methacrylate) suspensions with large particles, narrow particle size distribution and with the absence of the residual surfactant in the waste water were obtained. It is shown that in the presence of DPMPDMS it is possible to obtain polymer suspensions with an average particle diameter of 1.6 mu m. The proposed mechanism of the effects of the SAMs on the polymerization is based on the copolymerization with the main monomers in the monomer-polymer particle interphases which results in stabilization of the particle protective layers from early stages of the reaction. (c) 2021 Society of Chemical Industry

In this study Langmuir films have been formed from emeraldine base and emeraldine salt forms of phenyl/phenyl-capped tetraaniline at the air/water and air/(camphorsulfonic acid water solution) interfaces respectively. Significant effect of tetraaniline protonation on its behavior in Langmuir films was revealed by measuring surface pressure and surface potential vs area per molecule isotherms and by Brewster angle microscopy. Multilayered tetraaniline Langmuir-Schaefer films of various thickness were transferred on silica substrates and the morphology of these films was analyzed by atomic force microscopy. Organic electrochemical memristive devices were assembled using the thin-film tetraaniline-based materials as well as a solid polymer electrolyte (polyethylene oxide doped with lithium perchlorate) and a silver counter electrode. Memristive devices have demonstrated resistive switching for at least 30 cycles and were characterized by the Rmax/Rmin ratio equal to 4.5.

Wide application of chitosan in modern technologies is limited by the lack of reliable and low-cost techniques to prepare size-tuned constructs with a complex surface morphology, improved optical and mechanical properties. We report a new simple method for preparation of transparent thermoreversible chitosan alcogels from chitosan/H2O/ethanol ternary systems. This method, termed "low temperature thermally induced phase separation under non-freezing conditions" (LT-TIPS-NF), fine tunes gelation by adjusting only temperature (from 5 to -25 °C) and varying the initial content of chitosan (from 0.5 to 2.0 wt%) and ethanol (from 28.5 to 47.5 vol%). Transparent non-swelling final constructs of complex shape are prepared by fixing the pre-formed alcogels with a base solution. The size of the gel constructs is limited only by the dimensions of the mold and the cooling chamber. The LT-TIPS-NF is applicable both in injection molding and 3D printing techniques. The in vitro and in vivo experiments show the absence of prominent cytotoxicity and well-defined cell adhesion on the obtained hydrogels. Thus, this facile and scalable technique provides the multifunctional chitosan gel preparation with easily controlled properties exploiting inexpensive, renewable, and environmentally friendly source polysaccharide. These materials have prospects for a variety of uses, especially for biomedical applications.

Materials based on hyaluronic acid (HA) are extensively used in tissue engineering as scaffolds. Photoinduced crosslinking is one way to prepare them, and, for this, HA must be modified with vinyl groups, which are capable of participating in free-radical reactions upon exposure to light. The quantity of grafted vinyl groups, represented as the degree of substitution (DS), is an important parameter of modified HA (mHA) that is related to the mechanical, chemical, and biological properties of scaffolds. Here, we demonstrate the feasibility of tuning DS by varying the reaction parameters (composition and concentration of reaction components and reaction conditions) and investigate the effect of DS on the viscosity of mHA solutions. As example, we consider the photoinduced reaction of mHA in the presence of flavin mononucleotide as the initiator, which can be used in fabrication of noncytotoxic scaffolds by 3D printing. The growth behavior of fibroblasts on the scaffold surface is studied.

In the late 1990s, the unique possibilities application of inorganic nanocrystals with anti-Stokes photoluminescence were demonstrated. In a fairly short period, a significant breakthrough has been achieved in this field due to the development of new and modification of existing methods for the synthesis of these nanomaterials, and the expansion of understanding of the photophysical processes occurring in nanocrystals. The interest from the scientific community is due to the exceptional luminescence properties of upconversion nanomaterials, which can convert photons of the near-infrared spectrum to radiation in the visible and UV ranges. This multiquantum process takes place under low-intensity excitation, which largely determines the use of this class of nanomaterials in high-tech fields, including biotechnology, photochemistry, medicine, solar energy, nanosensorics, etc. The goals of this review are to consider the mechanisms of anti-Stokes luminescence, to analyze the synthesis methods, and to demonstrate the applications of fluoride upconversion nanomaterials, in which they have formed a stable scientific and technological niche.

Objectives. This paper presents data on the development and study of the structural properties of iron-doped crystalline silicon (nc-Si/SiOx/Fe) nanoparticles obtained using the plasma-chemical method for application in magnetic resonance imaging diagnostics and treatment of oncological diseases. This work aimed to use a variety of analytical methods to study the structural properties of nc-Si/SiOx/Fe and their colloidal stabilization with citrate anions for in vivo applications.Methods. Silicon nanoparticles obtained via the plasma-chemical synthesis method were characterized by laser spark emission spectroscopy, atomic emission spectroscopy, Fouriertransform infrared spectroscopy, and X-ray photoelectron spectroscopy. The hydrodynamic diameter of the nanoparticles was estimated using dynamic light scattering. The toxicity of the nanoparticles was investigated using a colorimetric MTT test for the cell metabolic activity. Elemental iron with different Fe/Si atomic ratios was added to the feedstock during loading.Results. The particles were shown to have a large silicon core covered by a relatively thin layer of intermediate oxides (interface) and an amorphous oxide shell, which is silicon oxide with different oxidation states SiOx (0 ≤ x ≤ 2). The samples had an iron content of 0.8–1.8 at %. Colloidal solutions of the nanoparticles stabilized by citrate anions were obtained and characterized. According to the analysis of the cytotoxicity of the modified nanosilicon particles using monoclonal K562 human erythroleukemia cells, no toxicity was found for cells in culture at particle concentrations of up to 5 µg/mL.Conclusions. Since the obtained modified particles are nontoxic, they can be used in in vivo theranostic applications.

The review considers the role that nanotechnologies play in the development of sample preparation methods for molecular diagnostic, focusing on the methods to isolate nucleic acids (NAs) from biological samples and the underlying physicochemical processes. Methods based on reversible adsorption (that is, solid-phase selective extraction) are the most efficient and allow miniaturization and automatization of the related processes. In the approach most commonly used until recently, NAs from biological samples are bound with a sorbent and then eluted (positive selection). The review analyzes the potential and advantages of an alternative one-step NA isolation method. Sorbents utilized in the method bind proteins and other components of biological samples, but are inert towards NAs in terms of absorption (negative selection). Consideration is given to the methods used to produce nanostructured composite sorbents on the basis of solid matrices (porous silica, glass multicapillaries, and synthetic membranes) via modification with nano-thick polymer layers to achieve negative selection toward NAs. Primary attention is payed to fluoropolymers and polyanilines, their applications, and fields of their alternative use.

Polyaniline (PANI) is a polyconjugated polymer that attracts the attention of scientists for many years because of the possibility of its use in both organic electronics and as material for biomedical and electrophysical application, thanks to its high conductivity, chemical stability, the ability of redox and non-oxidative doping, biocompatibility and selective affinity for different types of biopolymers. However, volatility of physical and chemical properties of PANI limits its wide practical application as a component of composites. Those drawbacks could be overcome by the use of aniline oligomers that demonstrate reliable control and adjustment of their structure, better solubility and processability. In this research, we examined physical and chemical properties of phenyl end-capped tetraaniline (TANI) and its films, which are the lowest molecular weight derivatives of aniline in comparison with PANI. Self-organized thin film structures of TANI with well-defined morphology were prepared via transfer of Langmuir films obtained on the water-air interface. The behavior of TANI as bioseparating material as studied with spectral correlation technique on the examples of separation of nucleic acids and proteins was shown to be similar to PANI?s behavior. In particular, TANI demonstrates sorption inertness towards double strained nucleic acids and binds the proteins depending on their isoelectric points and hydrophobicity (?negative selection?).

It is well-known, due to the geological features in a number of regions of the Russian Federation, there may be a shortage of certain microelements and other important “nutrients” in animal diets. The main approach to solve this problem is to use special feed additives. At present, preparations based on organic sources, for example, metal-polymer complexes, are considered a promising alternative. The purpose of this study is to develop an improved method for preparation of the copper-containing polysaccharide complexes and to study their most important parameters. Using CuCl2 as an example, it was shown that the formation of chitosan hydrogels is possible without the usage of potentially hazardous cross-linking agents (for example, glutaraldehyde) or polyvalent anions (for example, SO4 2–), which provide non-covalent cross-linking of chitosan due to electrostatic interactions with NH3 + in its composition. It was found that, upon frontal «gelation» of a 2% chitosan solution (MM 400±100 kDa) in acetic acid (1 vol%), the formation of stable metal gels is observed provided that the content of CuCl2 and ethanol in the precipitant solution is more than 40 mg/ml or more than 24 vol.%, respectively (Vchitosan = Vprecipitant). The obtained complexes are stable in aqueous-alcoholic solutions and swell in water up to destruction (pH 5,5). After additional treatment with an aqueous 1,5% ammonia solution, complexes practically do not swell in solutions with ≥ pH 5,5 (at least τ = 6 days) and dissolve at pH ≤ 4,2. Thus, the use of these complexes is able to provide the release of Cu2 + not in the rumen (pH 6,3–7,2), but in the abomasum (pH ~ 3), which can increase the bioavailability of copper. The development of an improved method for obtaining metal-polysaccharide complexes in a gel form that does not contain «ballast» (in terms of nutritional value and physiology of farm animals) anions (for example, SO4 2–) opens up new opportunities for the development of highly effective feed additives for animal husbandry.

In this study, a new method for production of hydrogels with oriented multichannel structure based on chitosan-poly(vinyl alcohol) compositions was developed. Microscopic and biological studies of the obtained hydrogels were conducted to determine the optimal composition, which would ensure that structure of the material mimics that of the epineurium and perineurium in a nerve. Structure of the hydrogels was adjusted by variation of the initial concentration of the precipitant, poly(vinyl alcohol), and acid in the chitosan compositions. A single cycle of freezing and thawing of the produced hydrogels resulted in lower structural heterogeneity, which is promising for the production of a scaffold that simulates the structure of the native peripheral nerve. in vitro cytotoxic assays showed biocompatibility of the manufactured hydrogels.

In this paper, it is proposed to use polymer-modified composite materials based on nanocrystalline silicon (nc-Si) as an alternative to organic fluorescent quantum dots traditionally used in medicine. A distinctive feature of nc-Si is a high absorption coefficient in the near UV and blue-violet range and the ability to transmit light in the visible region of the spectrum. The main advantage of silicon-based nanoparticles for in vivo use is their biodegradability and the absence of toxic properties. For hydrophilization of silicon nanoparticles, their surface was modified by amphiphilic biocompatible polymers: polyvinylpyrrolidone, a copolymer of maleic anhydride and 1-octadecene, cremophore, which is a polyoxyethylene derivative of hydrogenated castor oil. Silicon nanoparticles (nc-Si) with an average diameter of 4.5 nm, synthesized by annealing of SiO at 1150 °C, and functionalized with 1-octadecene photoluminescent in the red-infrared spectral region were used. The presence of the polymer shell on the surface of the nanoparticles was confirmed by FTIR spectroscopy. The sedimentation and aggregative stability of the particles in water were analyzed. It is shown that after the nc-Si polymer modification, the photoluminescent properties of nanoparticles are retained although the photoluminesce maxima were shifted to the blue region. Colorimetric MTT-assay of the cytotoxicity of the nanoparticles modified with polymers to monoclonal cells of human erythroleukemia K562 showed no toxicity for cells in culture at a particle concentration of up to 50 μg/ml. Subcellular localization of silicon nanoparticles into the human cervical carcinoma cell line HeLa was shown by means of fluorescence microscopy. The obtained polymer-modified nc-Si particles can be recommended for the purposes of bioimaging in in vitro and in vivo applications.

The detection of double bonds in polymers exploited as scaffold materials, e.g. hyaluronic acid (HA) derivatives, is crucial for their further applications. The quantity variations of unsaturated units significantly affect the photoinduced crosslinking degree responsible for the mechanical properties of scaffolds. We demonstrate a simple, selective and rapid quantitative method that enables the detection of double bond moieties in polymers. The approach is based on a reaction with potassium permanganate which is spectrophotometrically confirmed. The effect of glycidyl methacrylate concentration and various reaction catalysts introduced at the stage of HA modification, as well as the change of double bond concentration over time, has been investigated using the proposed method. In addition, the developed quantitative method can be utilized for rapid and efficient detection of unreacted double bonds after photopolymerization as a tool for monitoring conversion over time.

Modern approaches to the preparation of monomers and polymers based on benzocyclobutene are considered. The groups of polymers containing siloxane, silyl, polyfluorinated fragments, polyimides, polyamides, polyacrylates, polyolefins, and polyarylenes are distinguished among benzocyclobutene-containing polymers. The basic properties of these polymers (glass transition temperature, decomposition onset temperature, dielectric properties, moisture resistance) are described, and the possibility of their application in the creation of microelectronics devices is evaluated. It has been established that the dielectric constant of most known benzocyclobutene-based polymeric materials lies in the range from 2.3 to 3.07. Fluorine-containing and organosilicon derivatives show the best dielectric properties (2.3–2.38). Polysiloxanes possess the highest thermal stability between considered polymers, demonstrating stability up to 500–550 °C both in inert atmosphere and in air.