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This study presents preparing and characterization of polyacrylonitrile (PAN) fibers containing various content of tetraethoxysilane (TEOS) incorporated via mutual spinning solution or emulsion using wet and mechanotropic spinning methods. It was shown that the presence of TEOS in dopes does not affect their rheological properties. The coagulation kinetics of complex PAN solution was investigated by optical methods on the solution drop. It was shown that during the interdiffusion process phase separation occurs and TEOS droplets form and move in the middle of the dope’s drop. Mechanotropic spinning induces the TEOS droplets to move to the fiber periphery. The morphology and structure of the fibers obtained were investigated by scanning and transmission electron microscopy, as well as X-ray diffraction methods. It was shown that during fiber spinning stages the transformation of the TEOS drops into solid silica particles takes place as a result of hydrolytic polycondensation. This process can be characterized as the sol-gel synthesis. The formation of nano-sized (3–30 nm) silica particles proceeds without particles aggregation, but in a mode of the distribution gradient along the fiber cross-section leading to the accumulation of the silica particles either in the fiber center (wet spinning) or in the fiber periphery (mechanotropic spinning). The prepared composite fibers were carbonized and according to XRD analysis of carbon fibers, the clear peaks corresponding to SiC were observed. These findings indicate the useful role of TEOS as a precursor agent for both, silica in PAN fibers and silicon carbide in carbon fibers that has potential applications in some advanced materials with high thermal properties.

An experimental quasi-equilibrium phase diagram of the polyvinylidene fluoride (PVDF)–camphor mixture is constructed using an original optical method. For the first time, it contains a boundary curve that describes the dependence of camphor solubility in the amorphous regions of PVDF on temperature. It is argued that this diagram cannot be considered a full analogue of the eutectic phase diagrams of two low-molar-mass crystalline substances. The phase diagram is used to interpret the polarized light hot-stage microscopy data on cooling the above mixtures from a homogeneous state to room temperature and scanning electron microscopy data on the morphology of capillary-porous bodies formed upon camphor removal. Based on our calorimetry and X-ray studies, we put in doubt the possibility of incongruent crystalline complex formation between PVDF and camphor previously suggested by Dasgupta et al. (Macromolecules 2005, 38, 5602–5608). We also describe and discuss the high-temperature crystalline structure of racemic camphor, which is not available in the modern literature.

Herein we present a Ca[EDTA]-based synthesis and comparative study of perfectly shaped plate-like, rod–like, and prism-like carbonated apatites.

The influence of the structure of the polymer matrix on the main photoluminescence characteristics of composites based on core (CdSe) and core–shell type (CdSe/ZnS) quantum dots embedded in liquid-crystalline and amorphous polymers of similar chemical structure is studied. The photoluminescence spectra consist of two bands (2.15 and 1.70 eV), the first of which corresponds to the radiative recombination of excitons, and the second one corresponds to carriers captured by traps at the quantum dot boundary. The second band is absent in the case of CdSe/ZnS quantum dots embedded in the liquid-crystalline polymer matrix. The kinetics of photoluminescence is well described by the sum of two decaying exponentials for CdSe quantum dots in matrices of both types and CdSe/ZnS quantum dots in the amorphous matrix. To determine the photoluminescence kinetics in the case of CdSe/ZnS quantum dots in the liquid-crystalline matrix, one exponential is sufficient. These effects are explained by the appearance of regions with closely spaced quantum dots, in which, in particular, the resonance transmission of excitation is possible.

Different forms of 6-О-carboxymethyl chitin were prepared, namely, the salt form containing, the carboxy group in the –COONa form, the acid form containing the carboxy group in the –COOН form, and the mixed form containing the units in the acid and salt forms in the equimolar ratio. The composition and structure of the synthesized carboxymethyl chitin and films based on them were confirmed by Fourier IR spectroscopy, solid-state 13C NMR spectroscopy, thermal gravimetric analysis, and differential scanning calorimetry. The mechanical properties of the films prepared from 6-О-carboxymethyl chitin in the salt and acid forms were evaluated by comparing their deformation characteristics. The Fourier IR data confirm formation of hydrogen bonds and ion pairs in 6-О-carboxymethyl chitin in the acid form as a result of intermolecular interaction of functional groups of the polymer. The solid-state 13С NMR data show that the substitution of the –СН2СООNa group for hydroxyl proton in the course of the synthesis of 6-О-carboxymethyl chitin from chitin occurs exclusively at the С-6 atom of the glucopyranose ring. Comparison of the data of thermal gravimetric analysis and differential scanning calorimetry shows that the amount of water absorbed by the polymer depends on the form in which 6-О-carboxymethyl chitin occurs, with the salt form being the most hygroscopic. The deformation characteristics of films of 6-О-carboxymethyl chitin in the salt and acid forms were studied. The elastic modulus of 6-О-carboxymethyl chitin in the acid form significantly differs from that of 6-О-carboxymethyl chitin in the salt form. This difference may be due to higher content of water absorbed by the polymer in the films obtained from the salt form of 6-О-carboxymethyl chitin (20%) compared to the films obtained from the acid form of 6-О-carboxymethyl chitin (9%).

Fluorinated polymers are attractive due to their special thermal, surface, gas separation, and other properties. In this study, new diblock, multiblock, and random copolymers of cyclooctene with two fluorinated norbornenes, 5-perfluorobutyl-2-norbornene and N-pentafluorophenyl-exo-endo-norbornene-5,6-dicarboximide, are synthesized by ring-opening metathesis copolymerization and macromolecular cross-metathesis in the presence of the first- to third-generation Grubbs’ Ru-catalysts. Their thermal, surface, bulk, and solution characteristics are investigated and compared using differential scanning calorimetry, water contact angle measurements, gas permeation, and light scattering, respectively. It is demonstrated that they are correlated with the chain structure of the copolymers. The properties of multiblock copolymers are generally closer to those of diblock copolymers than of random ones, which can be explained by the presence of long blocks capable of self-organization. In particular, diblock and multiblock fluorine-imide-containing copolymers show a tendency to form micelles in chloroform solutions well below the overlap concentration. The results obtained may be of interest to a wide range of researchers involved in the design of functional copolymers.

Commercial metathesis polynorbornene is used for the fabrication of high-damping coatings and bulk materials that dissipate vibration and impact energies. Functionalization of this non-polar polymer can improve its adhesive, gas barrier, and other properties, thereby potentially expanding its application area. With this aim, the post-modification of polynorbornene was carried out by inserting ethylene–vinyl acetate–vinyl alcohol blocks into its backbone via the cross-metathesis of polynorbornene with poly(5-acetoxy-1-octenylene) and subsequent deacetylation and hydrogenation of the obtained multiblock copolymers. For the first time, epoxy groups were introduced into the main chains of these copolymers, followed by the oxirane ring opening reaction. The influence of post-modification on the thermal, gas separation, and mechanical properties of the new copolymers was studied. It was shown that the gas permeability of the copolymer significantly depends on its composition, as well as on the amounts of hydroxyl and epoxy groups. The developed methods efficiently improve the barrier properties, reducing the oxygen permeability by 15–33 times in comparison with polynorbornene. The obtained results are promising for various applications and can be extended to a broader family of polydienes and other polymers containing backbone double bonds.

New norbornene-based functional multiblock copolymers containing ethylene–vinyl acetate/vinyl alcohol sequences are synthesized via the olefin cross-metathesis reaction of polynorbornene with poly(5-acetoxy-1-octenylene) followed by CC bond hydrogenation and acetoxy group deprotection. Macromolecular cross-metathesis, a recently developed type of interchange reaction, was carried out in the presence of Grubbs’ ruthenium catalysts and monitored by in situ1H NMR and ex situ13C NMR spectroscopy. This results in copolymer formation and its gradual randomization by segment reshuffling promoted by polymer-based Ru-carbenes. The kinetic study reveals that, despite the presence of bulky acetoxy substituents in polyoctenamer chains, Grubbs’ catalyst interacts with them more easily than with polynorbornene chains, which have cyclopentane rings in the backbone. The rate of the subsequent interchange reaction is controlled by the interaction of [Ru]-poly(5-acetoxy-1-octenylene) carbenes with norbornene units. It is found that the acetoxy groups markedly slow down the interaction of [Ru]-polynorbornene carbenes with the CC bonds in octenamer units. Since these carbenes are relatively unstable, they cause a noticeable decay of the reaction active centers. Our study demonstrates that the chain structure and, therefore, physico-chemical characteristics of multiblock copolymers can be tailored by adjusting the cross-metathesis conditions, such as the polymer concentration, polymer to catalyst ratio, and reaction time. Polymer-analogous reactions of hydrogenation and deacetylation transform octenamer units into ethylene–vinyl acetate/vinyl alcohol segments and thus open up more possibilities for tuning the thermal, gas barrier, and hydrophobic/hydrophilic properties of the synthesized norbornene-based multiblock copolymers.

The process of film formation including the initial treatment of thin layers of cellulose solutions in N-methylmorpholine N-oxide with isobutanol followed by washing with water is investigated in detail, and the structural and morphological features of the obtained films are examined. The phase state of the N-methylmorpholine N-oxide–isobutyl alcohol system is studied by differential scanning calorimetry and optical interferometry, and a diagram describing the crystalline equilibrium and allowing determination of the temperature–concentration “window” of compatibility of components is constructed. The dependence of viscosity of N-methylmorpholine N-oxide solutions in isobutanol on temperature confirms the phase composition of the system. The process of film formation is modeled by analyzing the diffusion zone of the cellulose solution–isobutyl alcohol system. The IR study of the interaction of N-methylmorpholine N-oxide containing 13.3% water with isobutanol shows that the affinity of isobutanol for water is much higher than that for N-methylmorpholine N-oxide. For this reason, when the spinning solution is brought in contact with isobutanol, the redistribution of water between the interacting components occurs and the structure of the heterogeneous gel-like complex cellulose–N-methylmorpholine N-oxide–isobutanol “is frozen,” as proved by the X-ray diffraction study of the films. Complete removal of the solvent and isolation of cellulose from this film proceed only upon subsequent washing with water. The X-ray diffraction and optical interferometry study of the effect of temperature on the interaction of a hot cellulose solution with cold isobutanol suggests that at room temperature the film obtained from solution contains inclusions of the vitrified N-methylmorpholine N-oxide. Under isothermal conditions (at a temperature of 90°С), the rate of interdiffusion grows appreciably and the solution preserves the homogeneous structure. Thus, the precipitation of cellulose from the bicomponent solvent N-methylmorpholine N-oxide–water upon contact first with isobutanol and then with water proceeds via two stages: initially the system undergoes phase separation and a concentrated solution is formed in the isobutanol-N-methylmorpholine N-oxide blend, from which cellulose precipitates upon interaction with water. When the process of primary interaction of the solution with alcohol is conducted under the conditions of compatibility of isobutanol with N-methylmorpholine N-oxide, a more homogeneous morphology of the films can be obtained.

The reaction of macromolecular cross-metathesis of polynorbornene and polydodecenamer catalyzed by the first-generation Grubbs Ru-carbene complex is studied for the first time. Polydodecenamer with high-molecular-weight characteristics (Mw = 406 × 103, Ð = 2.5) and a yield of 96% is synthesized by the ring-opening metathesis polymerization of cyclododecene mediated by the second-generation Grubbs catalyst. The polymer has a melting temperature of 62–83°C, depending on the content of trans double bonds, and shows poor solubility in organic solvents at room temperature. Its cross-metathesis with polynorbornene at 40°С gives rise to new statistical multiblock copolymers of norbornene and cyclododecene with different degree of blockiness. NMR, GPC, and DSC were used to investigate the effect of reaction conditions on the structure and thermal properties of the copolymers. At the initial step of the reaction, along with a high-molecular-weight peak, the GPC chromatograms exhibit a peak due to the low-molecular-weight fraction (M = (1–2) × 103), suggesting the formation of cyclooligomers. With increasing degree of interchain exchange, the proportion of the oligomeric fraction decreases appreciably. The kinetics of the cross-metathesis of polynorbornene with polydodecenamer and polyoctenamer at 40°С is studied by in situ 1Н NMR spectroscopy and ex situ 13С NMR spectroscopy. The rates of elementary reactions in these blends differ insignificantly, except for the conversion stage of the initial carbenes into polymer ones. The formation rate for carbene [Ru]=polyoctenamer is three times higher than the formation rate for the [Ru]=polydodecenamer carbene. In both cases, the fraction of Ru carbenes attached to norbornene units is extremely small throughout the process.

The macromolecular reaction of interchain cross-metathesis between polynorbornene and poly(5,6-epoxy-1-octenamer) in the presence of the first-generation Grubbs catalyst is studied. Chemically stable poly(5,6-epoxy-1-octenamer) is obtained through metathesis polymerization of 5,6-epoxycyclooct-1-ene with the second-generation Grubbs ruthenium catalyst. New random multiblock copolymers of norbornene and 5,6-epoxycyclooct-1-ene with different average block lengths determined by the reaction time, solvent type, and concentrations of the catalyst and initial homopolymers are synthesized and characterized by NMR, GPC, and DSC. Despite a distance between the epoxy substituent and the reaction center (double bond), poly(5,6-epoxy-1-octenamer) shows a lower activity in the cross-metathesis reaction with polynorbornene compared to unsubstituted polyoctenamer. The influence of epoxy groups present in the backbones of homopolymer and norbornene–cyclooctene multiblock copolymers on their thermal characteristics is studied. It is shown that the glass transition and melting temperatures increase with the concentration of epoxy groups upon the incorporation of an oxirane fragment into both homopolymers and copolymers. The crystallinity of poly(5,6-epoxy-1-octenamer) increases with the content of trans-С=С bonds in the polymer.

Using recently constructed experimental phase diagram isotactic polypropylene–1,2,4,5-tetrachlorobenzene (TeCB), we formulate a physically consistent scenario of the mixture evolution under thermally induced phase separation and predict the morphology of capillary-porous bodies that are formed after cooling down the binary system and removal of the low molecular mass component. This approach allows us to interpret the experimental data obtained by optical microscopy, scanning electron microscopy, and differential scanning calorimetry on the system with two crystallizable components. At any composition, TeCB forms needle-like crystals of nearly square section. Increasing polymer content affects crystal growth by limiting their length and by generating another population of small TeCB crystals of irregular shape and close to log-normal size distribution, located in the amorphous polymer regions. Finite rate of cooling the system leads to a hysteresis, when the values of characteristic temperatures and compositions in the phase diagram appear to be considerably shifted to lower temperatures and higher polymer contents. Combination of structural and calorimetric data provides an opportunity to characterize polymer–solvent systems from both thermodynamic and technological standpoints.

Embedding quantum dots (QDs) into an organic matrix of controllable order requires the identification of their structural characteristics. This analysis is necessary for the creation of anisotropic composites that are sensitive to external stimuli. We have studied the QD structures formed during the single-step synthesis of CdSe/ZnS QDs and their transformations after the initial ligand's substitution for another ligand. This single-step process leads to the formation of the core/shell structure. We detect the presence of two oleic acid residues ionically connected to Zn and Cd. At the same time, the amount of Cd oleate at the surface is very small. We observe the ligand exchange process at the surface of the core/shell QDs. The oleic acid residues are substituted by terphenyl-containing (TERPh-COOH) aromatic acid residues. The reaction between CdSe/ZnS carrying TOP and oleic acid residues ionically bound with QDs and terphenyl-containing acid leads to the coexistence of multiple ligands on the QD surface at a ratio of 11:6:33 for TOP/OA/TERPh-COOH.

Low-temperature properties of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and their blends were studied. The analyzed low-temperature mechanical properties involve the deformation resistance and impact strength characteristics. HDPE is a bimodal ethylene/1-hexene copolymer, LDPE is a branched ethylene homopolymer containing short-chain branches of different length, LLDPE is a binary ethylene/1-butene copolymer and an ethylene/1-butene/1-hexene terpolymer. The samples of copolymers and their blends were studied by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), 13С NMR spectroscopy, and dynamic mechanical analysis (DMA) using testing machines equipped with a cryochamber. It is proposed that such parameters as “relative elongation at break at −45 °C” and “Izod impact strength at −40 °C” are used instead of the ductile-to-brittle transition temperature to assess frost resistance properties because these parameters are more sensitive to deformation and impact at subzero temperatures for HDPE. LLDPE is shown to exhibit higher relative elongation at break at −45 °C and Izod impact strength at −20 ÷ 60 °C compared to those of LDPE. LLDPE terpolymer added to HDPE (at a content ≥ 25 wt.%) simultaneously increases flow properties and improves tensile properties of the blend at −45 °C. Changes in low-temperature properties as a function of molecular weight, MWD, crystallinity, and branch content were determined for HDPE, LLDPE, and their blends. The DMA data prove the resulting dependences. The reported findings allow one to understand and predict mechanical properties in the HDPE–LLDPE systems at subzero temperatures.

We investigate the structure–property relations of the multiblock copolymers of norbornene with cyclododecene synthesized via the macromolecular cross-metathesis reaction between amorphous polynorbornene and semicrystalline polydodecenamer in the presence of the first-generation Grubbs catalyst. By adjusting the reaction time, catalyst amount, and composition of the initial system, we obtain a set of statistical multiblock copolymers that differ in the composition and average length of norbornene and dodecenylene unit sequences. Structural, thermal, and mechanical characterization of the copolymers with NMR, XRD, DSC (including thermal fractionation by successive self-nucleation and annealing), and rotational rheology allows us to relate the reaction conditions to the average length of crystallizable unit sequences, thicknesses of corresponding lamellas, and temperatures of their melting. We demonstrate that isolated dodecenylene units can be incorporated into crystalline lamellas so that even nearly random copolymers should retain crystallinity. Weak high-temperature endotherms observed in the multiblock copolymers of norbornene with cyclododecene and other cycloolefins could indicate that the corresponding systems are microphase-separated in the melt state.

Replacing the aqueous coagulation bath with an alcoholic one during spinning cellulose fibers (films) from solutions in N-methylmorpholine-N-oxide leads to a radical restructuring of the hydrogen bonds net of cellulose and, as a result, to a change in the structure and properties of the resulting material. By the method of optical interferometry, it was possible to identify the intrinsic features of the interaction of the solvent and isomeric alcohols and to construct phase diagrams of binary systems describing the crystalline equilibrium. Knowledge of the phase states of the system at different temperatures renders it possible to exclude the process of solvent crystallization and conduct the spinning in pseudo-homogeneous conditions. The structure and morphology of samples were studied using X-ray diffraction and scanning electron microscopy methods for a specific coagulant. When the solution under certain conditions is coagulated at contact with alcohol, the solvent may be in a glassy state, whereas, when at coagulation in water, an amorphous-crystalline structure is formed. The structural features of cellulose films obtained by coagulation of solutions with water and alcohols help to select potential engineering or functional materials (textile, packaging, membranes, etc.), in which their qualities will manifest to the best extent.

Measurements of the photoluminescent spectra and kinetics, and of the excitation spectra of photoluminescence of CdSe nanoparticles embedded in various polymer matrices, show that using a liquid crystalline polymer as a matrix makes it possible to increase the lifetime of photoluminescence and the quantum yield of this process.

An effect of several polymeric stabilizers on the composites based on a diblock copolymer of styrene and 2-vinyl pyridine and spherical Au nanoparticles has been studied. Among the tested substances were thiol-terminated polystyrene, thiol-terminated poly(2-vinyl pyridine), diblock copolymers of styrene with 2- and 4-vinyl pyridine, and decanethiol as a typical low molecular mass stabilizer. Thin composite films with a microphase-separated cylindrical morphology have been prepared and characterized by atomic force and scanning electron microscopy to describe the surface morphology and nanoparticle distribution in the block copolymer matrix. In all the cases, the nanoparticles were selectively positioned either within vinyl pyridine domains or at the domain boundaries. The most effective stabilization of Au nanoparticles, both regarding their location and prevention of aggregation, was provided by the diblock copolymers.

An original optical method and differential scanning calorimetry were used to construct an experimental phase diagram for the binary composition low-density polyethylene – highly refined mineral oil. This diagram includes the polymer full amorphization curve and the oil solubility curve that describes the osmotic equilibrium between the swollen polymer and pure mineral oil. Within the domain between these curves, the system can be identified with a single-phase microheterogeneous gel with polymer crystallites as physical crosslinks. Two critical compositions containing 17 and 36 wt% of polyethylene were found. The first one corresponds to the least amount of polymer needed to form a capillary-porous body upon cooling down the pre-homogenized mixture. The second composition contains the fraction of oil above which the polymer full amorphization temperature is no longer decreased. Comparing with the optical method, calorimetry is much faster and able to catch weak mineral oil crystallinity, but less accurate and unable to supply any data for the solubility curve. An empirical analysis of the parameters describing the polymer full amorphization curve allowed us to conclude that mineral oil is less miscible with low-density polyethylene than decane and tridecane. The results obtained can be useful for the optimization of the properties of rubber-based vibration-damping compositions filled with polyethylene and mineral oil.

An exchange reaction of cross-metathesis between polynorbornene and poly(5-hydroxyoctenamer) in a chloroform–methanol mixture (10: 1 vol/vol) in the presence of Ru–carbene Grubbs’ complexes Gr-1 and Gr-2 has been studied. Gr-2 catalyst has a much higher activity and allows one to obtain multiblock copolymers, which cannot be synthesized directly from norbornene and 5-hydroxy-1-cyclooctene. The average length of the copolymer blocks varies in a wide range depending on the reaction conditions. The individual stages of the process have been studied with the use of in situ monitoring of transformations of Ru–carbene complexes by 1Н NMR spectroscopy and ex situ analysis of heterodyad evolution in copolymers via 13C NMR spectroscopy. As has been shown, poly(5-hydroxyoctenamer) forms Ru–carbene complexes with the catalyst more easily than polynorbornene; in this case, the incorporation of a substituent in the monomer unit of octenamer retards the polymer cross-metathesis. It has been found that, in systems containing Gr-2 and hydroxyoctenamer blocks, the formed ruthenium hydride complexes initiated hydrogenation process. The hydrogenation results in the appearance of crystallinity in the initially amorphous polymers, which opens up the possibilities for the targeted control of the multiblock copolymers properties.

The epoxidation of double bonds in random multiblock copolymers of norbornene and cyclooctene is studied for the first time. The initial copolymers with different composition and average block length are synthesized via the cross-metathesis reaction between polynorbornene and polycyclooctene in the presence of the first-generation Grubbs catalyst. New multiblock copolymers containing oxirane fragments in the backbone are obtained with a yield of 85–92% through epoxidation conducted under the action of m-chloroperbenzoic acid in toluene. The kinetics of epoxidation of polynorbornene, polycyclooctene, and their multiblock copolymers in deuterochloroform and deuterobenzene is investigated via the in situ monitoring of transformation of double bonds using 1Н NMR spectroscopy. It is shown that on the whole the modification of cyclooctene units occurs more easily in copolymers than that in the homopolymer. The thermal properties of epoxidized homo- and copolymers are examined. It is found that upon epoxidation the glass-transition temperature and the melting temperature of multiblock copolymers increase by 40–50 and 20–30°С, respectively, wherein the degree of crystallinity and the temperature of melting grow with the length of the cyclooctene block.

Novel membrane materials—three-dimensional polydimethylsiloxane networks with nonaggregated metal atoms (Fe, Zr)—have been synthesized using commercial siloxane rubber SKTN and polyfunctional metallosiloxane as a crosslinking agent. For the resulting composites, the permeability, diffusion, and solubility coefficients for a wide range of gases have been determined. It has been found that the permeability coefficients for most of the gases are close to values previously obtained for linear siloxanes; however, the permeability and Р(С4Н10)/Р(СН4) selectivity for n-butane are significantly higher. It has been shown that the differences in the permeability coefficients are attributed to higher solubility coefficients of gases in the synthesized composites.

A fast route to transfer Au nanoparticles from aqueous to organic media is proposed based on the use of a high molecular mass diblock copolymer of styrene and 2-vinylpyridine for ligand exchange at the nanoparticle surface. The method enables the preparation of stable sols of Au nanorods with sizes of up to tens of nanometers or Au nanospheres in various organic solvents. By comparing the optical absorbance spectra of Au hydro- and organosols with the data of numerical simulations of the surface plasmon resonance, we find that nanoparticles do not aggregate and confirm the transmission electron microscopy data regarding their shape and size. The proposed approach can be effective in preparing hybrid composites without the use of strong thiol and amine surfactants.

The paper describes the synthesis and physical-chemical properties of anisotropic derivatives of (-)-L-lactic acid and their nanocomposites. Anisotropic optically active aryl (S)-2-(ω-halogenalkoxy...

The work is devoted to exploring the possibility of using supercritical fluids as media for modification of polymers offering promise for production of gas-separation membranes with the goal to improve selectivity towards CO2. The possibility is demonstrated for introduction of fragments of quaternary ammonium salts into the structure of poly(4-methyl-2-pentyne) with the help of a two-stage process: bromination of the initial polymer with N-bromosuccinimide followed by the addition of the tertiary amine—N-butylimidazol— conducted in supercritical fluids as a medium. The use of trifluoromethane as the reaction medium provides the highest degree of modification of the brominated polymer with the amine. The polymer produced under the optimized conditions demonstrates a threefold increase of the calculated selectivity of separation of CO2 and N2 in comparison with the initial poly(4-methyl-2-pentyne).

The cross-metathesis reaction between polytrimethylsilylnorbornene and polycyclooctene is investigated for the first time. Using the Grubbs Ru-carbene complex of the first generation, the synthesis of random multiblock copolymers of trimethylsilylnorbornene and cyclooctene is carried out. The effect of the reaction conditions on the block length and thermal and crystalline properties of new copolymers is studied by NMR, GPC, and DSC methods. With the use of in situ 1Н NMR spectroscopy, the kinetics of the crossmetathesis reaction is investigated. As for unsubstituted polynorbornene (Polym. Sci., Ser. B 58, 292 (2016)), the catalyst interacts initially with polycyclooctene, giving a polymer carbene complex [Ru]=PCO. Further, this complex attacks the polytrimethylsilylnorbornene chain via cross reaction with formation of complex [Ru]=PNB-Si and a diblock copolymer of trimethylsilylnorbornene and cyclooctene as reaction products. The subsequent cross reactions form a multiblock copolymer with gradually increasing block length. Throughout the entire process, the concentration of [Ru]=PCO exceeds the concentration of [Ru]=PNB-Si by more than two orders of magnitude. Simultaneously, the total concentration of carbene complexes decreases in time through their decay. The reaction kinetics is satisfactorily described by a model proposed previously for interaction between polycyclooctene and polynorbornene.

We report on effects of the matrix on photoluminescence spectra and lifetime and efficiency of up-conversion of core-type CdSe and core/shell CdSe/ZnS quantum dots embedded into smectic and amorphous polymers.

Studies of thermodynamics of the N*-I phase transitions and optical properties of the new liquid crystal - (R)-2-[4″-(trans-4-butylcyclohexyl)-2′-chloro-p-terphenyl-4-oxy] propanoic acid are carried out. The aim of these studies is to analyze the capabilities of that liquid crystal to simultaneously serve as a matrix for inorganic semiconductor nanoparticles (NP) as well as a chiral dopant for liquid crystals and a chiral ligand stabilizing the surface of CdSe NPs. The chiral doping of a nematic liquid crystal was proven by the measurements of selective transmittance of the visible light. The embedding of NPs in a nematic liquid crystal leads to the increase in TN⁎I, which is explained by the shape anisotropy of the NPs. The anisotropy of the ligand shell may result from the interaction between the ligand and LC matrix inducing the change of the spherical shape of the shell toward the ellipsoidal one. TN⁎I of the liquid crystal matrix of (R)-2-[4″-(trans-4-butylcyclohexyl)-2′-chloro-p-terphenyl-4-oxy] propanoic acid (R-MPA) decreases with the embedding of NPs stabilized by the same ligands, which is in a good agreement with prior experimental results and theory, but there exists a considerable quantitative difference.

Crystallinity of statistical multiblock copolymers of norbornene and cyclooctene with nearly equimolar composition and different degrees of blockiness is studied by differential scanning calorimetry including thermal fractionation by successive self-nucleation and annealing and by X-ray diffraction. The copolymers are synthesized via recently invented reaction of polymer cross-metathesis, as a result of interchain exchange between polynorbornene and polyoctenamer in the presence of Grubbs’ catalyst of the first generation. This catalyst raises the fraction of trans-octenylene units up to more than 80% promoting formation of triclinic crystals. The copolymer degree of crystallinity and melting peak temperature decrease with the cross-metathesis conversion. At the same time the equilibrium melting temperature predicted by the Flory theory of copolymer crystallization is not much affected by the interchange reaction. Compared with the pure polyoctenamer or its equimolar blend with polynorbornene, the norborene-cyclooctene copolymers form considerably smaller crystallites. Thermal fractionation makes it possible to find their size distribution, which correlates with the average length of trans-octenylene blocks. Short annealing the multiblock copolymers above their melting points gives rise to a small but persistent endotherm 5–10 degrees above the annealing temperature, which is absent in polyoctenamer and, therefore, may indicate mixing of segregated norbornene and cyclooctene blocks.

The state diagram of the low-density polyethylene–p-xylene system that contains the solubility curve of p-xylene in the polymer is first built using the optical method with the involvement of the DSC data. It has been shown that, at 72°C, in a blend with a polymer mass fraction of 0.28, the full amorphization of the polymer proceeds simultaneously with the dissolution of p-xylene in it. Blends with a lower polymer content are also homogenized at the same temperature, although the duration of this process can take several days. In blends with a high polymer content, homogenization occurs at a higher temperature. This process is preceded by the formation of microheterogeneous single-phase gel with network junctions as polymer crystallites and amorphous regions saturated by p-xylene. Cooling of the homogeneous blends to–20°С is not accompanied by the full separation of low- and high-molecular-mass phases; in this case p-xylene not only forms an individual crystalline phase, but also partially crystallizes in amorphous regions of the polymer.

A method of controlled radical polymerization via the reversible addition fragmentation chain transfer mechanism is used to synthesize LC polymers with functional terminal thiol groups. These polymers are used to create composites containing gold nanoparticles at a concentration of up to 40 wt % and capable of LC ordering. The structural, thermodynamic, and optical properties of the composites are studied. It is shown that the spatial separation of mesogenic groups and groups responsible for the binding of a macromolecule with nanoparticles makes it possible to considerably widen the concentration range of nanoparticles while preserving the LC state of the composites.

A procedure of selective bromination of poly(1-trimethylsilyl-1-propyne) using N-bromosuccinimide as the brominating agent was developed. This method allows to obtain samples with different bromine content depending on the process conditions. The obtained brominecontaining polymers have good film-forming properties, satisfactory thermal and thermo-oxidative stability. The introduction of bromine atoms into the polymer increases the stability of the latter to aliphatic hydrocarbons C5—C12 and improves hydrophobicity. With an increase of bromine content in the polymer, the selectivity of separation of gas pairs CO2/N2, CO2/H2, and O2/N2 increases, while the level of permeability remains high.

Cross-metathesis of 5-hydroxycyclooctene and norbornene homopolymers affords the multiblock copolymer possessing a broad range in the degree of blockiness (from 0.03 to 1).

The phase behavior of low-density polyethylene mixtures with 1,2,4,5 – tetrachlorobenzene and camphor is investigated by optical methods and differential scanning calorimetry. The use of a photoconductive cell integrated into an optical microscope equipped with a heating stage, allows us, for the first time, to combine turbidimetry with visual observations to detect crystallization of a low-molar-mass substance from the amorphous regions of a semicrystalline polymer. Crystallization in the restrained conditions of an apparently solid polymer matrix leads to crystals much smaller than the low-molar-mass crystals formed in a mixture with the melted polymer. We discuss the details of reversible structural changes taking place to the binary mixtures of crystallizable components in the course of their heating and cooling. Constructed phase diagrams provide important information for developing technologies based on thermally induced phase separation in such systems.

This research examines the possibilities of regulating the structure of cellulose precursor fibers spun from solutions in N-methylmorpholine-N-oxide when replacing aqueous coagulation baths with thermodynamically softer alcohol baths at different temperatures. The fibers were spun by the dry jet&ndash, wet method in isobutanol coagulation baths with a temperature of 25 &deg, C and 70 &deg, C. The study of the phase state of the solvent&ndash, coagulant system using viscometry and point cloud methods revealed the temperature-concentration regions of the single-phase and two-phase states of the system. Using elemental analysis, DSC (differential scanning calorimetry) and XRD (X-ray diffraction) methods, it was shown that just spun fibers, due to the presence of a residual amount of solvent and coagulant in them, regardless of the temperature of the precipitator, have an amorphous structure. Additional washing with water completely washed away the solvent and coagulant as well, however, the structure of cellulose changes slightly, turning into a defective amorphous-crystalline one. A relationship was found between the phase composition, structure, and properties of just spun fibers and precursors washed with water. Thus, the loss of structural ordering of both just spun and washed cellulose fibers leads to a decrease in strength characteristics and an increase in deformation. The thermal behavior of the fibers is determined by their phase composition. Fibers just spun into hot alcohol containing a coagulant and traces of solvent acquire thermal stability up to 330 &deg, C. During the pyrolysis of the obtained precursors up to 1000 &deg, C, the value of the carbon yield doubles. The amorphized structure of the obtained fibers allows us to consider it as a model when analyzing the transformation of the structure of precursors during thermolysis.

Polystyrene (PS) containing a terminal thiol group has been synthesized to create composites with CdSe and CdSe/ZnS quantum dots (QDs). Reversible addition fragmentation chain transfer (RAFT) polymerization carried out using asymmetric agent enables a facile synthesis of monochelic macromolecules with functional terminal groups. Modification of the terminal groups does not practically change the polymer molecular weight and the narrow molecular weight distribution. The interaction of the thiol group with the QD surface results in the partial substitution of low molecular weight ligands by macromolecules. The process of the formation of polymer – QD complex in the sol was studied by means of static and dynamic light scattering. The size and morphology of polymer – QD complex in the sol is compared with those in the solid films. Several possible models of the packing of polymer – QD complex are discussed.

A new type of phase diagram semicrystalline polymer – low molecular mass substance is found for the low-density polyethylene – dimethyl terephthalate mixture. Exploiting an original optical method and differential scanning calorimetry, we demonstrate that the studied system combines the features of polymer – poor solvent and polymer – high-melting substance mixtures. Its diagram also contains a curve describing the solubility of the low molecular mass component in the polymer, which is often missing in the literature. An experimental phase diagram enables us to perform a detailed analysis of the differential scanning calorimetry, optical and scanning electron microscopy data on the cooling of homogenized mixtures of different compositions, which leads to the formation of capillary-porous polyethylene bodies via thermally induced phase separation and following removal of dimethyl terephthalate crystals.

Composites based on microphase-separated diblock copolymers of styrene with vinylpyridine and gold nanoparticles, in which the block copolymers play simultaneously both the role of a stabilizer preventing the aggregation of nanoparticles and a matrix providing their selective arrangement within domains of the predefined type, are obtained for the first time. The suggested approach implies no use of additional stabilizers and is efficient for both initially organic dispersed small (~5 nm) spheres and hydrasols of larger (9 × 30 nm) rodlike nanoparticles. Nanospheres are introduced into the composites via replacement of a labile stabilizer used in synthesis with the diblock copolymer, while nanorods synthesized in aqueous media by the two-stage method are incorporated via phase transfer mediated by the diblock copolymer. Films capable of microphase separation leading to the formation of vinylpyridine cylindrical domains with a diameter of tens nanometers are spin-coated from the obtained composites. The content of nanoparticles in the composites is up to 5 wt %; they are dispersed and arranged predominantly within vinylpyridine domains, with nanospheres being localized near domain boundaries, while nanorods being mainly oriented perpendicularly to the axis of cylinders.

Copolymers of norbornene and cyclooctene were synthesized for the first time by the cross-metathesis of polynorbornene with polyoctenamer. This strategy made it possible to use the 1st generation Grubbs catalyst, which exhibits low activity toward copolymerization of those monomers. Statistical multiblock copolymers with average block lengths varying from 200 to 2 units were obtained.

The role of specific interactions between a polymer matrix and incorporated quantum dots is one of the critical problems for understanding the effect of the polymer matrix on the optical properties of quantum dots in a nanocomposite material and for creating new photonic materials and related instruments. In this study, cadmium selenide quantum dots have been incorporated into a liquid-crystalline polymer via the interaction of carboxyl groups of the polymer with the quantum-dot surfaces through ionic bonds. From the data of transmission electron microscopy, it has been shown that this interaction provides the localization of quantum dots in the environment of the liquid-crystalline phase of the polymer. Various features of photoluminescent properties have been observed and interpreted in terms of the emission recombination of excitons in CdSe quantum dots, light reabsorption by quantum dots, the effect of the electronic states on the surface CdSe-liquid crystal, and the energy transfer from quantum dots to the polymer liquid-crystalline matrix.

Bulk and solution studies revealed a strongly pronounced effect of chain structure on the rheological and relaxation behavior of well-characterized vinyl acetate–vinyl alcohol copolymers of similar composition and polymerization degree. The frequency–temperature superposition principle is fully applicable to the random copolymers, which demonstrate all expected relaxation states, whereas a divergence of the reduced dynamic moduli–frequency dependences is observed for the multiblock copolymers. In the latter case, the terminal zone is sensitive to the self-assembling of vinyl alcohol blocks into (depending on the copolymer composition) crystalline or amorphous microstructures. The monomer unit distribution particularly affects properties of the copolymer solutions in N,N-dimethylformamide (DMF). 5% solutions behave as simple viscoelastic liquids at 20 °C and show viscoplastic behavior at −20 °C, where more blocky chains are characterized by up to 4 orders of magnitude higher yield stress values. The multib...

On the basis of copolymers of 4-methoxyphenyl-4-(6-(acryloyloxyhexyloxy)benzoate with 4-(6-acryloyloxyhexyloxy)benzoic acid, nonequilibrium composites containing nanoparticles (quantum dots) of cadmium selenide at concentrations many times higher than their solubility limit in the liquid-crystalline phase are synthesized. In the resulting material, the polymer matrix undergoes the transition to the liquidcrystalline state before separation into phases with concentrations of nanoparticles corresponding to thermodynamically equilibrium values. Under common conditions, the composites are stable for at least several months.

A comparative study of the viscoelastic properties of melts of vinyl acetate-vinyl alcohol copolymers with equimolar compositions characterized by different statistical distributions of chain units has been performed. It has been shown that the principle of temperature-frequency superposition is obeyed by copolymers close to a random copolymer, but is violated by copolymers with the block distribution of units. Unlike amorphous random copolymers, a multiblock copolymer is characterized by weak crystallinity, the absence of the relaxation flow state, and a more pronounced tendency to form interchain hydrogen bonds both between two hydroxyl groups and between hydroxyl and ester groups.

By means of in situ melt polycondensation of polyethylenterephathalate accompanied with simultaneous reduction of introduced graphene oxide, the composite of polyethylenterephathalate filled with reduced graphene oxide was prepared. Melting and crystallization of the reduced graphene oxide – polyethyleneterephthalate composite was studied by the differential scanning calorimetry method, and the rheological test was carried out by rotational rheometry and compared to the pristine polyethylenterephathalate. The morphology of the reduced graphene oxide – polyethyleneterephthalate composite was studied using optical microscopy. The reduced graphene oxide was isolated from the reduced graphene oxide – polyethyleneterephthalate composite and characterized by thermogravimetry, X-ray photoelectron spectroscopy and X-Ray diffraction methods. Since a part of polymer could not be removed from reduced graphene oxide particles by trifluoroacetic acid, the hypothesis about probable grafting of polyethyleneterephthalate on reduced graphene oxide sheets was suggested. Rheological behaviour of the reduced graphene oxide – polyethyleneterephthalate composite melt confirms this suggestion. According to the calculations based on thermogravimetry, the reduced graphene oxide, isolated from the reduced graphene oxide – polyethyleneterephthalate composite, consists of about 80% polyethyleneterephthalate.

The effect of solvent on the photoluminescence of cadmium selenide quantum dots stabilized by oleic acid is examined with the example of two organic solvents: toluene and THF. It is found that THF favors desorption of ligands and formation of surface defects to a greater extent than toluene; as a result, the maximum of the photoluminescence band shifts to the red spectral region and its intensity decreases. The addition of polymers to the solution of quantum dots causes changes in the efficiency of photoluminescence and in the kinetics of its quenching. In the range of low concentrations (≤2 wt %) of quantum dots in polymer solutions, the intensity of luminescence first grows and then passes through a maximum and decreases. This effect may be explained both by the increasing number of surface defects and by quenching via energy transfer to polymers, especially in the case of polymers containing aromatic groups.

The phase state of polyelectrolyte blends based on acrylic copolymers was investigated with differential scanning calorimetry, transmission electron microscopy (TEM), and wedge microinterferometry as a function of the blend composition and ionization of polymer functional groups. A copolymer of N,N-dimethylaminoethyl methacrylate with methyl methacrylate and butyl methacrylate was used as a polybase, a copolymer of methacrylic acid and ethyl acrylate was employed as a polyacid, and the optional plasticizer was triethyl citrate. A correlation was established between an earlier described mechanism of molecular interaction and the behavior of the glass-transition temperature (Tg) of the polymer blends. The Tg values of the polyelectrolyte complexes in the gel phase were always higher than Tg in the sol phase. This fact implies that intermolecular cohesion dominated the free volume in the stoichiometric polyelectrolyte complexes formed in the gel phase, whereas nonstoichiometric complexes formed in the sol phase were characterized with the predominant contribution of free volume. TEM and interferograms of polyelectrolyte blends showed the signs of anisotropic ordered supramolecular structure formation. A phase-state diagram of the polyelectrolyte blends was constructed. The stoichiometric polyelectrolyte complex was immiscible with parent polymers, forming a separate phase that became melted at elevation of temperature because of complex dissociation. Polyelectrolyte miscibility was supposed to result rather from the chemical reaction of the complex formation than from interdiffusion of the polymer components along the gradient of their concentration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011