RHEOKINETIC AND MORPHOLOGICAL FEATURES OF THE REACTION FORMATION OF A POLYMER COMPOSITE MATERIAL BASED ON IMPACT-RESISTANT POLY(METHYL METHACRYLATE). MODEL AND APPLIED ASPECTS

Based on the experimental data on the rheology of dispersions of hydrophobic aerosil (Am) in a low molecular weight hydrocarbon medium, the possibility of using a «micellar» mechanism for the formation of a bulk structure for such dispersions is considered. A model of such a structure before, during and after shear deformation is proposed, which makes it possible to interpret experimental data on the rheology of dispersed systems. The results of the study of rheokinetics are presented in a new visio – from the point of view of self-organization under the influence of the shear field. The PMMA–PU–Am system was considered as a polymer composite (PC), in which the matrix is the poly(methyl methacrylate) (PMMA) being modified, and the dispersed phase is a mixture of polyurethane (PU) with Am. It has been shown that during the reaction formation of this composition, the conditions of shear deformation of the system correspond to those at which self-organization and fixation of the coagulation rheopex structure of the nanofiller in PC is possible at the moment of reaching very high viscosity values (gel-point), when diffusion processes will be practically frozen. Two concentration regions of Am were predicted (before and after the percolation threshold), where an enhancement of the mechanical characteristics of PMMA can be expected. The relationship between the rheokinetics of the formation of a linear PMMA–crosslinked PU mixture in the presence of different amounts of oligomeric azo-initiator containing fragments of the polyurethane chain and groups capable of initiating radical polymerization of methyl methacrylate and the process of phase separation, morphology and mechanical properties of the final products has been established. It was shown that the time of phase separation and gelation are interrelated and there is in a simple dependence on the concentration of the azo-initiator. Such an initiator affects the structural-rheological transitions in the system and leads to the formation of morphology with smaller domains. The most stable system with the best dispersion of polyurethane in polymethyl methacrylate is a mixture containing 0.002 mol/L of azo-initiator, which has improved mechanical properties and increased impact viscosity.

Mitochondria-targeted accumulation of oxygen-irrelevant free radicals for enhanced synergistic low-temperature photothermal and thermodynamic therapy

Background Although lower temperature (< 45 °C) photothermal therapy (LPTT) have attracted enormous attention in cancer therapy, the therapeutic effect is still unsatisfying when applying LPTT alone. Therefore, combining with other therapies is urgently needed to improve the therapeutic effect of LPTT. Recently reported oxygen-irrelevant free radicals based thermodynamic therapy (TDT) exhibit promising potential for hypoxic tumor treatment. However, overexpression of glutathione (GSH) in cancer cells would potently scavenge the free radicals before their arrival to the specific site and dramatically diminish the therapeutic efficacy. Methods and results In this work, a core–shell nanoplatform with an appropriate size composed of arginine–glycine–aspartate (RGD) functioned polydopamine (PDA) as a shell and a triphenylphosphonium (TPP) modified hollow mesoporous manganese dioxide (H-mMnO2) as a core was designed and fabricated for the first time. This nanostructure endows a size-controllable hollow cavity mMnO2 and thickness-tunable PDA layers, which effectively prevented the pre-matured release of encapsulated azo initiator 2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride (AIBI) and revealed pH/NIR dual-responsive release performance. With the mitochondria-targeting ability of TPP, the smart nanocomposites (AIBI@H-mMnO2-TPP@PDA-RGD, AHTPR) could efficiently induce mitochondrial associated apoptosis in cancer cells at relatively low temperatures (< 45 °C) via selectively releasing oxygen-irrelevant free radicals in mitochondria and facilitating the depletion of intracellular GSH, exhibiting the advantages of mitochondria-targeted LPTT/TDT. More importantly, remarkable inhibition of tumor growth was observed in a subcutaneous xenograft model of osteosarcoma (OS) with negligible side effects. Conclusions The synergistic therapy efficacy was confirmed by effectively inducing cancer cell death in vitro and completely eradicating the tumors in vivo. Additionally, the excellent biosafety and biocompatibility of the nanoplatforms were confirmed both in vitro and in vivo. Taken together, the current study provides a novel paradigm toward oxygen-independent free-radical-based cancer therapy, especially for the treatment of hypoxic solid tumors. Graphical Abstract

SILICON-CONTAINING OLIGOMERIC AZOINITIATORS IN THE SYNTHESIS OF BLOCK COPOLYMERS

The aim of the work was to develop methods for the synthesis and study of the properties of silicon-containing oligomeric azo- and polyazoinitiators based on bis-γ-hydroxypropylpolysiloxane (HPS) and bis-γ-aminopropylpolysiloxane (APS). Silicon-containing oligomeric azoinitiators using HPS were synthesized on the basis of cyclohexanone azo-bis-isobutyrohydrazone (AGN-CH) and bis-γ-hydroxypropylpolysiloxane bifunctional macrodiisocyanate (MDIHPS). MDIHPS was obtained by the interaction of GPS with 2,4 toluene diisocyanate (2,4-TDI). Oligomeric azoinitiators have been obtained, which have the structure RXR and (RX)nR, where R is a propylpolysiloxane block, X is a azo initiator block. For the synthesis of an oligomeric azo initiator based on bis-γ-aminopropyl polysiloxane (APS), a method was first developed for the synthesis of a monomeric azo initiator with terminal oxadiazolinylcarbamanate isocyanate groups (AGN-NCO) by the interaction of AGN-CH and 2,4-TDI at a molar ratio of 1: 2. On the basis of the obtained AGN-NCO and APS at a molar ratio of AGN-NCO: APS = 1: 1, an oligomeric azo initiator (OAI APS-P) was synthesized, which has the structure (RX)nR, where R is a propylpolysiloxane block, X is an azo initiator block. The structures of monomeric and oligomeric azo initiators have been studied by UV and IR spectroscopy, and the kinetic regularities of their synthesis have been calculated. On the basis of oligomeric azo initiators and styrene, block copolymers of the (AB)nA type were obtained by the method of thermal and photoinitiated radical polymerization, where A is a propylpolysiloxane block, B is an oligosyrene block with a constant value of the organosilicon block and a different size of the oligostyrene block. The structure of block copolymers was investigated by IR spectroscopy. It was shown that during photopolymerization, oligostyrene blocks of shorter length are formed than during thermopolymerization, and possible oxidation processes. The study of relaxation transitions by DSC in oligostyrene and propylpolysiloxane blocks of the BCP showed that the common heat capacity curves are the presence of two jumps in the heat capacity at the glass transition temperatures of the polysiloxane and oligostyrene microphase. A slight shift in the glass transition temperature of polysiloxane microphases in BCP towards higher temperatures compared to the homopolymer may be associated with the effect of oligostyrene microphase. With a decrease in the length of the oligosyrene block, a low-temperature shift in the glass transition temperature of oligostyrene blocks relative to the homopolymer and a depression of ∆Cp,2 are observed, which is associated with the suppression of mobility in oligodienic microphases by less mobile propylpolysiloxane blocks.

Transition Metal Salts of Carboxylated Multiwalled Carbon Nanotubes in Combination with N-hydroxyphthalimide as Catalytic Systems for Hydrocarbon Oxidation

In this study, the transition metal (Co (II), Cu (II), and Mn (II)) salts of carboxylated carbon nanotubes were synthesized and characterized (the determined metal contents were in the range of 0.89–1.16%). The catalytic activity and the possibility for recovery and reuse of the obtained heterogeneous salts were then studied in the solvent-free oxidation of ethylbenzene with oxygen. The oxidation processes were carried out at 80 °C under atmospheric pressure in the presence of N-hydroxyphthalimide. The highest conversion of ethylbenzene, 27%, was obtained with a system consisting of the Cu (II) salt of the carboxylated carbon nanotubes, N-hydroxyphthalimide, and the azo initiator AIBN.

Functionalization of the Fine Al2O3 Abrasive by the Polyacrylamide Deposition

In order to enhance the dispersion stability of ultra-fine Al2O3 powder in aqueous media, the alumina particles were modified with silane coupling agent KH570 at first, and then 2,2'-Azobis(2-amidinopropane) dihydrochloride (AIBA) was anchored onto the modified Al2O3 to initiate the graft polymerization of acrylamide monomer (AM), and PAM/Al2O3 composite particles were obtained finally. The structure and dispersion property of Al2O3 composite particles were characterized by XPS, FTIR, laser particle size analyzer, micro electrophoresis apparatus, SEM and spectrophotometer. The results indicated that the attained composite abrasive when water-soluble azo initiator was added at 40 ℃ showed good dispersion stability in aqueous media with PAM as shell and Al2O3 as core. Compared with unmodified Al2O3, the reunion phenomenon of grafting polymerization modified Al2O3 powder was improved by AM, the D50 of the modified particles reduced. The isoelectric point (IEP) of the grafting modified particles migrated, and the zeta potential of the modified particles reached to the maximum value when the pH was 9. After PAM/Al2O3 abrasive polished, the surface roughness of NiP/Al hard disk surface was obviously reduced.

Synthesis of a thermoresponsive crosslinked MEO2MA polymer coating on microclusters of iron oxide nanoparticles

Encapsulation of magnetic nanoparticles (MNPs) of iron (II, III) oxide (Fe3O4) with a thermopolymeric shell of a crosslinked poly(2-(2-methoxyethoxy)ethyl methacrylate) P(MEO2MA) is successfully developed. Magnetic aggregates of large size, around 150–200 nm are obtained during the functionalization of the iron oxide NPs with vinyl groups by using 3-butenoic acid in the presence of a water soluble azo-initiator and a surfactant, at 70 °C. These polymerizable groups provide a covalent attachment of the P(MEO2MA) shell on the surface of the MNPs while a crosslinked network is achieved by including tetraethylene glycol dimethacrylate in the precipitation polymerization synthesis. Temperature control is used to modulate the swelling-to-collapse transition volume until a maximum of around 21:1 ratio between the expanded: shrunk states (from 364 to 144 nm in diameter) between 9 and 49 °C. The hybrid Fe3O4@P(MEO2MA) microgel exhibits a lower critical solution temperature of 21.9 °C below the corresponding value for P(MEO2MA) (bulk, 26 °C). The MEO2MA coating performance in the hybrid microgel is characterized by dynamic light scattering and transmission electron microscopy. The content of preformed MNPs [up to 30.2 (wt%) vs. microgel] was established by thermogravimetric analysis while magnetic properties by vibrating sample magnetometry.

In situ small-angle X-ray scattering studies during the formation of polymer/silica nanocomposite particles in aqueous solution

SAXS is used to study the formation of polymer/silica nanocomposite particles prepared by surfactant-free aqueous emulsion polymerization of 2,2,2-trifluoroethyl methacrylate in the presence of silica nanoparticles using a azo initiator at 60 °C.

Development and Validation of Stability-Indicating HPLC Methods for the Estimation of Lomefloxacin and Balofloxacin Oxidation Process under ACVA, H2O2, or KMnO4 Treatment. Kinetic Evaluation and Identification of Degradation Products by Mass Spectrometry

The oxidation of lomefloxacin (LOM) and balofloxacin (BAL) under the influence of azo initiator of radical reactions of 4,4′-azobis(4-cyanopentanoic acid) (ACVA) and H2O2 was examined. Oxidation using H2O2 was performed at room temperature while using ACVA at temperatures: 40, 50, 60 °C. Additionally, the oxidation process of BAL under the influence of KMnO4 in an acidic medium was investigated. New stability-indicating HPLC methods were developed in order to evaluate the oxidation process. Chromatographic analysis was carried out using the Kinetex 5u XB—C18 100A column, Phenomenex (Torrance, CA, USA) (250 × 4.6 mm, 5 μm particle size, core shell type). The chromatographic separation was achieved while using isocratic elution and a mobile phase with the composition of 0.05 M phosphate buffer (pH = 3.20 adjusted with o-phosphoric acid) and acetonitrile (87:13 v/v for LOM; 80:20 v/v for BAL). The column was maintained at 30 °C. The methods were validated according to the ICH guidelines, and it was found that they met the acceptance criteria. An oxidation process followed kinetics of the second order reaction. The most probable structures of LOM and BAL degradation products formed were assigned by the UHPLC/MS/MS method.