Thermoresponsive PEG‐based (PEG stands polyethylene glycol) polymers are unique for use in medicine because of their low toxicity, good biocompatibility and biodegradability, but usually more ...hydrophobic and more toxic comonomers are used to adjust lower critical solution temperature (LCST). A convenient way to overcome this problem and to finely tune LCST is to use alkoxy oligo(ethylene glycol)‐ or alkoxy oligo(propylene glycol) (meth)acrylates as starting comonomers. Here we report on the conditions for the simple and affordable synthesis of methoxy oligo(propylene glycol) (meth)acrylate‐ and methoxy oligo(propylene glycol)‐block‐oligo(ethylene glycol) (meth)acrylate‐based macromonomers with high yields (80%–98.7%) by the acid‐catalyzed esterification of (meth)acrylic acid with alkoxy oligo(alkylene glycols) containing oligo(ethylene glycol) (OEG) and/or oligo(propylene glycol) (OPG) blocks. p‐Toluene sulphonic acid (pTSA), alkyl(C12–C14)benzene sulfonic acid (ABSA) and H2SO4 were used as catalysts. It has been shown that pTSA and ABSA are practically the same in catalytic activity and are superior to sulfuric acid. The reaction orders with respect to catalyst was found to be close to 1 in all cases. It has been shown that the reaction is actually insensitive to the lengths of OEG and OPG blocks, as well as to the structure of the terminal alkyl group, while the esterification of acrylic acid (AA) proceeds much faster compared to methacrylic acid (MAA) one under the same conditions. The influence of temperature on the equilibrium conversions of alcohols was determined, which were found to be 89%–93% for the esterification of AA and 61%–86% for MAA in the temperature range of 60–120°C. A further increase in conversion was achieved by introducing an azeotropic agent (toluene), its optimal concentration was found to be 10%–15%.
This paper aims to consider approximation-estimation tests for decision-making by machine-learning methods, and integral-estimation tests are defined, which is a generalization for the continuous ...case. Approximation-estimation tests are measurable sampling functions (statistics) that estimate the approximation error of monotonically increasing number sequences in different classes of functions. These tests make it possible to determine the Markov moments of a qualitative change in the increase in such sequences, from linear to nonlinear type. If these sequences are trajectories of discrete quasi-deterministic random processes, then moments of change in the nature of their growth and qualitative change in the process match up. For example, in cluster analysis, approximation-estimation tests are a formal generalization of the “elbow method” heuristic. In solid mechanics, they can be used to determine the proportionality limit for the stress strain curve (boundaries of application of Hooke’s law). In molecular biology methods, approximation-estimation tests make it possible to determine the beginning of the exponential phase and the transition to the plateau phase for the curves of fluorescence accumulation of the real-time polymerase chain reaction, etc.
The synthesis and solution properties of thermoresponsive polymer molecular brushes based on five novel diblock macromonomers (methoxy oligo(ethylene glycol)
e
-
block
-oligo(propylene glycol)
p
...methacrylates, OEG
e
OPG
p
MA, where
e
= 7.0–10.3 and
p
= 2.8–10.3) have been studied. The effect of synthesis conditions on the rate of radical solution polymerization in ethyl acetate, maximum conversions of macromonomers, and molecular weight characteristics of polymers has been shown. Homopolymers of OEG
e
OPG
p
MA exhibited pronounced surface-active properties. The influence of the length of oligo(propylene glycol) block on the degree of reduction of surface (air–water) and interfacial (hexane-water) tension was shown. The aggregation behavior of polymers was investigated by dynamic light scattering and fluorimetry using pyrene as a fluorescent probe. The dependence of critical micelle concentration on the length of the oligo(propylene glycol) block was shown. The polymers have a critical solution temperature within the range of 34–71 °C depending on the length of oligo(oxyalkylene) blocks and polymer concentration. The relationship between the distribution coefficient of macromonomers in water–oil systems and the LCST of polymers based on them has been established.
A new technique of detection of dark photons as cold dark matter by means of a multicathode counter is described. The first results obtained with the aid of this technique are presented. Also, its ...potential for providing evidence on the basis of searches for symmetry in the time distribution of diurnal variations because of the rotation of the Earth in the stellar reference frame for the rate of counting of single electrons emitted from the metallic cathode of the counter via the conversion of dark photons is discussed.
Amphiphilic sulfo- or amino-containing molecular brushes are synthesized by the radical copolymerization of methacrylic esters containing oligo(ethylene glycol) and/or oligo(propylene glycol) blocks ...of varying length and arrangement with 2-acrylamido-2-methylpropanesulfonic acid or
N
-(3-dimethylaminopropyl)methacrylamide in solutions (water, ethyl acetate, toluene). In copolymerization with 2-acrylamido-2-methylpropanesulfonic acid in water, the compositional homogeneity of the copolymers grows appreciably with increasing concentration of initial solutions. It is shown that the structure of macromonomers has almost no effect on their reactivity ratios in copolymerization with
N
-(3-dimethylaminopropyl)methacrylamide in organic solvents. The synthesized amino-containing molecular brushes exhibit stimuli-responsive properties in aqueous solutions, and the arrangement of hydrophilic and hydrophobic blocks in the side chains of macromolecules affects dependences of the phase transition temperature on polymer concentration and рН.
Phosphate ore are a complex combination of chemical substances in natural minerals. The complicated physicochemical process of heating phosphorites includes a set of heat and mass exchange processes, ...endothermic reactions of carbonates dissociation, and processes of structural transformations during solid- and liquid-state sintering. The temperature-concentration and temperature-time dependences of the heat capacity of phosphate ore samples on the thermal conditions of the carbonates dissociation reaction in the samples, under structural modifications, as a result of a change in the chemical composition of the samples were experimentally investigated. The influence of the structural changes in the samples in the range of the raw material roasting temperatures and of the heating rates on the heat capacity of the phosphorites was evaluated. Scientific justification was provided for the occurrence of significant temperature gradients in the samples due to transient heating conditions and to the action of the thermal effects of the carbonates dissociation reaction, which limits the applicability of conventional methods to determine the true and effective heat capacities of the samples. The relationship between the heterogeneous endothermic structural transformations and the thermophysical conditions of the endothermic reaction of carbonates dissociation was established, which allows increasing the energy efficiency of the thermal treatment of the phosphate raw material during beneficiation on roasting conveyor and sintering machines. Analysis of the experimental data reveals a significant effect of thermal dissociation of carbonates and of the internal heat exchange on the heat capacity of the phosphorites. The error of the found heat capacity is determined by the technique of thermoanalytical experiments, the dimensions of the samples, the thermal effect of the carbonates dissociation reaction, and the reacting phase concentration. The error increases with an increase in the sample heating rate, i.e., with growth of the factors increasing the steepness of the temperature gradient field in the samples. The chemical and energy technological features of the thermal treatment of the phosphate raw materials are determined by the dependence of their heat capacity on the endothermic reaction of carbonates dissociation during heating in a wide range of heating rates in a moving dense multilayer of pellets on the grate of operating roasting conveyor machines, which allows optimizing energy-saving roasting modes.
The article is concerned with the conceptual modeling of multifunctional hydrofoil vessel "Afalina". The review of analogs is represented and the basic characteristics of this type of vessels as well ...as their multitasking functionality are described. The search of lines is carried out on the basis of biological prototypes and the searching process is illustrated by the variants of rough drawings. The vessel drawings are designed on the basis of chosen rough drawing; the constructional features and ergonomics of different modifications are described. The methods and tools of three-dimensional computer modeling are selected; shading and rendering stages are represented. The settings of multifunctional hydrofoil vessel rendering are obtained in the course of engineering.
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