Polymer Science, Series A最新文献

Abstract

The carbazole compound (C-C₈) containing aromatic ring with 8 carbon alkyl group (C₈) was synthesized. The thiophene-derived compound that was abbreviated as (T) was synthesized, and (CT-C₈) was obtained by adding of (T) to the starting compound (C-C₈). Additionally, the electrochemical polymers of CT-C₈ were synthesized and accumulated onto different surface types such as an indium tin oxide (ITO) coated glass, aluminum (Al) layer, copper (Cu) sheet and pen tip electrode (PTE). The electrochemical syntheses of the polymers were performed by using 0.05 M NaClO₄ as an electrolyte in acetonitrile (AN) solvent. The electrochemical behaviors of the polymers were also investigated by taking the cyclic voltammeric measurements with a triple electrode system, and the electrochemical behaviors of the coated polymers on different electrode surfaces were also researched in the presence of Fe³⁺ and Fe²⁺ metals. According to the obtained voltammogram results, it can be said that the electrochemically synthesized polymers on different electrode surfaces were sensitive to Fe³⁺ metal and they could be used as an electrochemical sensor for all electrode surfaces as mentioned above. For the performed electrochemical measurements, the oxidation and reduction peak values obtained for different electrode surfaces were different from each other. When it is desired to examine the electrochemical property of a material, there is a need to search for more useful and economical insoles, since the conductive surface like ITO is deformed after repeated applications and expensive. This study, which offers an alternative conductive base to replace ITO, is important in this regard.

Abstract

Branched polysaccharides have been isolated from basidiomycete raw materials of locally growing and cultivated Ganoderma lucidum. It has been found that the isolated fractions contain branched polysaccharides in the form of complexes with melanin. After purification of polysaccharides by ion exchange chromatography from locally growing and cultivated basidial raw materials, two fractions have been obtained: neutral polysaccharides of locally growing Ganoderma lucidum (GW-1), cultivated Ganoderma lucidum (GWL-1) with a yield of 25.71 and 29.85%, respectively, and anionic polysaccharides of locally growing Ganoderma lucidum (GW-2), cultivated Ganoderma lucidum (GWL-2), with a yield of 5.26 and 4.19%. The physicochemical properties of the obtained samples have been studied by IR and UV spectroscopies. The purity degree of fractions of branched polysaccharides has been determined. Using gas chromatography, one-dimensional (¹³C NMR, ¹H NMR), and two-dimensional (COSY, TOCSY, HSQC, HMBC, NOESY) NMR spectroscopies, the compositions and molecular structures of the obtained polysaccharide samples have been determined. The results showed that the isolated and purified polysaccharides are β-glucan-type branched polysaccharides that have branch point (1,4,6)- and (1,3,6)-linked glucopyranose residues.

Abstract

The structure and rheological properties of aqueous solutions of the anionic surfactant potassium oleate and the water-soluble monomer acrylamide before and after radical polymerization have been studied. In the absence of monomer and in the presence of a low-molecular-weight salt, potassium oleate forms a network of long entangled cylindrical (wormlike) micelles. The addition of the monomer does not lead to a change in their cylindrical shape and radius, but it promotes the transformation of branched micelles into linear ones. The structure of surfactant aggregates changes significantly after polymerization: according to neutron scattering data, it becomes bicontinuous and its local geometry becomes lamellar. The coexistence of such a structure with polyacrylamide macromolecules in a semidilute solution leads to a significant synergistic increase in viscosity and elastic modulus.

Abstract

The idea of sustainable and circular utilization of difficult to decompose plastics is pursued to add value to other products. New epoxy mortars suitable for construction repair made from epoxy oligomer, amine and modified PET waste hardeners mixed with sand were prepared. Three types of carboxyl terminated PET (CTPET) were used as co-hardeners, along with an amine, to prepare new combination linkage epoxy mortars. Investigation of the viscoelastic properties revealed that the CTPETs influenced the storage modulus at glassy state and the rubbery plateau, indicative of interfacial adhesion between the epoxy matrix and sand aggregates. Additionally, the damping behavior and glassy temperature were increased with the addition of CTPET. Moreover, the combination linkage of ester groups from the CTPET likely contribute to the enhancement of compressive strength and flexural strength in the epoxy mortar. The results of absorption and flexural change after immersion in solution, as well as the interfacial flexural bonding strength with ordinary cement-based material were also investigated.

Abstract

A series of water-soluble comb-like copolymers of N-methyl-N-vinylacetamide and N-methyl-N-vinylamine (MVAA‒со‒MVA) bearing hydrophobic dodecyl side groups С₁₂Н₂₅ has been investigated by means of molecular hydrodynamics (viscometry, translational diffusion, and analytical ultracentrifugation) in dilute solutions in 0.1 M NaCl, under conditions of suppression of the polyelectrolyte effects. The issues of homology of these amphiphilic copolymers have been considered. The viscometry data plotted as lnη_r as function of c[η] have allowed to distinguish between macromolecules of the copolymers according to their hydrophobicity. Positive values of the second derivative B₂ determined from the initial parts of these curves have served as a measure of hydrophobicity of the amphiphilic copolymers. The noticeable differences in the B₂ values for different copolymers have shown that they do not form true homologous series. For the quasi-homologous series of the MVAA–со–MVAC₁₂H₂₅·HI copolymers with close values of B₂, the Kuhn–Mark–Houwink–Sakurada relationships have been obtained and the equilibrium rigidity of the chains has been assessed using the modified Gray–Bloomfield–Hearst equation.

The influence of different types of deformation of the metal matrix on mechanical behavior of the amorphous PET film upon its transverse compression in the ductile metal matrix has been investigated. Three deformation modes have been probed. In the first case, a disc-shaped polymer specimen has been put between two 5 mm thick discs of the lead–tin alloy and squeezed in the press. In the second and the third cases, planar elongation has been performed in the so called “dead channel”, i.e., the channel with fixed side walls, the film being elongated due to decrease in the width or thickness, respectively. The plots of true yield stress at different draw ratios have formed a common master curve. At high total draw ratio Λ, the true yield stresses have been close for the considered three types of drawing in the metal. At the draw ratio Λ > 2.6, the neck has not appeared, and the specimen has been deformed uniformly. When the film in the channel is elongated due to the decrease in thickness at constant width, the specimen width has been mainly decreased during subsequent elongation in the testing machine. When the film in the channel is elongated due to the decrease in width at constant thickness, further elongation has mainly led to the decrease in the specimen thickness. The true stress Σ has been expressed as Σ = Σ₀ + KΛ³, with K being a constant. Deformation of the polymer in the channel occurred with the formation of shear bands. At the preliminary draw ratio Λ = 1.82, the bands have been oriented at the angle 21.5° with respect to the stretching axis. The planar elongation has led to abnormally strong deformation softening of the polymer. The drawing has been accompanied by an increase in the elasticity modulus of the polymer. The obtained results have suggested that the macromolecules orientation is the main reason for strain hardening of the polymer.