Polymer Science, Series B最新文献

The features of ethylene polymerization in the presence of dichloridobis(salicylaldaryliminato)titanium(IV) complexes containing a 4-allyloxy-2,3,5,6-tetrafluorophenylimino group, namely, {2‑[(4-CH₂=CH-CH₂O)C₆F₄N=CH]-6-R¹-4-R²-C₆H₂O}₂TiCl₂ (R¹ = t-Bu, CMe₂(Ph); R² = H, Me, OMe, t-Bu, CMe₂(Ph), Cl, Br) in the presence of methylalumoxane, have been studied. All the complexes exhibit high catalytic activity (up to 27.8 × 10⁶ g_PE ({text{mol}}_{{{text{Ti}}}}^{{ - 1}}) ({text{MPa}}_{{{{{text{C}}}_{2}}{{{text{H}}}_{4}}}}^{{ - 1}}) h^–1) in the temperature range of 10‒60°C and form powdered ultrahigh molecular weight polyethylene (UHMWPE) (M = (4.4–16.0) × 10⁶ g/mol) with a low number of intermolecular entanglements. It has been shown that during polymerization, the complexes are immobilized on UHMWPE macromolecules.

A series of oxybis benzoic aromatic polyesters were prepared by a two-step polymerization method of esterification and polycondensation, using 4,4'-oxybis(benzoic acid) (OBBA) and aliphatic diols with different carbon chain lengths (C2-8) as monomers, and tetrabutyl titanate (TBT) as catalyst. The results showed that the M_n of the prepared polyester was between 25350–42040 g/mol, and the polymer dispersity index (PDI) was about 2.0. The results of DSC, WAXD and UV–Visible spectroscopy showed that polyethylene oxybisbenzoic (PEO), polypropylene oxybisbenzoic (PPO), polybutylene oxybisbenzoic (PBO), polypentene oxybisbenzoic (PPeO) and polyhexene oxybisbenzoic (PHO) polyesters were amorphous, and the transmittance at 550 nm (T₅₅₀) were 75.0–85.2%, showing good light transmittance. The crystallization rate of polyheptylene oxybisbenzoic (PHeO) and polyoctylene oxybisbenzoic (POO) was slow, which changed from amorphous to semi-crystalline after been placed at room temperature for 10 days, resulting in no transparency. With the increase of carbon chain number of diols in polyester, the T_g of polyesters decreased gradually. TGA test results showed that PEO polyester had higher thermal stability (T_5% = 407.8°C, T_d = 441.9°C). The Young’s modulus and tensile strength of the polyester gradually decreased with the increase of the number of diol carbon chains. The elongation at break of polyesters with odd carbon chain diols was low (<20%), while the elongation at break of polyester with even carbon chain diols gradually increased from 4.2 to 1230.2%, which changed from brittle material to ductile material. The rheological properties analysis showed that the aromatic polyesters were typical pseudoplastic fluids.

The conditions to prepare luminescent acrylate polymers containing the organic dyad, molecule of which combines two different emitting fragments, hydroxyl-substituted 2,4,5–triarylimidazole and 8-azomethine-7-hydroxycoumarine moieties, via photocuring have been optimized. The effect of the nature of the photocured network acrylate polymers on luminescent properties of the dyad has been investigated. The prepared aliphatic network polymers have exhibited independent fluorescence of both molecule fragments, dependent on the excitation wavelength. At the same time, the aromatic network polymers and the aliphatic network polymers containing ether links have revealed only the imidazole fragment fluorescence. The fluorescence nature has been stronger dependent on the polymer repeat unit structure and the content of the aromatic fragments in the polymer matrix than on the presence of the hydroxyl groups in the polymer. It has been shown that the emission of the imidazole fragment of the dyad in the aliphatic network polymers depends on the internode distance and conditional polarity of the medium.

Balanced high transparency, thermal properties and organosolublility are urgent requirements for preparing polyimides. In this study, a series of fluorinated polyimides (V_a-f) containing a multi-ether fluorinated diamine unit were designed. The corresponding PIs were synthesized through traditionally thermally polycondensation with bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]ether (II) and various commercial aromatic dinahydrides (III_a-f). In particular, there are four rigid benzene rings and three flexible ether linkages in its fluorinated diamine structure (II), which is expected to achieve a balance in organic solubility and thermal properties. V_a-f had inherent viscosity ranging from 0.88 to 1.24 dL/g. In addition, these fluorinated PIs exhibited high organo-solubility in common organic solvents and mechanical properties of tensile strengths of 92–116 MPa, tensile moduli of 2.0–42.3 GPa, elongations at break of 10–36%. Meanwhile, they also exhibited glass transition temperatures (T_gs) of 215–265°C, 10 wt % weight-loss temperatures of 525–597°C in N₂. Among these PI films, V_f appeared excellent optical transparency, which displayed the cut-off wavelength at 361 nm with b* value of 8.7. For a comparative study, nonfluorinated analogous polyimides VI_a-f were also synthesized. As a result, the fluorinated V series showed better organo-solubility, better optical property, lower dielectric constant and lower moisture absorption but without scarified thermal properties. Such attractive comprehensive properties make these fluorinated PIs as potential candidates for application in microelectronics industry.

Features of the polymerization of methyl methacrylate and a number of other (meth)acrylate monomers in the presence of catalytic systems based on phenazine dyes (Neutral Red and Safranin Т) under visible light irradiation are investigated. It is shown that amines of various structure as well as air oxygen affect the kinetic features of polymerization and the molecular weight characteristics of polymers. It is found that polymerization may proceed in the controlled mode up to high conversions at room temperature and a low photocatalyst concentration, among them without preliminary degassing of the reaction medium.

Aromatic polyamidines based on 4,4′-diphenylmethane diisocyanate and bisamides have been synthesized and studied. The one-step reaction of bisamides with diazocyanate according to the [2+2]-cycloaddition mechanism includes a concerted process of the formation of two new σ-bonds in the transition state. The formation of polyamidine occurs as a result of decarboxylation, which completes this reaction. Due to the availability of starting compounds, ease of synthesis, good solubility, and high heat resistance and thermal stability of the resulting polymers, there are wide opportunities for producing new materials by conventional industrial processes. Polyamidines have a sufficiently large set of important technological properties, which suggest their greater potential in relation to applied problems. The resulting film materials and glass-reinforced plastics based on polyamidines show high mechanical properties that are not inferior to those of materials made from commercial polyamides and polybenzimidazoles.

In recent years, there has been considerable interest in conducting polymeric materials containing conjugated bonds. Imine polymers, in which nitrogen atoms are incorporated into the conjugated system, offer a different approach to the formation of materials with equally interesting electronic and optical properties due to the –CH=N– group being isoelectronic with the –CH=CH– group. In this study, a polyazomethine copolymer was prepared by a polycondensation reaction using ortho-tolidine and thiophene-2,5-dicarboxaldehyde catalyzed by Maghnite H+. The effect of time, temperature, amount of Maghnite H+, and solvent on the produced copolymer material was investigated. The optical, structural, and morphological properties of the copolymer, as well as the size of the particles, were investigated using various techniques, including ¹H NMR and FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy, X‑ray diffraction, and UV–Vis absorption. The optical band gap value was found to be around 2.54 eV.

The influence of the substituents inductive effect and the proton-donor OH group in the substituted cyclocarbonates differing in the alkyl chain length on the activation barrier of their aminolysis reaction, which underlies the process of urethane formation without the participation of isocyanates, has been studied. Account for the solvent molecules has allowed quantitative interpretation of the process regularities. Kinetics of the model aminolysis reaction of a series of monomers in DMSO has been investigated.

In this investigation, methylene blue (MeB) dye degradation under simulated solar light irradiation was experimentally investigated for the photocatalytic activity of poly(vanillin pyrrole)/ZnO nanocomposite. Conducting polymers like poly(vanillin pyrrole) (PPHMB) and its derivatives are often employed as photosensitizers to enhance the photocatalytic activity of ZnO when exposed to sunlight. The co-precipitation approach was used to create the PPHMB/ZnO composite after the PPHMB was created using the cationic polycondensation method. Under sunlight irradiation, the produced composite demonstrated greater photocatalytic activity than bare ZnO for the destruction of MeB dye. A variety of characterization methods, including, XRD, TGA, and an optical analysis, were used to the produced composite. Different operational factors that might influence results, such as the starting dye concentration, the amount of radiation employed, and the impact of the dosage of PPHMB/ZnO composite, have also been explored. A UV-visible spectrophotometer was used to determine the optical density of dye degradation. Additionally, investigated was the photocatalytic activity’s repeatability.

To increase the range of applications of bio-based polymer materials by attributing them self-healing ability is an efficacious way. It is an effective method to use Diels-Alder reaction for self-healing. However, self-healing materials synthesized by multifunctional monomers with Diels-Alder groups possess a low use temperature due to reversibility of DA bonds. In this study, the branched poly(furfuryl methacrylate) was synthesized from furfuryl alcohol, which is a biobased raw material prepared from crops. Using poly(furfuryl methacrylate) and bismaleimide, biobased self-healing polymeric materials were synthesized successfully based on the Diels-Alder reversible reaction. The Diels-Alder direct and reverse reactions occurred upon heating, resulting in self-healing of cracks on the polymer coatings. The thermal stability and use temperature of materials were also improved. All results demonstrated that synthesized materials possessed the characteristics of thermo-reversibility and self-healing and held great potential for self-healing coating applications.