Polymer Science, Series B最新文献

Carboxylic polyelectrolytes, water-soluble copolymers of acrylic acid and N-substituted acrylamides, were synthesized for the first time by reactions in the chains of poly(acrylic anhydride) with aromatic amines. The structure, composition, and molecular weight characteristics of the copolymers were determined. The possibility of synthesizing alternating copolymers of acrylic acid was demonstrated. The copolymers of varying composition characterized by low cytotoxicity and activity against herpes simplex virus were prepared.

A novel catalyst system containing a complex of Ti⁴⁺ with a (O,N,O)-tridentate phenoxyimine ligand and a binary Al(C₂H₅)₂Cl/Mg(C₄H₉)₂ activator at a molar [Al]/[Mg] ratio of ~3 affords the synthesis of ethylene polymers with molecular weight in excess of 1 × 10⁶. Ethylene homopolymer produced at 35°C has M_w ~ 2.6 × 10⁶ and ethylene copolymers with small amounts (below 1 mol %) of 1-hexene, 1-octene and 1-decene have M_w ~ 1.5 × 10⁶. The polymers have a relatively narrow molecular weight distribution (M_w/M_n ratio from 3.5 to 5), their mechanical properties are similar to properties of commercial UHMW polyethylenes.

The peroxyoxalate chemiluminescent reaction is an excellent source of excitation for photosensitizers used in theranostics for identification and targeting of tumor cells that produce elevated amounts of hydrogen peroxide. However, the substrates of peroxyoxalate chemiluminescent reaction, aromatic oxalates, are highly susceptible to hydrolysis in aqueous surroundings. Solubilization of oxalates in nanoreactors with a hydrophobic core significantly reduces their degradation by water. In this study, we compared for the first time the efficiency of the peroxyoxalate chemiluminescent reaction in emulsion and micellar nanoreactors. Two oxalates were studied herein, i.e. a highly active bis(2,4,5-trichloro-6-(pentyloxycarbonyl)phenyl) oxalate (CPPO) and nearly 15-fold less active but bioinspired tyrosine-based oxalate (BTEE-ox), which differed significantly in the pK_a of the leaving phenolic group, cytotoxicity, and hydrophobicity. Encapsulation of both oxalates into emulsion nanoreactors increased stability of both oxalates approximately by two orders of magnitude as compared to a THF/water (4 : 1) homogeneous solution. However, the emulsion underwent colloidal destabilization due to Ostwald ripening. In contrast, polylactide-block-poly(ethylene glycol) micelles exhibited excellent colloidal stability and ensured low rate of oxalates hydrolysis. The chemiluminescence activity of BTEE-ox solubilized in micelles became even higher than that of CPPO indicating that solid nanoreactors influenced the peroxyoxalate chemiluminescent reaction efficiency.

MQ resins have proved to be promising fillers for obtaining molecular composites based on silicone and carbon-chain rubbers. In the present work, MQ copolymers play the role of a complex filler with an inorganic core (Q unit) and an organic shell (M unit). Copolymers, in which the ratio of M and Q units was 1 : 2, 1 : 3, and 1 : 4, were used as fillers. Grafted methyl and decyl groups made it possible to use the MQ copolymer as a reinforcing filler of a carbon-chain polymer, polyisoprene. The thermal and rheokinetic behavior of filled compositions during the transformation of elastomers into rubbers was studied. Using differential scanning calorimetry and rheology techniques, the temperature parameters of the crosslinked structure formation process were determined and the values of the apparent activation energy of the crosslinking process were calculated. Increasing the proportion of the inorganic component from 1 : 2 to 1 : 4 resulted in an increase in the storage modulus of the crosslinked composites.

This article focused on preparing high-ortho phenolic resin using phenol and formaldehyde as precursors and using zinc acetate as catalysts. High ortho-phenolic fibers were produced through wet spinning, solution thermal curing (STC), microwave thermal curing (MTC), and heat treatment techniques. The structural and mechanical properties of the fibers were evaluated using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), micro-infrared imaging (Micro-FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TG), mechanical testing and scanning electron microscopy (SEM). The high-ortho phenolic fibers experienced a reduction in hydroxymethyl groups and an augmentation in methylene groups upon microwave curing, which enhanced cross-linking. Through the escalation of solution cross-linking bath and heat treatment, the hydroxymethyl groups within the phenolic molecules underwent a reaction to form methylene groups. Methylene groups facilitated the increase of intramolecular crosslinking degree, thereby enhancing the stability of the fibers structure. As a result, the mechanical properties of the fibers were improved and reached an optimal level under microwave heat curing, with an elongation of 3.1% and a tensile strength of 107 MPa.

Reducing the stress defects of grain caused by high temperature curing is of great significance to the safety and performance of propellant. Here, a series of alkenyl polyethylene glycol copolymers (APEG) were designed and synthesized using polyethylene glycol (PEG) samples and allyl glycidyl (AGE) and glycidol as raw materials. The APEG copolymers were cured at room temperature with nitrile oxide prepared in situ from p-benzenedinitrile oxide and triethylamine. The chemico-physical properties of the precursors and cured systems were discussed. The results showed that the tensile strength, the elongation at break and hardness decreased from the case of PEG 400 to the case of PEG 4000 and increased from the case of PEG 4000 to the case of PEG 6000. And the elongation at break of the cured APEGs decreased, the tensile strength increased with the increase of curing agent’s contents. The in situ IR of this cured system was analyzed and k = 0.1888 g/(mol min) at 27°C. The initial thermal decomposition of this cured system was also discussed. The activation energy and reaction order were calculated respectively as 163.886 kJ/mol and 0.96. The results suggested that the prepared binder could be cured rapidly at room temperature and had greater heat release during high temperature decomposition. Based on the excellent room curing performance and great heat release of this work, The APEG copolymers provide a feasible strategy to solve the problems caused by the high temperature curing.

It has been shown that adamantane-containing diamines are highly reactive under conditions of single-stage high-temperature cyclization in a sulfolane–toluene mixture of solvents. Polyimides with the reduced viscosity of 1.3‒1.4 dL/g have been synthesized on their bases, the films of which have exhibited good thermal properties and low yellowness index (1.1‒1.2).

To extend the service life of concrete in harsh environments, this paper introduces a silicone-modified polyurethane with self-repairing capabilities. The integration of silicone and disulfide bonding into the polyurethane molecular chain endows the material with a self-repairing ability and hydrophobicity. The incorporation of silicone significantly enhances the polyurethane’s hydrophobicity, while the introduction of disulfide bonds enables damage repair under mild conditions, and the repair efficiency can reach 90%. This combination of hydrophobicity and self-repairing properties holds paramount importance in protecting concrete and ensuring its prolonged use.

In the description of multicenter ion-coordination polymerization of isoprene on the catalytic system GdCl₃· n(i-C₃Н₇OH)‒Al(i-C₄H₉)₃ the inverse kinetic task for the scheme of a process with slow initiation has been solved. The task of determining the number of active centers of polymerization was solved by deconvolution of experimental MWDs through superposition of Flory distributions. It has been shown that four types of active centers participate in polymerization, the kinetic difference of which in the process of formation of polymer fractions with their characteristic average molecular weights and the most probable MWD, is associated with their difference in the concentrations of pre-reaction catalytic centers and the rate constants of reactions occurring on them. For each type of active centers, partial conversions of monomer consumption and rate constants of initiation, chain propagation, and chain transfer to the monomer are determined.

In light of the persistent challenges in herbicide release control, this study aims to investigate the factors influencing the release rate of herbicides from polymer–montmorillonite clay composites. Understanding these factors can provide valuable insights for the development of improved controlled release systems, offering enhanced precision and efficiency in herbicide delivery. Polymer-montmorillonite clay composites carrying 2,4-dichlorophenoxy acetic acid as controlled release systems were prepared by in-situ polycondensation. The intercalated polymeric 2,4-dichlorophenoxy acetic acid composites were characterized using various analytical techniques. Release studies were conducted in aqueous media at different pH levels over an extended period of approximately 80 days. The results revealed the significant influence of various factors on the release rate of the herbicide, including polymer structure, medium composition, percentage of polymer grafting onto clay, clay-to-polymer ratio, and swelling behavior. These findings have important implications for the development of controlled release systems for herbicides. Understanding the factors influencing release rates enables the optimization of composite design and formulation for efficient herbicide delivery. Moreover, this research provides a foundation for future investigations aimed at enhancing the release performance and overall effectiveness of polymer-montmorillonite clay composites. Potential avenues for further research include exploring tailored polymer structures, modifying the clay matrix, and optimizing the clay-to-polymer ratio.