Studies have shown the possibility of synthesizing new polymers based on polypropylene glycol maleate with acrylic acid in the presence of a RAFT agent (2-Cyano-2-propyl dodecyl trithiocarbonate CPDT). The effect of RAFT agent concentration on network density has been shown to be connected with product yield. Herein, the composition of the obtained copolymers was determined using FTIR spectrometry in combination with the chemometric method of partial least squares (or projection to latent structures). To investigate the synthesized hydrogels, the degrees of equilibrium swelling was studied. The resulting objects were characterized by infrared spectroscopy. The surface morphology of the polymers was studied and the pore sizes were estimated using scanning electron microscopy. The structure of the test samples was confirmed by NMR spectroscopy. The thermal stability of crosslinked polymers was determined using thermogravimetry.
For the first time, the kinetics of isothermal curing and thermal degradation of polyethylene glycol maleate (pEGM)–based systems and their composites with mineral fillers were investigated in the presence of a benzoyl peroxide/N,N-Dimethylaniline redox-initiating system. DSC analysis revealed that the curing process at 20 °C can be described by the modified Kamal autocatalytic model; the critical degree of conversion (αc) decreases with increasing content of the unsaturated polyester pEGM and in the presence of fillers. In particular, for unfilled systems, αc was 0.77 for pEGM45 and 0.60 for pEGM60. TGA results demonstrated that higher pEGM content and the incorporation of fillers lead to increased thermal stability and residual mass, along with a reduction in the maximum decomposition rate (dTGₘₐₓ). Calculations using the Kissinger–Akahira–Sunose and Friedman methods also confirmed an increase in the activation energy of thermal degradation (Ea): EKAS was 419 kJ/mol for pEGM45 and 470 kJ/mol for pEGM60, with the highest values observed for pEGM60 systems with fillers (496 kJ/mol for SiO2 and 514 kJ/mol for CaCO3). Rheological studies employing three-interval thixotropy tests revealed the onset of thixotropic behavior upon filler addition and an increase in structure recovery after deformation of up to 56%. These findings underscore the potential of pEGM-based systems for low-temperature curing and for the design of composite materials with improved thermal resistance.
30 March 2021 in Bulletin of the Karaganda University. "Chemistry" Series
This article considers someaspects of synthesis and characterizationof polylactide-co-glycolide nanoparticles immobilized withthe antituberculous drug isoniazid. The influence of some synthesis parameters of nanoparticles (the ratio of drug substance:polymer and surfactant concentration) onproperties of the obtained nanosomal drug form of isoniazid has been studied. Optimal conditions for obtainingthenanoparticles with the best physicochemical parameters such as: particle size, polydispersity, conversion, etc. have been found. These nanoparticlescan be used asdrug carriers.The results revealed thata polymer: drug ratio of 1:1 and the use of 3% Twin 80 are necessaryto obtain stable emulsions of nanoparticles of polylactide-co-glycolide with satisfactory characteristics. Average size of the obtained particles was 196.4 nm,and the polydispersity value was 0.323. The aggregation stability of nanoparticles during 4 hours at temperatures of 4ºC and 20ºC has been evaluated. The morphology of the obtained nanoparticles has been studied.Analysis of nanoparticles was characterized by various instrumental methods includinggas chromatography and thermogravimetrytechniques. The resulting nanoparticles of polylactide-co-glycolide immobilized with isoniazid are stable in time andcanprolong the action of the drug. In vitrorelease of isoniazid from polylactide-co-glycolide nanoparticles hasbeen studied.
30 September 2021 in Bulletin of the Karaganda University. "Chemistry" Series
The rheological behavior and low-temperature curing kinetics of poly(ethylene glycol fumarate)–acrylic acid systems initiated by benzoyl peroxide/N,N-dimethylaniline have been investigated for the first time with a focus on the development of thermosetting binders with controllable properties. It has been established that both composition and temperature have a significant effect on rheological behavior and kinetic parameters. Rheological studies revealed non-Newtonian flow behavior and thixotropic properties, while oscillatory tests demonstrated structural transformations during curing. Increasing the temperature was found to accelerate gelation, whereas a higher polyester content retarded the process, which is crucial for controlling the pot life of the reactive mixture. DSC analysis indicated that isothermal curing at 30–40 °C can be satisfactorily described by the Kamal autocatalytic model, whereas at 20 °C, at later stages, and at higher polyester contents, diffusion control becomes significant. The thermal behavior of cured systems was investigated using thermogravimetry. Calculations using the isoconversional Kissinger–Akahira–Sunose and Friedman methods confirmed an increase in the apparent activation energy for thermal decomposition, suggesting a stabilizing effect of poly(ethylene glycol fumarate) in the polymer structure. The studied systems are characterized by controllable kinetics, tunable viscosity, and high thermal stability, making them promising thermosetting binders for applications in composites, construction, paints and coatings, and adhesives.