The solvent qualities of the essential oil components α-pinene, β-pinene, and p-cymene for atactic polystyrene (a-PS) were investigated via polymer solution studies. The cloud-point curves in α-pinene were determined for two a-PS samples with weight-average molecular weight Mw = 3.85 × 104 and 9.62 × 104 over a polymer concentration range of 0.2–31%. Both curves exhibited upward-convex shapes characteristic of upper critical solution temperature phase behavior, with the higher-molecular-weight sample showing consistently higher cloud points, indicating that α-pinene is a poor (Θ) solvent for a-PS. The intrinsic viscosities [η] of a-PS samples with Mw values ranging from 3.85 × 104 to 4.13 × 106 in β-pinene and p-cymene at 25.0 °C fell between those in toluene, a good solvent for a-PS, and cyclohexane, a poor solvent, demonstrating that β-pinene and p-cymene are medium-quality solvents for a-PS. The higher [η] in p-cymene indicates better solvent quality, which can be attributed to its aromatic ring. The marked difference between the solvent qualities of the structural isomers α-and β-pinene indicates that molecular structure exerts a considerable influence on polymer–solvent interactions. A comparison with literature data suggests that increasing the steric bulkiness of alkyl substituents on aromatic hydrocarbons reduces their solvent quality for a-PS. The solvent qualities of α-pinene, β-pinene, and p-cymene for atactic polystyrene (a-PS) were investigated through polymer solution studies. α-Pinene was found to be a poor (Θ) solvent, whereas β-pinene and p-cymene were medium-quality solvents. The higher intrinsic viscosity in p-cymene suggests better solvent quality due to its aromatic ring. The marked differences in solvent quality among α-pinene, β-pinene, and p-cymene for a-PS suggest that the molecular structures of the solvents strongly affect polymer–solvent interactions.
The aim of the work was to obtain Hydrophilic Fast-absorbing Platforms (HFP) based on gelatin as a basis for effective colorimetric sensor systems for out-of-laboratory monitoring of toxins (atrazine). Four HFP series (HFP1-HFP4) were synthesized under different conditions. Cooling the gelatin solution to 5 SC produced a physical network of HFP1. HFP2, a rigid covalent network, was obtained by thermally curing gelatin with glutaraldehyde (GA). Formation of HFP3 occurred due to UV irradiation of gelatin and bisacrylamide (BAA), resulting in the structure of semi-interpenetrating polymer networks. HFP4 was obtained from gelatin and sodium carboxymethylcellulose (Na-CMC) using a combined system of crosslinkers (BAA and GA) and curing methods (heating and UV irradiation), yielding interpenetrating polymer networks. A crushed molecularly imprinted polymer selective for atrazine (MIPatr) was synthesized and integrated into the structure of the HFP. The morphology and water sorption capacity of individual and filled HFPs were studied. The morphology of the samples was examined using light microscopy. The degree of swelling (β) was determined by the gravimetric method. It was established that varying the formation conditions allows regulation of the matrix's pore architecture and hydrophilicity, which ensures a high mass transfer rate. All samples showed a general tendency to decrease water sorption in the order HFP1 > HFP3 > HFP4. The decrease in sorption indicates the compaction of the hydrophilic matrix. However, introducing the MIPatr filler into HFP2 changes the morphology and increases the sorption capacity of the system, forming a looser, porous structure. The HFP3 sample is the most promising, with the most balanced structure. Thanks to Na-CMC, the pores of GSHP4 are significantly larger than those of HFP1, HFP2, or HFP3, ensuring rapid delivery of atrazine to the MIPatr particles through these large pores. The MIPatr particles themselves will act as selective filters.
Ion-conducting membranes based on di- and triblock copolymers of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA), with varying PEO block lengths, were synthesised and their ionic conductivity at room temperature was investigated. The highest conductivity values for the studied membranes were found to range from 4.2·10−5 – 9.8·10−5 S·cm−1, depending on the copolymer architecture and environmental conditions. The ionic conductivity of the diblock copolymer membranes was further enhanced by the addition of lithium hexafluorophosphate. Increasing the lithium hexafluorophosphate content from 3 to 9 wt.% was shown to lead to a significant increase in conductivity, from 4.49·10−6 – 1.98·10−5 S·cm−1 due to an increase in the concentration of mobile ions, the plasticisation of the polymer matrix and improved dissociation of the copolymer's carboxyl groups in a saline environment. Additionally, the dielectric properties of the MePEO-b-PAK membrane were examined at different ambient humidity levels (33%, 65%, 81% and 98% relative humidity). It was determined that high humidity levels (81% and 98%) are unsuitable for the practical operation of these membranes as excessive water absorption deteriorates their mechanical and physicochemical properties. Conversely, moderate humidity increases ionic conductivity without significantly compromising the membrane’s integrity. These results highlight the importance of polymer architecture, salt content and environmental control in developing PEO-based polymer electrolytes, and provide useful guidance for designing ion-conducting membranes for use in fuel cells.
Polyimide composites based on two different polymer matrices and filled with carbon nanotubes (CNTs) were characterized by FTIR spectroscopy, X-ray diffraction, and thermogravimetric analysis, and their microwave characteristics were also investigated. The materials studied included composites based on a linear polyimide matrix containing 0.06 and 0.6 wt.% CNTs and a composite based on a polyimide matrix with cardo substituents containing 5 wt.% CNTs. The FTIR spectra of the investigated composites exhibited absorption bands characteristic of polyimides. X-ray diffraction analysis revealed changes in the diffraction profile with increasing CNT content in the linear PI matrix, as well as pronounced structural differences for the composite based on the PI with cardo substituents. The composite based on the polyimide with cardo substituents containing 5 wt.% CNTs exhibited higher thermo-oxidative stability during the main degradation stage, as well as higher levels of electromagnetic-wave absorption and reflection in the Ka-band compared with the composites based on the linear PI. The observed differences may result from the combined effects of the polymer-matrix structure and CNT content.
The use of polylactic acid (PLA) and polycaprolactone (PCL) as film-forming components in composites with thermoplastic starch (TPS) was investigated. An optimal composition of the functional additive in TPS was developed using chitosan and lactic acid (chitosan lactate, LC). The physical and mechanical properties of the PLA/TPS and PCL/TPS composites were determined. The structure of the composites and its changes following thermomechanical treatment were studied using FT-IR spectroscopy. Mass spectrometric analysis was performed, and the characteristic mass spectra of ion fragments resulting from the thermal decomposition of PLA, LC, and PLA/TPS were analyzed; their intensities at the peak region were measured. Structural changes in the compositions were studied using DSC and TGA methods, and the mass loss and rate of mass loss during thermal decomposition were quantitatively determined.
