In this work, we report the synthesis of polymerizable ionic liquids (PILs) and the synthesis of ionogels by thiol–ene photopolymerization.

The effect of polyhedral oligomeric silsesquioxane (POSS) on the synthesis and properties of hybrid organic–inorganic ionogels was investigated using octakis(methacryloxypropyl) silsesquioxane (methacryl-POSS). Ionogels were prepared in situ by thiol-ene photopolymerization of triallyl isocyanurate with pentaerythritol tetrakis(3-mercaptopropionate) in a mixture of imidazolium ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImNTf₂) and propylene carbonate (PC). Investigations included the kinetics of hybrid materials formation and selected physical and mechanical properties. The disadvantage of ionogels without the methacryl-POSS modifier is leakage and insufficient mechanical properties. Modifying the thiol-ene matrix by the addition of methacryl-POSS made it possible to obtain non-leaking ionogels with improved mechanical and conductive properties. The steric hindrance of POSS cages and high-density network formation played important roles in ionogel synthesis: decrease of polymerization rate (with almost no effect on conversion), as well as dimensions of the formed polymer spheres during dispersion polymerization (highly cross-linked polymer has poorer solubility in polymerizing medium at a similar conversion, and nucleation begins at lower conversion), an increase of glass transition temperature and puncture strength. Hybrid ionogels with high ionic conductivity in the range of 4.0–5.1 mS∙cm⁻¹ with the maximum parameter for 1.5 wt.% addition of the methacryl-POSS were obtained, which can be associated with ion-pair dissociations in ionic liquid clusters caused by methacryl-POSS.

In this work, hydrogel polymer electrolytes (HPEs) were obtained by the photopolymerization of a mixture of two monomers: Exothane 8 (Ex8) and 2-hydroxyethylmethacrylate acid phosphate (HEMA-P) in an organic solvent N-methyl-2-pyrrolidone (NMP), which was replaced after polymerization with water, and then with the electrolyte. The ratio of monomers as well as the concentration of NMP was changed in the composition to study its influence on the properties of the HPE: conductivity (electrochemical impedance spectroscopy, EIS) and mechanical properties (puncture resistance). Properties were optimized using a mathematical model to obtain a hydrogel with both good mechanical and conductive properties. To the best of our knowledge, it is the first publication that demonstrates the application of optimization methods for the preparation of HPE. Then, the hydrogel with optimal properties was tested as a separator in a two-electrode symmetric AC/AC pouch-cell. The cells were investigated by cyclic voltammetry galvanostatic charge/discharge with potential limitation and EIS. Good mechanical properties of HPE allowed for obtaining samples of smaller thickness while maintaining very good dimensional stability. Thus, the electrochemical capacitor (EC) resistance was reduced and their electrochemical properties improved. Moreover, photopolymerization kinetics in the solvent and in bulk by photo-DSC (differential scanning calorimetry) were performed. The great impact on the polymerization of HEMA-P and its mixtures (with Ex8 and NMP) have strong intermolecular interactions between reagents molecules (i.e., hydrogen bonds).

Flexible ionogels with good mechanical properties were obtained in situ by thiol-ene photopolymerization of trimethylolpropane tris(3-mercaptopropionate) (TMPTP) and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATT) (with C=C: SH ratio 1:1) in four imidazolium ionic liquids (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide—EMImNTf₂, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate-EMImOTf, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide-BMImNTf₂, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate—BMImOTf) used in the range 50 to 70 wt.%. The mechanical and electrochemical properties of obtained ionogels were examined. Ionogels with ionic liquids (ILs) with NTf₂⁻ anion are more puncture resistant than with OTf⁻ anion. Moreover, ionogels with the NTF₂⁻ anion have better electrochemical properties than those with the OTf⁻ anion. Although it should be noted that ionogels with the EMIm⁺ cation have a higher conductivity than the BMIm⁺. This is connected with intermolecular interactions between polymer matrix and IL related to the polarity of IL described by the Kamlet-Taft parameters. These parameters influence the morphology of the polymer matrix (as shown by the SEM micrograph), which is formed by interconnected polymer spheres.

In this work, squaric acid (3,4-dihydroxycyclobut-3-ene-1,2-dione) was used as a coformer to pyridine carboxylic acid cocrystallization. Among three newly prepared complexes are an example of a salt–cocrystal continuum – pyridinium-2-carboxylate squaric acid adduct (1) and two ionic complexes – pyridinium-3-carboxylic acid hydrogen squarate hemihydrate (2), and pyridinium-4-carboxylic acid hydrogen squarate (3). X-ray structural analysis showed that picolinic acid exists in 1 as a zwitterion. In turn, pyridine carboxylic acids in 2 and 3 are in a cationic form. In the structures optimized at the APF-D/6-311++G(d,p) level of theory, no proton migration between the acid molecules is observed (molecular complex, or cocrystal), while single-crystal X-ray diffraction studies showed that proton transfer takes place and the obtained systems are called the hydrogen-bonded ion pair. The frontier molecular orbitals (HOMO and LUMO) were also analyzed. The global reactivity parameters (chemical potential, global hardness, global softness, global electrophilicity index, and maximum charge transfer index) were considered. The experimental and computed infrared spectra were compared. Additionally, the high thermal stability of novel squaric acid complexes was confirmed by thermogravimetric and differential scanning calorimetry methods. The preliminary studies on the fungistatic activity showed inhibiting properties against Poria placenta.