Ionic liquids (IL) are characterized by unique properties which are the reason for the continuous growth of interest in these compounds for a large variety of applications. However, in many applications there is a need for immobilization of IL within solid matrices while maintaining IL specific properties. Such stable solid-liquid materials are called ionogels. This review provides basic information about ionogels, their preparation, properties and application with an emphasis on ionogels with polymer matrices.

Photopolymerization of monomers in ionic liquids (ILs) leads to the formation of conducting ionogels. In the frame of our continuing investigations in this field we report the first example of thiol–ene polymerization in ILs. The work focuses on the polymerization kinetics and reaction mechanism. The model system is based on a difunctional thiol and a divinyl ether (to exclude ene homopolymerization) with spacers built from oxyethylene units. The photo-initiated polymerization was carried out in the presence of various amounts of imidazolium-based ILs and was compared to the polymerization in non-ionic solvents. It was found that the addition of the solvents to the investigated system accelerates the reaction; however, the reaction occurs faster in non-ionic solvents than in ILs. The accelerating effect is associated with the additional stabilization of a partial charge separation in the transition state and its magnitude is closely related to the Kamlet–Taft β parameter which describes the hydrogen bond accepting ability of the solvent. In the case of ILs, the stabilizing effect is exerted by the IL's anion. However, the imidazolium cation interacts with the ether oxygen of the monomer decreasing its stabilizing influence on the transition state (which is related to the Kamlet–Taft α parameter representing the hydrogen bond accepting ability). The knowledge of the presented relationships provides a tool for designing thiol–ene systems containing ILs.

The objective of this study was to characterize changes in the termination mechanism and in the rate coefficients during a light-induced polymerization occurring under continuous illumination and during the after-effect (after the irradiation has been discontinued) in the presence or in the absence of oxygen. The illumination was stopped at various double bond conversions. The polymerization of a model monomer-(diethylene glycol)dimethacrylate was analyzed using three termination models: monomolecular (I), bimolecular (II) and mixed (III) and the following parameters were estimated: k^m _t and k_p[P˙]₀ (Model I), k^b _t[P˙]₀ and k_p[P˙]₀ (Model II) and k^m _t, k^b _t[P˙]₀ and k_p[P˙]₀ (Model III), where k^m _t is the monomolecular termination rate coefficient, k^b _t is the bimolecular termination rate coefficient, k_p is propagation rate coefficient and [P˙]₀ denotes macroradical concentration at the beginning of the dark reaction. The parameters of the models were averaged over increasingly large dark conversion. Multistage statistical analysis of the results showed that over the conversion range studied, the bimolecular reaction was the main way of termination during continuous illumination, but during the after-effect termination mechanism changed with time of dark reaction from the bimolecular to the mixed one indicating an increasing importance of radical trapping. The obtained results suggest that oxygen accelerates the bimolecular termination, but pseudo first-order reaction with oxygen also contributes to the overall termination process. Moreover, the postpolymerization is more sensitive to negative influence of oxygen than the polymerization under continuous irradiation.

A comprehensive study of model systems based on poly(ethylene glycol) dimethacrylate and two methacryloxy-modified silicas (Aerosil R7200 and R711) were investigated to find possible correlation between the stability of the monomer/silica dispersion, curing kinetics, composite morphology and physical and mechanical properties of the final hybrid material. The monomer/silica dispersions were cured photochemically. The investigated parameters: Zeta potential, polymerization rate and conversion, glass transition, surface roughness and mechanical properties were found to be synchronous; when plotted as function of silica content, they showed maxima or changes in the trend at the same filler loading. This threshold (optimum) silica content in the composition was about 5 wt.-% for the investigated systems. The results obtained are discussed in terms of the solvation cell (which influences dispersion stability) and the interphase layer formation as well as their changes below and above of the threshold filler content.