Modification of Thiol-Ene Ionogels with Octakis(methacryloxypropyl) Silsesquioxane

Abstract

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.

The Influence of Monomer Structure on the Properties of Ionogels Obtained by Thiol–Ene Photopolymerization

“…The lack of transparency of the materials indicates a phase separation occurring between the ionic liquid and the polymer matrix. Our previous works show that the thiol-ene polymerization process in the ionic liquid EMImNTf 2 proceeds as dispersion polymerization [7]. Dispersion polymerization begins as a homogeneous solution of monomer and the polymer phase separates during the polymerization process.…”

“…Our research group conducted research on ionogels synthesized by the thiol-ene photopolymerization method. The choice of this method allowed us to use its main advantages in the synthesis of gel polymer electrolytes [6,7]. By initiating the polymerization reaction with UV radiation, it is possible to carry out the process in a short time (in the order of minutes) and at room temperature, and therefore with low energy consumption.…”

“…The mechanical properties of the obtained ionogels were characterized by a punctureresistance test [7]. The measurements were carried out using the CT3 texture analyzer (Ametek Brookfield, Middleboro, MA, USA).…”

Optimization of the Properties of Photocured Hydrogels for Use in Electrochemical Capacitors

“…In order to characterize the mechanical properties of the obtained HPE, a puncture resistance test was conducted similarly to the procedure described in our previous paper [21]. Briefly, the measurements were performed with a CT3 Texture Analyzer (Ametek Brookfield).…”

“…The ionic conductivity of the HPE was investigated by electrochemical impedance spectroscopy (EIS) in the frequency range from 1 kHz to 1 MHz using the SP-300 potentiostat/galvanostat (Biologic) in accordance with the procedure described previously [21]. The experiment was performed in a two-electrode (stainless steel-316L) type electrochemical vessel at room temperature.…”