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.
Highlights
Hybrid organic–inorganic ionogels are considered to be a new class of hybrid material, containing solid matrix and physically entrapped ionic liquid (IL) that keep their unique properties
Comparing the results obtained for capacitors with both ionogels, we can clearly see that electrochemical capacitors (EC) present similar capacitance/energy at a low value of current density (I), scan rate (v), or power (P)
With increasing of these parameters (I, v, P) we can observe the greater difference in obtained values of capacitance and energy, with better results obtained for EC with ionogel containing 1.5 wt.% of methacryl-polyhedral oligomeric silsesquioxane (POSS)
Summary
Hybrid organic–inorganic ionogels are considered to be a new class of hybrid material, containing solid matrix (organic–inorganic nanoparticles in the polymer) and physically entrapped (immobilized) ionic liquid (IL) that keep their unique properties. Hybrid ionogels can be obtained by an in situ process based on the polymerization of monomers and fillers dissolved/dispersed in ILs. Classical radical photopolymerization involving (meth)acrylates, represents a valuable approach that exhibits unique spatial, temporal control by means of a chain-growth mechanism, low-temperature cure, and energy efficiency. Classical radical photopolymerization involving (meth)acrylates, represents a valuable approach that exhibits unique spatial, temporal control by means of a chain-growth mechanism, low-temperature cure, and energy efficiency This process is widely used for a range of applications (coatings, inks, adhesives, dental materials, photolithographic processes) [1,2,3,4,5,6]. Photopolymerization of (meth)acrylates has several drawbacks, including inhibition of the polymerization by oxygen, the presence of unreacted monomer after curing following cure (in the areas not accessible to light), significant shrinkage that occurs during the polymerization process, and the formation of highly heterogeneous polymer networks [7,8,9,10,11]
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