Byung Mun Jung

Dispersion of single walled carbon nanotubes in organogels by incorporation into organogel fibers

We prepared hybrid organogels, where single walled carbon nanotubes (SWNTs) were incorporated into organogel fibers. The SWNTs were covalently functionalized with organic branches that had a similar structure to the organogelator. The effect of relative interactions between the carbon nanotubes (CNTs), organogelator, and solvent molecules on the hybrid organogel structure was investigated. Compounds 1 and 2 were synthesized from 3,4,5-tris(decyloxy)benzoic acid and 1,8-diaminooctane, as an organogelator and a functional group for SWNTs, respectively. Organogelator 1 showed excellent ability to gelate alkanes and alcohols. The pristine SWNTs were oxidized by acids to create carboxylic acid groups and functionalized covalently with compound 2 using thionyl chloride. Hybrid organogels of compound 1 with functionalized SWNTs (f-SWNTs) were prepared in decane and N,N-dimethylformamide (DMF). Transmission electron microscopy (TEM) images showed that the f-SWNTs in the hybrid organogel formed in decane were mainly located inside or on the surface of the organogel fibers, while the f-SWNTs in the hybrid organogel formed in DMF were distributed evenly over the sample. When an organogelator had a different chemical structure to that of an organic functional group on the SWNT surface, SWNTs existed as large aggregates, or long bundles, which were not incorporated inside of the organogel fibers.

Preparation of discotic metallomesogens based on phenacylpyridines showing room temperature columnar phases

Discotic metallomesogens were prepared by complexation of phenacylpyridine ligands with copper(II) and palladium(II) ions. Picoline derivatives with an alkoxy chain were prepared by the reaction of 5-hydroxy-2-methylpyridine with alkyl bromides. In a similar manner, methyl 3,4,5-trialkoxybenzoates were obtained from methyl 3,4,5-trihydroxybenzoates and alkyl bromides. 5-Alkoxy-2-methylpyridines were metallated with lithium diisopropylamine and reacted with methyl benzoates to give ligand compounds 1–3. Metal complexes Cu1–3 and Pd1–3 were prepared by complexation of the ligands with copper(II) acetate and palladium(II) acetate in tetrahydrofuran, respectively. The ligands did not form liquid crystals, but their metal complexes showed enantiotropic columnar hexagonal mesophases at room temperature. The metal complexes of phenacylpyridines showed a superior ability to self-assemble into ordered phases compared to their structural analogues, the salicylaldiminato complexes.Discotic metallomesogens were prepared by complexation of phenacylpyridine ligands with copper(II) and palladium(II) ions. Picoline derivatives with an alkoxy chain were prepared by the reaction of 5-hydroxy-2-methylpyridine with alkyl bromides. In a similar manner, methyl 3,4,5-trialkoxybenzoates were obtained from methyl 3,4,5-trihydroxybenzoates and alkyl bromides. 5-Alkoxy-2-methylpyridines were metallated with lithium diisopropylamine and reacted with methyl benzoates to give ligand compounds 1–3. Metal complexes Cu1–3 and Pd1–3 were prepared by complexation of the ligands with copper(II) acetate and palladium(II) acetate in tetrahydrofuran, respectively. The ligands did not form liquid crystals, but their metal complexes showed enantiotropic columnar hexagonal mesophases at room temperature. The metal complexes of phenacylpyridines showed a superior ability to self-assemble into ordered phases compared to their structural analogues, the salicylaldiminato complexes.

Molecular imprinting into organogel nanofibers

Molecularly imprinted organogel nanofibers were prepared using a polymerizable organogelator. A functional monomer having a similar structure to the organogelator was used for complexation with the template. The imprinted nanofibers showed a specific binding property for the template and a fast kinetic binding profile.

Enhancement of Magnetoelectric Conversion Achieved by Optimization of Interfacial Adhesion Layer in Laminate Composites

We report the effect of epoxy adhesion layers with different mechanical or physical property on a magnetoelectric (ME) composite laminate composed of FeBSi alloy (Metglas)/single-crystal Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3/Metglas to achieve an improved ME conversion performance. Through theoretical simulation, it was revealed that the Youngs modulus and the thickness of interfacial adhesives were major parameters that influence the conversion efficiency in ME composites. In the experimental evaluation, we utilized three epoxy materials with a distinct Youngs modulus and adjusted the average thickness of the adhesion layers to optimize the ME conversion. The experimental results show that a thin epoxy layer with a high Youngs modulus provided the best performance in the inorganic-based ME conversion process. By tailoring the interfacial adhesion property, the ME laminate generated a high conversion coefficient of 328.8 V/(cm Oe), with a mechanical quality factor of 132.0 at the resonance mode. Moreover, we demonstrated a highly sensitive alternating current magnetic field sensor that had a detection resolution below 10 pT. The optimization of the epoxy layers in the ME laminate composite provided significant enhancement of the ME response in a simple manner.

Multifunctional Epoxy-Based Solid Polymer Electrolytes for Solid-State Supercapacitors

Solid polymer electrolytes (SPEs) have drawn attention for promising multifunctional electrolytes requiring very good mechanical properties and ionic conductivity. To develop a safe SPE for energy storage applications, mechanically robust cross-linked epoxy matrix is combined with fast ion-diffusing ionic liquid/lithium salt electrolyte (ILE) via a simple one-pot curing process. The epoxy-rich SPEs show higher Youngs modulus ( E), with higher glass transition temperature ( Tg) but lower ionic conductivity (σdc) with a higher activation energy, compared to the ILE-rich SPEs. The incorporation of inorganic robust Al2O3 nanowire simultaneously provides excellent mechanical robustness ( E ≈ 1 GPa at 25 °C) and good conductivity (σdc ≈ 2.9 × 10-4 S/cm at 25 °C) to the SPE. This suggests that the SPE has a bicontinuous microphase separation into ILE-rich and epoxy-rich microdomain, where ILE continuous conducting phases are intertwined with a sturdy cross-linked amorphous epoxy framework, supported by the observation of the two Tgs and low tortuosity as well as the microstructural investigation. After assembling the SPE with activated carbon electrodes, we successfully demonstrate the supercapacitor performance, exhibiting high energy and power density (75 W h/kg at 382 W/kg and 9.3 kW/kg at 44 W h/kg). This facile strategy holds tremendous potential to advance multifunctional energy storage technology for next-generation electric vehicles.