Research articles

Two kind of cyclic tri-β-peptides, cyclo(β-Ala(nap)-β-Ala-β-Ala (C3NAA)), and cyclo(β-Ala(nap)-ED-SA) (C3NES), are synthesized. The orientation of the peptide nanotube bundles changes from horizontal to perpendicular on the guanidium-terminated SAM due to the methanol-vapor annealing process. The C3NAA nanotube bundles positioned horizontally along the gold substrate generate a relatively large surface potential, and the converse piezoelectric response is as high as approximately 9 pm/V.

Highly conductive, soft, and 3D-printable nanocomposite polymers have been developed that consists of poly (ionic liquid) (PIL), polymethylmethacrylate (PMMA) as polymeric system, multiwalled carbon nanotubes (MWCNTs) as fillers and an ionic liquid (IL) that acts as a plasticizer and dopant for the MWCNTs. The nanocomposites exhibited variable mechanical, conductive, and thermal properties depending on the composition of polymer, IL, and MWCNTs. Finally, we optimized the conditions for 3D printing and demonstrated the fabrication of a flexible, 3D-printed circuit, which can be bent and twisted without damaging the circuit.

PVA/MWCNT nanocomposite aerogels were fabricated via the ScCO₂ drying method. The aerogels were fully characterized, and their shape memory behaviors were examined. As the MWCNT content was increased, the electrical conductivity increased abruptly by up to 4 orders of magnitude, implying that an electrical percolation network had formed in the nanocomposite aerogels. The shape memory results illustrated the shape recovery ratio, and the recovery speed of the nanocomposite aerogels increased, due to the addition of the MWCNTs.

The possibility of detecting the interfacial glass transition of polystyrene with contact angle measurements of a liquid polyethylene glycol on the polymer surface was investigated. The observed contact angle reflects the deviation from an equilibrium state at low temperatures, exhibiting a discontinuous change in the temperature dependence of the interfacial tension. The evaluated T_g was ca. 362 K, which is lower than a calorimetric T_g for a bulk polystyrene. The interfacial glass transition appears to be detected when the polymer/liquid interactions affect the wetting process.

We studied the surface functionalization of PP by dip-coating with a maleic anhydride-grafted chlorinated polypropylene (MPO) /methacrylate-based terpolymer mixture. A methacrylate-based terpolymer (PMFP) was synthesized, which contained perfluoroalkyl (R_f)-conjugated monomers and poly(ethylene glycol)-conjugated monomers. We found that the presence of MPO aided the adhesion of the terpolymer to the PP surface and that the coated PP surface exhibited low protein-fouling properties. In addition, the dip-coating of a terpolymer containing reactive groups (–COOH) with MPO caused the reactive groups to be presented at an outermost surface.

Viscoelasticity of PEG in aqueous solutions containing different concentrations of K₂SO₄ was studied by QCM-D, after coating a rigid supported lipid bilayer on the silicon oxide substrate. The obtained viscoelastic properties of PEG in K₂SO₄ solutions agree well with the Zimm model predictions for linear polymer chains. The gradual worsening of solvent quality by adding K₂SO₄ to aqueous PEG solutions is demonstrated by the obtained excluded volume exponents via QCM-D and the conventional intrinsic viscosity measurements.

Diallylated p-coumaric acid (A2CM) and triallylated caffeic acid (A3CF) were thiol-ene photo-polymerized with a pentaerythritol-based tetrathiol (S4P) at allyl/thiol and (allyl+enone)/thiol ratios of 1/1. The FT-IR spectral analysis revealed that the reaction of allyl and thiol groups mainly progressed for the products cured at the allyl/thiol ratio of 1/1, while both allyl and enone groups reacted with thiol groups for the products cured at an (allyl+enone)/thiol ratio of 1/1. The A3CF/S4P cured at an allyl/thiol ratio of 1/1 exhibited the highest glass transition temperature, 5% weight loss temperature, tensile strength and modulus among all the cured products.

Porous hydrogels (CNF-PEG hydrogels) for the adsorption of metals from aqueous solutions were prepared from chitosan nanofibers (CNFs) and poly(ethylene glycol) diacrylate (PEGDA). CNF-PEG hydrogels adsorbed both transition metals (e.g., copper) and post-transition metals (e.g., tin). The adsorption capacity was observed to increase with increasing CNF/PEGDA ratio, indicating that the CNFs exhibit synergism between chelation between metals and chitosan, and the enlarged surface area of the porous structure.