Research articles

A novel surface wrinkling system, based on the fabrication of a polyion complex (PIC) skin layer, is introduced. PIC skin layers are fabricated on the surface of chitosan (CS) films via immersion in sodium alginate (AG) solutions. After removal of excess adsorbed AG, microscopic wrinkles appear upon drying. Water resistance in the wrinkled films was achieved by thermal crosslinking of the PIC skin layer. The thermally crosslinked wrinkled surfaces that were composed of covalently crosslinked CS and AG exhibited low cell adhesiveness and are suitable for use in implantable materials.

The deviant and irregular polymerization behavior of 4-acetoxystyrene was found through the detailed study on the ATRP of various para-substituted styrenes bearing electron-withdrawing and electron-donating groups. The relationship between the rate constant for polymerization rate and the Hammett parameter was discussed.

The effect of silica nanoparticle size and concentration on the mechanical strength and wellbore plugging performance of SPAM/ chromium (III) acetate nanocomposite gels was investigated. First, the rheological behavior of gelant, surface chemistry, morphology, and viscoelastic properties of synthesized nanocomposites were investigated. In addition, an experimental setup was designed to determine the maximum differential compressive pressure (DCP) that the synthesized nanocomposite gels can tolerate before failing. The nanocomposites containing 20–30 nm particles have a higher DCP in comparison to those having 7–10 and 60–70 nm nanoparticles.

We optimized the sonoporation of a suspension culture with microbubbles for labeling and MR tracking of mesenchymal stem cells (MSCs). When water was used as the transmission medium between the acoustic probe and cell suspension, microbubbles gently collapsed with minimal cell damage. Under this condition, the number of labeled MSCs was 25%, which is 3.3-fold greater than the number of MSCs labeled using the conventional electroporation system, and the cell viability was maintained at approximately 80%. The MRI signal could be clearly observed for 2.0 × 10⁶ MSCs.

Solution-cast gold-like lustrous films of oligo(3-methoxythiophene) were subjected to benzene exposure and benzene addition treatments. Both treatments provided films with a higher luster and more intense yellowness, i.e., an enhancement in a gold tone. Such a gold-tone-enhancing effect was explained by a model in which upon the treatments, the oligomers adopt a planar conformation through π–π interactions between benzene and the thiophene rings, and the resulting sandwich structures facilitate the formation of edge-on lamellar crystallites, the most likely gold-tone developing structure.

We prepared ionic conductive compound (ICC) by solution casting and the in situ polymerization of poly(ethylene glycol) methyl ether methacrylate (OEGMA) in the presence of PMMA and a cross-linking agent. Then, ionic conductive polymer blends was obtained by melt-mixing ICC and poly(L-lactic acid) (PLLA). We studied the relationship between phase structure and physical properties such as electrical and mechanical properties of the blends.

Microcellular and nanocellular silicone rubber foam are prepared by supercritical carbon dioxide in this work. The t_pre and P_s are important factors which affect the open-cell content (OCC). When the t_pre and P_s increases, the OCC sharply improves and could reach to more than 96%. The OCC has a significant effect on the mechanical properties of the nano/micro silicone rubber foam.

We discover a new cavitation phenomenon in amorphous polymers sandwiched between two thick slide glasses from the static melt induced by thermal treatment. By quenching atactic polystyrene samples from the static melt under the glass transition temperature (T_g) and annealing them above T_g, cavities are created to relax the negative pressure. Cavity growth undergoes an Ostwald ripening-like process in cases of large molecular weight while it undergoes a viscous fingering process in cases of small molecular weight.

The reactive groups (–OH or –NH₂) of natural melanin nanoparticles from cuttlefishes react with isocyanate groups in pre-polyurethane (pre-PU) to form cross-links, further strengthening the self-healing of PU based on the reversible acylhydrazone bond. The self-healing efficiency was improved from 91.73% to 99.58% due to the strong interactions between the MNs and PU.

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.