Min Jae Shin

Reversible Chromatic Response of Polydiacetylene Derivative Vesicles in D2O Solvent.

The thermal chromatic sensitivity of polydiacetylenes (PDAs) with 10,12-pentacosadiynoic acid (PCDA) derivatives, which have a hydroxyl group (HEEPCDA) and an amine group (APPCDA), were investigated using D2O and H2O as solvents. The vesicle solution with polymerized HEEPCDA exhibited a reversible chromatic response during the heating and cooling cycle in D2O, but not in H2O. On the other hand, the vesicle solution with the polymerized APPCDA exhibited a reversible chromatic response in H2O during the heating and cooling cycle, but the color of the solution did not change much in D2O. The critical vesicle concentration of HEEPCDA was lower in D2O than in H2O, and the chromatic sensitivity of the polymerized vesicles to temperature was slower in D2O than in H2O. We think that it is due to D2O being a more highly structured solvent than H2O with the hydrogen bonding in D2O stronger than that in H2O.

Amperometric Cholesterol Biosensor Using Layer-by-Layer Adsorption Technique on Polyaniline-coated Polyester Films

An amperometric cholesterol biosensor was fabricated using polyaniline-coated polyester films. Polyaniline was dissolved in chloroform with camphorsulfonic acid, and polystyrene was added to this solution. Using this mixed solution, the coating was placed onto polyester films. Cholesterol oxidase was immobilized onto these films using an electrostatic layer-by-layer adsorption technique. Poly(diallyldimethylammonium chloride) was used as the counter ion source. The level of adsorption was examined and evidence of layer-by-layer adsorption was investigated using a quartz crystal microbalance (QCM). A cholesterol biosensor was fabricated from these films as a working electrode, and it was used to measure the cholesterol concentration.

Sensing Capability of Molecularly Imprinted Self-Assembled Monolayer Using Terphenylpropanethiol

A molecularly imprinted self-assembled monolayer (SAM) was fabricated on a gold plate by forming a monolayer with both thiol compound and the template molecule, and removing the template molecules by solvent extraction. 1-Dodecanethiol (DDT), 1-hexadecanethiol (HDT), [1,1′:4′,1′′-terphenyl]-4-thiol (TPT), and [1,1′:4′,1′′-terphenyl]-4-propanethiol (TPPT) were used as the thiol compounds. Cholesterol was used as the template molecule, and cholesterol, cholic acid, and deoxycholic acid were used as the substrate molecules. Cyclic voltammograms were obtained using these imprinted gold plates as a working electrode, with Ag/AgCl reference electrode and Pt counter-electrode. Potassium ferricyanide was used as a background material for oxidation and reduction. These imprinted monolayers were capable of discriminating cholesterol that had been imprinted. The order of sensing capability of the thiol compounds was TPPT > HDT > TPT > DDT.

Latent imidazole curing agents by microencapsulation with copolymers

ABSTRACT The encapsulation of imidazoles was conducted to prepare the latent imidazole curing agents by using the copolymers as the wall materials. The latent imidazole curing agents are essential to manufacturing anisotropic conducting films (ACFs). The copolymers, which were used for the encapsulation, were the copolymers of methacrylic acid (MAA) and octadecyl methacrylate (ODMA). The method for encapsulation was the spray-drying method. The curing behaviors of the microcapsules to epoxy resin were investigated using a differential scanning calorimeter (DSC). Using the encapsulated microcapsules, the curing reaction to epoxy resin was conducted at 150°C and 180°C, and the curing time was measured. The fabricated microcapsules using the copolymers showed an improved latent character compared with the previously reported results.

One-component epoxy adhesive for repair of cell phone board

Abstract The development of a one-component epoxy adhesive for cell phone board repair was described. The most important goal of this study is to obtain long storage stability in conjunction with the curing reaction process at a relatively low temperature of 95 °C. Bisphenol-A type, bisphenol-F type, and NBR-based epoxy resins were used as the basic resins. Dicyandiamide (DICY) was used as a curing agent, and 2-methylimidazole (2MI) was used as an accelerator. 2MI was encapsulated using a copolymer of methacrylic acid and dodecyl methacrylate to achieve latent curing performance. After mixing the epoxy resin with DICY and encapsulated 2MI, this curing system showed excellent storage stability with almost no viscosity increase for 2 months at 20 °C, and full curing was achieved at 95 °C for 50 min. We determined the optimum formulation of the epoxy adhesive for adhesion of a cell phone board after the measurement of physical properties.

Polymerizable ultraviolet stabilizers for unsaturated polyester-based bulk molding compounds

Monomeric compounds that protect against ultraviolet (UV) exposure, e.g. 2-hydroxy-4-acryloyloxybenzophenone (HABP), 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl methacrylate (BTEM), and 4-acryloyloxy-1,2,2,6,6-pentamethylpiperidine (APMP), were used as UV stabilizers for unsaturated polyester-based bulk molding compounds (BMCs). HABP and APMP were synthesized by reacting acryloyl chloride with 2,4-dihydro-xybenzophenone and 1,2,2,6,6-pentamethyl-4-piperidinol, respectively. The molded BMC samples were obtained using actual formulations containing these UV stabilizers, and the UV stability of the samples was estimated using a color difference meter. The results showed that HABP and BTEM afforded good protection against UV light, and these compounds showed a synergistic effect. APMP also showed a synergistic effect, but only when a small amount of the compound was used. These results were compared with the results obtained when copolymers of HABP and BTEM were used as UV stabilizers. The results showed that the polymerizable UV stabilizers demonstrated better protection against UV exposure, when they were added directly to the formulation of BMC, compared to the addition of copolymers as UV stabilizers.