Nam Ju Jo

Coating of Methyltriethoxysilane—Modified Colloidal Silica on Polymer Substrates for Abrasion Resistance

Organic-inorganic hybrid composites were prepared by the sol-gel method for the hard coating agent of transparent plastic, and their abrasion resistance, optical and surface characteristics were evaluated. Methyltriethoxy-silane (MTES) and colloidal silica were used as starting materials. The addition of MTES to colloidal silica enabled the formation of dense thin films with very smooth surface on the substrates. The thin films were strongly adhered to the substrates without primer treatment. The abrasion resistance increased with the increase in the ratio of MTES to the colloidal silica. Optimal amount of MTES for the hard coating agent was 100 wt% to the colloidal silica. The addition of curing catalyst, tetramethylammonium formate was found to be very effective to enhance the adhesion strength of coating agent to the substrates and reduced curing time.

Polyimide Multilayer Thin Films Prepared via Spin Coating from Poly(amic acid) and Poly(amic acid) Ammonium Salt

Polyimide (PI) multilayer thin films were prepared by spin-coating from a poly(amic acid) (PAA) and poly(amic acid) ammonium salt (PAAS). PI was prepared from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) PAA. Different compositions of PAAS were prepared by incorporating triethylamine (TEA) into PMDA-ODA PAA in dimethylacetamide. PI multilayer thin films were spin-coated from PMDA-ODA PAA and PAAS. The PAAS comprising cationic and anionic moieties were spherical with a particle size of 20≈40 nm. Some particles showed layers with ammonium salts, despite poor ordering. Too much salt obstructed the interaction between the polymer chains and caused phase separation. A small amount of salt did not affect the interactions of the interlayer structure but did interrupt the stacking between chains. Thermogravimetric analysis (TGA) showed that the average decomposition temperature of the thin films was 611 °C. All the films showed almost single-step, thermal decomposition behavior. The nanostructure of the multilayer thin films was confirmed by X-ray reflectivity (XRR). The LF 43 film, which was prepared with a 4:3 molar ratio of PMDA and ODA, was comprised of uniformly spherical PAAS particles that influenced the nanostructure of the interlayer by increasing the interaction forces. This result was supported by the atomic force microscopy (AFM) data. It was concluded that the relationship between the uniformity of the PAAS particle shapes and the interaction between the layers affected the optical and thermal properties of PI layered films.

Copolymerizations of ethylene with 1-hexene overansa-metallocene diamide complexes

We have performed copolymerizations of ethylene with 1-hexene using variousansa-metallocene compounds in the presence of the non-coordinative [CPh3][B(C6F5)4] ion pair as a cocatalyst. The metallocenes chosen for this study are isospecific metallocene diamide compounds,rac-(EBI)Zr(NMe2)2 [1, EBI = ethylene-1,2-bis(1-indenyl)],rac-(EBI)Hf(NMe2)2 (2),rac-(EBI)Zr(NC4H8)2 (3), andrac-(CH3)2Si(1-C5H2-2-CH3-4-tC4H9)2 Zr(NMe2)2 (4), and syndiospecific metallocene dimethyl compounds, ethylidene(cyclopentadienyl)(9-fluorenyl) ZrMe2 [5, Et(Flu)(Cp)ZrMe2] and isopropylidene(cyclopentadienyl)(9-fluorenyl)ZrMe2 [6,iPr(Flu)(Cp)ZrMe2]. The copolymerization rate decreased in the order4 >1 ∼3 >2 >5 >6. The reactivity of 1-hexene decreased in the order2 >6 >1 ∼3 ∼5 >4. We characterized the microstructure of the resulting poly(ethylene-co-1-hexene) by13C NMR spectroscopy and investigated various other properties of the copolymers in detail.

Actuation Behavior of CP Actuator Based on Polypyrrole and PVDF

Conducting polymer (CP) actuators undergo volumetric changes due to the movement of dopant ions into the film during the electrical oxidation process. In this work, PPy/SPE/PPy electroactive tri-layer actuator was prepared by the electrochemical polymerization of pyrrole and the actuation characteristics were studied. An all-solid actuator, consisting of two polypyrrole (PPy) films and a solid polymer electrolyte (SPE) based on poly(vinylidene fluoride) (PVDF), clearly showed a reversible displacement in an atmosphere when a voltage was applied.

Fluorescence Spectroscopic and Atomic Force Microscopic Studies on the Microstructure of Polyimide/Silica-Titania Ternary Hybrid Composites

Biphenyltetracarboximide-phenylene diamine polyimide/silica-titania ternary hybrid composites were prepared by thermal imidization and sol-gel reaction. Fluorescence spectroscopic, scanning electron microscopy, and atomic force microscopy studies revealed that the addition of small amount of titania showed profound effects on the microstructure and photophysical behaviors of polyimide/silica hybrid composites, when the content of silicatitania mixture was small or when the ratio of silica to titania in the mixture was high.

Properties of Waterborne Polyurethane Adhesives with Aliphatic and Aromatic Diisocyanates

A series of waterborne polyurethane (WBPU) adhesives were prepared with various ratios of aliphatic/aromatic diisocyanates, namely 4,4′-dicyclohexylmethane diisocyanate (H12MDI) as an aliphatic diisocyanate and 4,4′-diphenylmethane diisocyanate (MDI) as an aromatic diisocyanate with poly(tetramethyleneoxideglycol) (PTMG), ethylene diamine (EDA) and dimethylol propionic acid (DMPA). 1H-NMR spectroscopy was utilized to investigate the side reaction at the dispersion step during synthesis of WBPU dispersions with respect to aliphatic, aromatic and mixed diisocyanates. The tensile strength, Youngs modulus, elongation at break (%), storage modulus, glass transition temperature and adhesive strength were measured with respect to aliphatic/aromatic diisocyanate contents. The adhesive strength was maximum using mixed diisocyanates containing 25 mol% MDI in WBPU adhesives.

The Effect of Silicate Layers on Electrochemical Properties in Nanocomposite Solid Polymer Electrolytes

Nanocomposite solid polymer electrolytes (NSPEs) based on poly (vinylidene fluoride) (PVDF) were prepared by dispersing organically modified clay (Cloisite®30B, C30B) consisted of silicate layers in the polymer matrix. And ion conductive properties were investigated in relation to dispersed condition of silicate layers and structural changes of nanocomposites. The characterizations of PVDF/C30B nanocomposites with various C30B contents were analyzed by XRD, DSC, DMA and SEM. In order to confirm the ion conductive properties of NSPEs added to lithium trifluoromethansulfonate (LiCF3SO3) at room temperature, ac impedance analyzer and FT-IR spectrometer were used in this study. The degree of C30B dispersion in PVDF and the degree of crystallinity of PVDF/C30B nanocomposites showed the decrease with C30B contents. As a result, high ionic conductivity was observed in the sample added to 3wt% clay in the polymer matrix and the maximum conductivity was 9x10-4S/cm.

Synthesis of Poly(methylene oxy-alt PPO)glycols and Its Effect on the Properties of Polyurethane UV-Cured Film

In this study, we synthesized MPPG including the methylene-oxy group from polypropylene glycol (PPG) with the molecular weight (g/mol) of 200. Also UV curable resins were prepared from the mixture of polyurethane acrylate (PUA) oligomer which was synthesized with synthesized MPPG, TMPTA, HDDA, and HP-8 to investigate the possibility of its application for optical film materials. The Tg was higher for UAMP oligomer with MPPG as well as MPPG than that of PPG and UAP oligomer. The refractive index and the pencil hardness of UCM were higher than those of UC while the optical transmittances of UCM and UC were much the same.

Actuative Properties of CP Actuator Consisting of Polypyrrole Film and Solid Polymer Electrolyte

Conducting polymer (CP) actuators undergo volumetric changes due to the movement of dopant ions into the film during the electrical oxidation process. However, it may be an impediment for practical use of polypyrrole actuator that polypyrrole usually requires electrolyte solution for actuation. To solve this problem, solid polymer electrolyte(SPE) was introduced in CP actuator instead of electrolyte solution. And PPy/SPE/PPy electroactive tri-layer actuator was prepared by the electrochemical polymerization of pyrrole and the actuation characteristics were studied. An all-solid actuator, consisting of two polypyrrole films and a solid polymer electrolyte based on polyurethane, clearly showed a reversible displacement in an atmosphere when a voltage was applied.

The Effect of Hydrophilic Components of Zinc Based Copolymer on its Self Polishing Behavior

The zinc methacrylate copolymers with various monomer compositions were prepared for investigating the effects of zinc methacrylate, 2-methoxyethyl acrylate contents on self polishing behavior. The effect of molecular weight of the self polishing copolymer(SPC) was also investigated. The characterizations of copolymers were performed by fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry. The leaching rate of SPC was determined from the reduction of dry film thickness after seawater immersion in a dynamic condition. The experimental results revealed that leaching rate and mechanical property of the film could be controlled by the hydrophilic monomer composition of zinc based copolymer.