• Korean Journal of Materials Research
• /
• v.28 no.12
• /
• pp.685-690
• /
• 2018

In this study, a multifunctional ophthalmic lens material with an electromagnetic shielding effect, high oxygen permeability, and high water content is tested, and its applicability is evaluated. Metal oxide nanoparticles are applied to the ophthalmic lens material for vision correction to shield harmful electromagnetic waves; the pyridine group is used to improve the antibacterial effect; and silicone substituted with urethane and acrylate is employed to increase the oxygen permeability and water content. In addition, multifunctional tinted ophthalmic lens materials are studied using lens materials with an excellent antibacterial effect (2,6-difluoropyridine, 2-fluoro-4-pyridinecarboxylic acid) and functional (UV protection, high wettability) lens materials (2,4-dihydroxy benzophenone, 2-hydroxy-4-(methacryloyloxy)benzophenone). To solve problems such as air bubbles generated during the polymerization process for the manufacturing and turbidity of the lens surface, polymerization conditions in which the defect rate is minimized are determined. The results show that the polymerization temperature and time are most appropriate when they are $110^{\circ}C$ and 40 minutes, respectively. The optimum injection amount of the polymerization solution is 350 ms. The turbid phenomenon that appears in lens processing is improved by 10 to 95 % according to the test time and conditions.

• Elastomers and Composites
• /
• v.46 no.1
• /
• pp.60-69
• /
• 2011

The various types of PBA/PMMA composite latexes were prepared by $2.1\;{\mu}m$ PBA seeded batch and seeded semi-continuous dispersion polymerization. The morphology of the PBA/PMMA composite latexes by seeded batch process was found to be closely dependant on the weight ratios of methanol/water in polymerization medium and of PBA seed/MMA at the second stage. In general, egg, snowman, confetti, peanut-like nonspherical composite latex particles were formed with increasing amount of water and MMA as a result of the occurrence of the phase separation between PBA seed and PMMA. The morphology of the PBA/PMMA composite latexes by seeded semi-continuous process was controlled by the addition time of MMA, especially, spherical shaped core(PBA)/shell(PMMA) composite latex particles were prepared under the monomer-starved condition at the second stage.

• Elastomers and Composites
• /
• v.44 no.1
• /
• pp.55-62
• /
• 2009

In this study, investigation on the polymerization characteristics of isoprene through nitroxide mediated controlled/"living" radical polymerization techniques was attempted. In the presence of acetol, linear increase of isoprene conversion with time and low polydispersities of the resulting polymers ($M_w/M_n$ < 1.5) were observed, which suggest successful controlled/"living" radical polymerization of isoprene. The microstructure of the resulting polyisoprene was composed of $\sim$ 22% of 3, 4, $\sim$30% of 1, 4-cis and $\sim$ 48% of 1, 4-trans. The optimum polymerization temperature was 145 $^{circ}C$, below which no significant polymerization behavior was observed. Non-cyclic nitroxide, such as di-tert-butyl nitroxide (DTBN) could not mediate the polymerization, whereas cyclic nitroxides (2, 2, 6, 6-tetramethyl-1-peperidine 1-oxyl (TEMPO) and 4-oxo-2, 2, 6, 6-tetramethyl-1-peperidine 1-oxyl (oxoTEMPO)) were successfully employed for the polymerization. However, isoprene dimerization reaction through Diels-Alder process was also observed at the given polymerization condition, which afforded a significant amount of limonene. Isoprene thermal autoinitiation was also possible, which was, however, considered to be not significant under the given polymerization condition.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.418-418
• /
• 2012

We fabricated a new type of hybrid film using molecular layer deposition (MLD). The MLD is a gas phase process analogous to atomic layer deposition (ALD) and also relies on a saturated surface reaction sequentially which results in the formation of a monolayer in each sequence. In the MLD process, polydiacetylene (PDA) layers were grown by repeated sequential surface reactions of titanium tetrachloride and 2,4-hexadiyne-1,6-diol with ultraviolet (UV) polymerization under a substrate temperature of $100^{\circ}C$. Ellipsometry analysis showed a self-limiting surface reaction process and linear growth of the hybrid films. Polymerization of the hybrid films was confirmed by infrared (IR) spectroscopy and UV-Vis spectroscopy. Composition of the films was confirmed by IR spectroscopy and X-ray photoelectron (XP) spectroscopy. The titanium oxide cross-linked polydiacetylene (TiOPDA) hybrid films exhibited good thermal and mechanical stabilities.

• Polymer(Korea)
• /
• v.29 no.4
• /
• pp.418-421
• /
• 2005

Three-dimensional (3D) microfabrication process using two-photon polymerization (TPP) is developed to fabricate the curved microstructures in a layer, which can be applied potentially to optical MEMS, nano/micro-devices, etc. A 3D curved structure can be expressed using the same height-contours that are defined by symbolic colors which consist of 14 colors. Then, the designed bitmap figure is transformed into a multi-exposure voxel matrix (MVM). In this work a multi-exposure voxel matrix scanning method is used to generate various heights of voxels according to each laser exposure time that is assigned to the symbolic colors. An objective lens with a numerical aperture of 1.25 is employed to enlarge the variation of a voxel height in the range of 1.2 to 6.4 um which can be controlled easily using the various exposure time. Though this work some 3D curved micro-shapes are fabricated directly to demonstrate the usefulness of the process without a laminating process that is generally required in a micro-stereolithography process.

• Polymer Science and Technology
• /
• v.7 no.4
• /
• pp.384-396
• /
• 1996

• Polymer Science and Technology
• /
• v.4 no.3
• /
• pp.179-188
• /
• 1993

• Polymer Science and Technology
• /
• v.6 no.5
• /
• pp.499-508
• /
• 1995

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.320-320
• /
• 2006

The authors report the synthesis and radical ring-crossover polymerization of macrocycles with radically exchangeable dynamic covalent bonds. The macrocyclic compounds with alkoxyamine units were designed and synthesized by condensation from alkoxyamine-based diol and the corresponding acid chlorides in the presence of pyridine under high-dilution condition. The macrocycles can thermally polymerize by intermolecular radical crossover reaction. Furthermore, the poly(alkoxyamine)s depolymerized to the monomers principally by the intramolecular radical exchange process under high-dilution conditions.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.6 no.5
• /
• pp.697-702
• /
• 2011

In this paper, We have fabricated PMMA thin films by plasma polymerization method for organic thin film transistor's insulator layer. In the electrical characteristic results with deposition pressures and substrate RF bias power in thin film deposition process, we have got dielectric constant of 3.4, high deposition rate of 8.6 [nm/min] and high insulation characteristics in condition of RF100 [W], Ar20 [sccm], 5 [mtorr], RF bias 20 [W]. Therefore, the fabricated thin films are possible as insulation layer of OTFT and organic memory.