• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.191-191
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• 2006

The structures of the mesophases and their subunits of PS-b-P4VP in a toluene solution were studied by using SAXS, TEM and GIFT methods. The hierarchical structures of PS-b-P4VP, such as the individual micelle, the face-centered cubic (fcc) and body-centered cubic (bcc) structures and the lamellar structure, were identified for the first time. The diameter of the micelle core was ${\sim}80\;%$ of the most extended chain length of the core chain, suggesting that the core chains were quite stretched. The stretched chain in the core caused the core of the micelle to be not homogenous with a higher density at the center than at the outer part. As the concentration level increases, the fcc and both fcc and bcc appear for the packing of the micelles of PS(3.3k)-b-P4VP(4.7K) and PS(12K)-b-P4VP(11.8K), respectively. The lamellar structure was also identified, with a further increase in the concentration for PS(3.3k)-b-P4VP(4.7K). These hierarchical structures were also identified via TEM images.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.81-90
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• 2010

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with antireflective properties. Protonated polystyrene-block-poly (4-vinylpyrine) (PS-b-P4VP) and anionic polystyrene-block-poly (acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the oppositely BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. Furthermore, we demonstrate that the nanostructured electrochemical sensors based on patterning methods show the electrochemical activities. Anionic poly(styrene sulfonate) (PSS) layers were selectively and uniformly deposited onto the catalase (CAT)-coated surface using the micro-contact printing method. The pH-induced charge reversal of catalase can provide the selective deposition of consecutive PE multilayers onto patterned PSS layers by causing the electrostatic repulsion between next PE layer and catalase. Based on this patterning method, the hybrid patterned multilayers composed of platinum nanoparticles (PtNP) and catalase were prepared and then their electrochemical properties were investigated from sensing $H_2O_2$ and NO gas. This study was based on the papers reported by our group. (J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007)).

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.214-219
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• 2017

In this work, we fabricated PS-b-P4VP block copolymer membranes from self-assembly and non-solvent induced phase separation (SNIPS), which combines the block copolymer self-assembly and conventional NIPS process. While previous studies mostly focused on the fabrication of well-defined structures, we systematically examined various processing parameters such as polymer concentration, solvent evaporation duration, solvent composition, and humidity, to optimized the membrane structures. As a result, the morphology of PS-b-P4VP membranes was optimized at a certain polymer concentration in solution and composition of volatile solvent at low humidity conditions, resulting in SNIPS separation membranes with well-defined nanopores on the surface, 75% of membrane porosity, and 18% of surface porosity.

• Macromolecular Research
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• v.17 no.8
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• pp.553-556
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• 2009

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1B
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• pp.201-208
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• 2000

In the transmitter of optical communication systems, a time-division multiplexer combines several parallel data streams into a single data stream with a high bit rate. In this paper, we design a 4:1 (4-channels) time-division multiplexer using SiGe HBT with emitter size of 2x8um2. The operation speed is 100bps, the rise and fall times of 20-80% are 34ps and 34ps, respectively and the dissipation of power is 1.50W.

• Polymer(Korea)
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• v.32 no.5
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• pp.465-469
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• 2008

Hybrid thin films composed of block copolymer(BCP) and $TiO_2$ with various morphologies on the nanoscale were fabricated using self-assembly of block copolymer combined with sol-gel process. The factors governing morphology changes considered in this study are block copolymer composition, selectivity of solvent and the inclusion of an additive. We also investigated the efficiency of photoluminescence for selected films with different morphologies. Micelle or nanowire structure can be derived from the self-assembly of poly (styrene-block-4-vinyl pyridine) (PS-b-P4VP) depending on the relative selectivity of the solvent for the two blocks, and the titanium tetraisopropoxide ($Ti{OCH (CH_3)_2}_4$, TTIP) is coordinated with nitrogen in P4VP block. Addition of a third component 3-pentadecylphenol into the BCP/sol-gel mixture solution induces morphology change as a result of the change of relative volume fraction of the BCP. We confirmed that the efficiency of $TiO_2$ fluorescence changes for films depending on morphologies.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.618-624
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• 2013

We demonstrated unique inter- and intra-plasmonic coupling effects in bimetallic Au@Ag core-shell NP arrays which are regularly or randomly arranged on self-assembled block copolymer (BCP) inverse micelle monolayers. Polyvinylpyrrolidone (PVP)-stabilized Au@Ag core-shell NP arrays in regular or disordered configuration were incorporated and assembled on reconstructed PS-b-P4VP inverse micelle templates through two types of processes. The intensively enhanced LSPR coupling properties of individual and assembled Au@Ag NPs were evaluated by UV-visible spectroscopy in terms of the type of ligand stabilizer, coupling between Au and Ag, thickness of Ag shell, and type of array configuration. Finally, Au@Ag core-shell NP arrays were employed as active substrates for surface enhanced Raman spectroscopy (SERS) and a significantly enhanced signal enhancement was observed in accordance with the coupling intensity of Au@Ag NPs patterns.