• Proceedings of the Korean Society of Sericultural Science Conference
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• 1997.06a
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• pp.159-169
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• 1997

ABA-type(or AB) block copolymers composed of poly(${\gamma}$-alkyl L-glutamate) (PALG)[or poly(L-leucine)] as the A component and polyether[or poly (N-isopropy1 acrylamide) as the B component were synthesized by polymerization of (${\gamma}$-alkyl L-glutamate N-carboxyanhydride initiated by primary amined located at both(or one) ends of the polymer chains. Structural studies of the block copolymers were performed in the solution and solid state. Also, artificial skin, drug delivery system of the block copolymers and cell attachment onto the copolymer were carried out for biomedical applications.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.101-101
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• 2006

We have studied the micellisation of poly(n-butyl acrylate)-block-poly(acrylic acid) and poly(n-butyl acrylate)-graft-poly(acrylic acid) in aqueous solution. The size and structure of the formed micelles was elucidated by scattering and imaging techniques. The micelle structure depends on pH, composition, and topology: graft copolymers form much smaller micelles that block copolymers of similar composition. We have also synthesized block copolymers of acrylic acid and N-isopropylacrylamide (NIPAAm) or N,N-diethylacrylamide (DEAAm). Due to the LCST of polyNIPAAm and polyDEAAm, these block copolymers spontaneously form micelles upon heating and they form inverse micelles upon decreasing pH below 4. If the LCST block is much longer than the PAA one, this presents a very convenient way to prepare crew-cut micelles. The polymers have been successfully used as stabilizers in emulsion polymerization. They also have been conjugated to streptavidin. The conjugates reversibly form mesoscopic particles on heating.

• Macromolecular Research
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• v.16 no.4
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• pp.267-292
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• 2008

Block copolymers that two or more polymer chains are covalently linked have drawn much attention due to self-assembly into nanometer-sized morphology such as lamellae, cylinders, spheres, and gyroids. In this article, we first summarize the phase behavior of block copolymers in bulk and thin films and some applications for new functional nanomaterials. Then, future perspectives on block copolymers are described.

• Macromolecular Research
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• v.17 no.6
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• pp.365-377
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• 2009

In this feature article, we briefly review the new methods we have utilized recently in the investigation of morphology and phase behavior of block copolymers. We first describe the chromatographic fractionation method to purify block copolymers from their side products of mainly homopolymers or block copolymer precursors inadvertently terminated upon addition of the next monomer in the sequential anionic polymerization. The chromatographic method is extended to the fractionation of the individual block of diblock copolymers which can yield the diblock copolymer fractions of different composition and molecular weight, which also have narrower distributions in both molecular weight and composition. A more detailed phase diagram could be constructed from the set of block copolymer fractions without the need of acquiring many block copolymers each prepared by anionic polymerization. The fractions with narrow distribution in both molecular weight and composition exhibit better long-range ordering and sharper phase transition. Next, epitaxial relationships between two ordered structures in block copolymer thin film is discussed. We employed the direct visualization method, transmission electron microtomography(TEMT) to scrutinize the grain boundary structure.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.74-75
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• 2006

In organic opto-electronic applications, such as light emitting diodes (LEDs) and photovoltaic devices (PVDs), the morphology of the active layer is of crucial importance. To control the morphology of the active layer the self-assembling properties of block copolymers was used. Several rod-coil semiconducting diblock copolymers consisting of a conjugated block and a second coil block functionalized with electron transporting and/or accepting materials (such as $C_{60}$) were synthesized. The conjugated block acting as light absorbing, electron donating and hole transporting material. The donor/acceptor photovoltaic devices performance with active layer the above mentioned semiconducting block copolymers will be presented.

• Macromolecular Research
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• v.14 no.4
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• pp.424-429
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• 2006

The synthesis of a series of poly(POSS-NBE-b-MTD) copolymers was successfully accomplished, taking advantage of sequential, ring-opening, metathesis block copolymerization using $RuCl_2(=CHPh)(PCy_3)_2$ catalyst. By using cyclopentyl-POSS-norbornene (POSS-NBE) monomer as the first block in the block copolymer, living poly(POSS-NBE) with controlled molecular weight and narrow molecular weight distribution was produced. Then, poly(POSS-NBE-b-MTD) copolymers were successfully prepared, in which sequential monomer addition of methyltetracyclododecene (MTD) to the living poly(POSS-NBE) chain ends was utilized to achieve quantitative crossover efficiency. Characterization by $^1H$ NMR spectroscopy and GPC confirmed the high definition and structural integrity of the poly(PO$S-NBE-b-MTD) copolymers. Thermal properties-and morphologies of the POSS-containing block copolymer nanocomposites were also investigated by using thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and wide-angle X-ray scattering (WAXS).

• Macromolecular Research
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• v.10 no.2
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• pp.85-90
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• 2002

Poly (ethylene oxide)/polylatide/poly(ethylene oxide) (PEO/PL/PEO) tri-block copolymers, which each block is connected by ester bond, were synthesized by coupling reaction of PL with PEO in the presence of pyridine. PL/PEO/PL tri-block copolymer was synthesized by ring opening polymerization of L-lactide initiated by PEO in the presence of stannous octoate. Degradation behavior of the copolymers was investigated in a pH 7.4 phosphate buffer saline (PBS) at 37$\pm$1 $^{\circ}C$. Gel permeation chromatography (GPC) and $^1$H-nuclear magnetic resonance (NMR) were used to monitor the change of mass loss, molecular weight and composition of copolymers. In hydrolytic degradation, the PEO/PL/PEO tri-block copolymer with high PEO contents affected the increase of its mass loss, and resulted in the decrease of its molecular weight as well as PEO composition. However, when PL/PEO/PL and PEO/PL/PEO tri-block copolymers had similar PEO contents, PEO/PL/PEO decreased faster in molecular weight and PEO composition than PL/PEO/PL.

• Fibers and Polymers
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• v.4 no.1
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• pp.15-19
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• 2003

The self-assembly of asymmetric ABC triblock copolymers in the ordered structure is investigated using an isothermal-isobaric molecular dynamics simulation. Unlike symmetric A BC triblock copolymers, more fascinating mophologies are observed in asymmetric ones because of a larger difference of incompatibility between the components. Various modes of self-assembly in assymmetric ABC triblock copolymers are also observed depending on the block composition. When the composition of block A Is changed from 0.125: to 0.25 at the same $f_B$ : 0.25, the morphological transition from the “cylinder in cylinder” to “cylinders at cylinder” structure is observed in the simulation. In the case of ABC triblocks with $f_B$=0.5, a lamellar-type structure is changed to a cylinder-type structure with increasing the length of block A. When the midblock length increases further to $f_B$=0.625, the “spheres on cylinder” structure is observed in both the $A_{10}$$B_{50}$$C_{20}$ and $A_{20}$$B_{50}$$C_{10}$ triblocks. From these results, the phase diagram of ABC triblock copolymers can be constructed.

• Polymer(Korea)
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• v.24 no.5
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• pp.638-645
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• 2000

Linear and star-shaped, poly(lactic acid) (PLA) stereo-block copolymers were synthesized by sequential polymerization of DL-lactic acid and L-lactide in the presence of diol or polyol compounds. The molecular weight of block copolymers could be controlled to some extent by the variation of alcohol content. These block copolymers had relatively narrow molecular weight distributions. The glass transition temperature and melting temperature of block copolymers appeared at around 5$0^{\circ}C$ and 100~14$0^{\circ}C$, respectively. The block copolymers were found to crystallize even at the high D-stereoisomer concentration of 35 mol%, in contrast to the amorphous nature of the random copolymer with similar composition. Also we could observe the crystallinity of PLA stereo-block copolymers varying with annealing temperature and time.

• Journal of Radiation Industry
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• v.6 no.2
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• pp.171-176
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• 2012

In this study, a crosslinked poly(styrene-butadiene-styrene) [SBS] block copolymers were prepared by using gamma ray irradiation method. The effects of various radiation doses on the degree of crosslinking, thermo property, and morphology of crosslinked SBS block copolymer were investigated. The degree of crosslinking of crosslinked SBS block copolymers were measured by gel-fraction and FT-IR. It was found that the degree of crosslinking of crosslinked SBS block copolymers increases with increase of the irradiation dose while the TGA result shows that the initial degradation temperature of irradiated SBS block copolymer was shifted to lower temperature with increasing irradiation dose. These results indicate that degradation reaction also occurs when SBS block copolymer is exposed to gamma ray irradiation for crosslinking reaction. The SAXS and FE-SEM results indicate that the phase separation of the styrene block and butadiene block was reduced with increasing irradiation dose.