• 한국응용과학기술학회지
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• 제18권2호
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• pp.118-126
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• 2001

Micelle formation and adsorption at the $Ti0_{2}$ interface of a series of polystyrene-polythylene oxide(PS-PEO) block copolymer in aqueous solution was studied using fluorescence probing and small-angle X-ray methods. Further, the stability of aqueous $Ti0_{2}$ dispersion in the presence of copolymer was investigated by microelectrophoresis, optical density and sedimentation measurements. The dissolution of pyrene as fluorescent probe in aqueous surfactant solution leads to a slow decrease of the $I_{1}/I_{3}$ ratio, as the copolymer concentration increase; $I_{1}$ and $I_{3}$ are respectively the intensities of the first and third vibrionic peaks in the pyrene fluorescence emission. The behaviour was due to the characteristics of the copolymers and/or to the copolymer association efficiency in water. Moreover, the adsorption at the plateau level increases with decreasing PEO until chain length. The zeta potential of $TiO_{2}$ particles decreases with increasing copolymer concentration and reaches a plateau value. Finally, stabilization using block copolymers was more effective with samples having higher weight fractions of PS block.

• Korea-Australia Rheology Journal
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• 제13권2호
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• pp.83-87
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• 2001

The morphology and mechanical properties of the blends of a syndiotactic polystyrene (SPS) and poly-styrene-block-poly(ethylene-co-butylene)-block-polystyrene copolymers (SEBS) with various polystyrene block contents are studied. Mechanical properties, especially elongation at break and impact strength (IS), of the blend depend upon the morphology and interfacial adhesion, which in rum are affected by the viscosity ratio of constituent components and the styrene block content in SEBS. The IS of a blend was affected by the combined effect of rubber content and the interfacial adhesion. A maximum IS was found for a blend with the weight fraction of the PS block in an SEBS of 0.18. The IS of blends with smaller weight fractions of the PS block exhibited lower due to poor interfacial adhesion between SPS/SEBS in spite of a larger amount of rubber block. On the other hand, the IS of blends with larger weight fraction of the PS block becomes smaller due to lower amounts of rubber block in spite of better interfacial adhesion.

• 폴리머
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• 제32권2호
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• pp.143-149
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• 2008

생체적합성을 가진 친수성 poly(ethylene glycol)(PEG)블록과 생분해성 고분자인 Poly(D,L-lactide)(PLA) 또는 poly(lactide-co-glycolide)(PLGA)를 소수성 블록으로 하는 양친성 이중 블록공중합체를 합성하여 난용성 당뇨병 치료제인 pioglitazone의 가용화를 위한 고분자 미셀을 제조하였다. PEG 말단으로부터 LA의 개환중합에 의해 합성된 고분자의 화학적 조성과 분자량은 반응액 내 당량비로 조절하였고, 합성된 고분자는 수용액 상에서 $10{\sim}30\;nm$ 크기인 구형의 자기조립 미셀을 형성하였다($CMC=0.001{\sim}0.0076\;mg/mL$). 투석법과 고체분산법을 이용하여 약물을 봉입한 후 AFM, DLS, HPLC 분석을 통하여 미셀의 특성을 비교하였다. 결론적으로 PEG-PLA(또는 PLGA) 공중합체를 이용한 고체분산법을 통해 pioglitazone을 효과적으로 가용화시킬 수 있었다.

• 한국막학회:학술대회논문집
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• 한국막학회 1997년도 추계 총회 및 학술발표회
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• pp.69-70
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• 1997

Polyimides and related polymers, when synthesized from aromatic monomers, have generally rigid chain structures resulting in a low gas permeability. The rigidity of polymer chains reduces the segmental motion of chains and works as a good barrier against gas transport. To overcome the limit of use as materials of gas separation membranes due to low gas permeability, block copolymers with the incorporation of flexible segments like siloxane linkage and ether linkage have been studied. These block copolymers have microphase-separated structures composed of microdomains of flexible poly(dimethylsiloxane) or polyether segments and of rigid polyimides segments. In case of rigid-flexible block copolymers, the characteristics of both phases for gas permeation are of great difference. The permeation of gas molecules occurs favorably through microdomains of flexible segments, whereas those of rigid segments hinder the permeation of gas molecules. Accordingly the increase of content of flexible segments in a rigid polymer matrix will increase the gas permeability of the membrane linearly. However, this prediction does not satisfy enough many experimental results and in particular the drastic increase of the permeability is observed in a certain volume fraction. It was proposed that the gas transport mechanism is dominated by diffusion rather than gas solubility in a certain content of flexible phase if solution-diffusion mechanism is adopted. However, the transition from solubility-dependent to diffusion-dependent cannot be explained by the understanding of mechanism itself. Therefore, we consider an effective chemical path which permeable phase can form in a microheterogenous medium, and percolation concept is introduced to describe the permeability transition at near threshold where for the first time a percolation path occurs. The volume fraction of both phases is defined as V$_{\alpha}$ and V$_{\beta}$ in block copolymers, and the volume of $\beta$ phase in the threshold forming geometrically a traversing channel is defined as V$_{\betac}$. The formation mechanism of shortest chemical channel is schematically depicted in Fig. 1.

• 폴리머
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• 제38권1호
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• pp.9-15
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• 2014

Methylene diphenyl diisocyanate(MDI)와 poly(tetramethylene glycol)(PTMG)로부터 양말단에 isocyanate(NCO) 작용기를 가진 polyurethane(PU) prepolymer를 제조한 다음 이를 개시제로 하고 potassium pyrrolidonate를 촉매로 하여 2-pyrrolidone을 음이온 개환중합함으로써 최종적으로 양 끝에 polyamide4(PA4)가 단단한 블록이 되고 PU가 부드러운 블록이 되는 PA4-PU-PA4 형태의 삼블록 공중합체를 합성하였다. 그리고 공중합체내 각각 PA4 블록과 PU 블록의 분자량을 변화시켜 이들의 변화가 여러 가지 성질에 미치는 영향을 확인하였다. 결과적으로 PA4 블록으로 인해 원래의 PU 탄성체보다 용융온도($T_m$)는 크게 상승하였고 PA4 블록의 분자량이 증가함에 따라 초기 탄성률과 인장강도는 크게 증가하였다. 한편, PU 블록의 분자량이 증가되면 파단신율이 증가하였지만 초기 탄성률과 인장강도는 감소하는 전형적인 블록 공중합체형 탄성체의 성질을 나타냈다.

• Bulletin of the Korean Chemical Society
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• 제23권6호
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• pp.872-879
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• 2002

One of the improtant characteristics of core-shell type nanoparticles is the long-term storage and reuse as an aqueous injection solution when required. For this reason, reconstruction of lyophilized core-shell type nanoparticles is considered to be essential . BAB type triblock copolymers differ from AB type diblock copolymers, which contain the A block as a hydrophilic part and the B block as a hydrophobic part. by not being easily redistributed into phosphate-buffered saline (PBS, pH 7.4, 0.1 M). Therefore, lyophilized core-shell type nanoparticles of CEC triblock copolymer were reconstituted using a somication process with a bar-type sonicator in combination with a freezing-thawing process. Soncation for 30s only resuspended CEC nanoparticles in PBS; their particle size distribution showed a monomodal pattern with narrow size distribution. The bimodal size distribution pattern and the aggregates were reduced by further sonication for 120 s but these nanoparticles showed a wide size distribution. The initial burst of drug release was increased by reconstitution process. The reconstitution of CEC core-shell type nanoparticles by freezing-thawing resulted in trimodal distribution pattern and formed aggregates, although freezing-thawing process was easier than sonication . Drug release form CEC nanoparticles prepared by freezing-thawing was slower than from the original dialysis solution. Although core-shell typenanoparticles of CEC triblock copolymers were not easily performed. Cytotoxicity testing of core-shell type nanoparticles of CEC-2 triblock copolymers containing clonazepam (CNZ) was performed using L929 cells. Cytotoxicity of CNZ was decreased by incorporation into nanoparticles.

• 공업화학
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• 제4권2호
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• pp.349-357
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• 1993

Hydroxy-difunctional polyarylate(PAR) 올리고머와 toluene diisocyanate를 반응시켜 합성한 고분자 활성체를 사용하여 ${\varepsilon}$-caprolactam을 음이온 중합하여 다양한 블록길이의 PAR-nylon 6 블록공중합체들을 합성하였다. 합성한 블록공중합체들의 열적성질을 differential scanning calorimeter(d.s.c.)로 측정한 결과, 블록공중합체를 구성하는 PAR 블록과 nylon 6 블록은 부분적 상용성을 가졌으며, 그 정도는 블록의 길이가 짧을수록 컸다. PAR-nylon 6 블록공중합체와 PAR 혹은 nylon 6 homopolymer와의 이원블렌드에서 PAR homopolymer와 PAR 블록, nylon 6 homopolymer와 nylon 6 블록 사이의 분자수준의 섞임을 시사하는 거동을 d.s.c.로 관찰할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2377-2384
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• 2011

Azo-acenaphthylene oligomers with repeating acenaphthylene units "n" up to 4, 5, 7, 17 and 19 have been prepared successfully using nitroxide mediated Stable Free Radical Polymerization (SFRP). Azo-acenaphthylene oligomers, reversibly end-capped by the stable nitroxide 2,2,6,6-tetramethyl-1-piperidinoxyl (TEMPO), were further reacted via radical addition to 4-(naphthalenemethoxy)styrene monomer for diblock co-polymer formation. Characterization of the oligomers and diblock co-polymers was accomplished using MALDI-MS supported by GPC (Gel Permeation Chromatography) and $^1H$ NMR spectrometry. MALDI-MS afforded definitive results by providing an inter-peak interval of 152 (m/z), corresponding to acenaphthylene monomer, and inter-peak interval of 260 (m/z) for the naphthalenemethoxystyrene monomer unit in block copolymers. Our study opens the way to control the number of repeat units in the oligomers. Further these oligomers can be tailored with various monomers for the formation of block copolymers.

• 한국막학회:학술대회논문집
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• 한국막학회 1998년도 춘계 총회 및 학술발표회
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• pp.83-86
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• 1998

1. Introduction : Low molecular harmful organics such as 1-naphthol and phenol are widely used in industries, and pose serious environmental problems. Wastewater containing low molecular harmful organics may be ejected from various sources including metal-plating industries, circuit-board manufacturing process, photographic and photo-processing industries, refineries and metal-tailing leachate. The pollution of nation harbors, waterways and ground water resources with these organics has reached critical portions, and might also give hazardous influence on human health. Micellar enhanced ultrafiltration(MEUF) is a recently developed process to remove dissolved organics and/or heavy metals present in small or trace quantities from aqueous solution. In this system, the fatal defect is leakage of surfactants especially at low concentration below CMC(critical micelle concentration), which becomes a secondary pollution. Our group proposed to use biosurfactant and polymeric micelle to solve problems mentioned above. In this study we investigated a modified MEUF using PEO-PPO-PEO (polyethyleneoxide-polypropyleneoxide-polyethyleneoxide) block copolymers for the removal of organic solutes such as 1-naphthol and phenol from aqueous wastewater. We proposed PEO-PPO-PEO block copolymers as new surfactants for forming micelles in MEUF, and investigated the solubilization characteristics and efficiency for the removal of 1-naphthol and phenol. PEO-PPO-PEO block copolymers are, environmentally mild and safe as biosurfactants.

• Macromolecular Research
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• 제13권4호
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• pp.344-351
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• 2005

pH-sensitive block copolymers were synthesized by coupling reaction of sulfamethazine and amphiphilic diblock copolymer, and their micellization-demicellization behavior was investigated. Sulfamethazine (SM), a derivative of sulfonamide, was introduced as a pH responsive moiety while methoxy poly(ethylene glycol)poly(D,L-lactide) (MPEG-PDLLA) and methoxy poly(ethylene glycol)-poly($D,L-lactide-co-{\varepsilon}-caprolactone$) (MPEG-PCLA) were used as biodegradable amphiphilic diblock copolymers. After the sulfamethazine was carboxylated by the reaction with succinic anhydride, the diblock copolymer was conjugated with sulfamethazine by coupling reaction in the presence of DCC. The critical micelle concentration (CMC) and mean diameter of the micelles were examined at various pH conditions through fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. For MPEG-PDLLA-SM and MPEG-PCLA-SM solutions, the pH-dependent micellization-demicellization was achieved within a narrow pH band, which was not observed in the MPEG-PDLLA and MPEG-PCLA solutions. The micelle showed a spherical morphology and had a very narrow size distribution. This pH-sensitive block copolymer shows potential as a site-targeted drug carrier.