• Macromolecular Research
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• 제12권4호
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• pp.379-383
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• 2004

Poly(ethylene glycol)s (PEGs) are unique in their material properties, such as biocompatibility, non-toxicity, and water-solublizing ability, which are extremely useful for a variety of biomedical applications. In addition, a variety of functional PEGs with specific functionality at one or both chain ends have been synthesized for many specialized applications. Surface modifications using PEG have been demonstrated to decrease protein adsorption and platelet or cell adhesion on biomaterials. Furthermore, PEGs having anionic sulfonate terminal units have been proven to enhance the blood compatibility of materials, which has been demonstrated by the negative cilia concept. The preparation of telechelic PEGs having a sulfonic acid group at one end and a polymerizable methacryloyl group at the other is an interesting undertaking for providing macromers that can be used in various vinyl copolymerization and gel systems. In this paper, preliminary results on the synthesis and polymerization behavior of a novel PEG macromer is described with the aim of identifying a biocompatible material for applications in various blood-contacting devices.

• Macromolecular Research
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• 제14권5호
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• pp.545-551
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• 2006

Aqueous dispersions of pristine and functionalized (COOH- and $NH_2$-) multi-walled, carbon nanotubes (MWNTs) were prepared by using three types of surf act ants: sodium dodecyl sulfate (SDS, anionic), PEO-PPO-PEO (Pluronic P84, non-ionic), and poly(styrene/$\alpha-methyl$ styrene/acrylic acid) random terpolymer, i.e., alkali-soluble resin (ASR). The aggregate size, $\zeta-potential$, and storage stability of the MWNT aqueous dispersions were investigated by using dynamic light scattering and the turbidity method at room temperature. The exfoliation of the MWNT aggregates was determined by a UV-visible spectrophotometer and the morphology of the surfactant-coated MWNTs was observed by transmission electron microscopy (TEM). In all cases, ASR showed better dispersion stability with the smallest aggregate size, compared with the other surfactants, because of its unique molecular structure, i.e., randomly incorporated carboxylic acid groups and planar phenyl groups that can be irreversibly and effectively adsorbed on the MWNT surface. A predominantly-exfoliated morphology of MWNTs was observed in the presence of ASR from the strong intensity of the UV-vis spectrum at 263 nm.

• 펄프종이기술
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• 제37권1호
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• pp.1-9
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• 2005

Many factors which affect the adsorption of cationic polymers on fibers and fines have been investigated by many researchers that include contact time, pH, collision frequency, properties of cationic polymers and adsorbent, etc. But the effect of white water quality on the adsorption of cationic polymer have not been examined throughly. In this study, the adsorption of cationic PAM was analyzed as a function of white water quality. The adsorption of the cationic PAM was analyzed by two analysis methods, Kjeldahl nitrogen content measurement and electrokinetic measurements. When the distilled water was used, adsorbed amount of C-PAM and zeta-potential of fibers increased as a function of the addition of C-PAM. When closure level increased, nitrogen content of fibers increased indicating that the cationic PAM was adsorbed. Zeta-potential of fibers, however, showed no significant change with the increased addition of C-PAM. This showed that adsorption of C-PAM was not reflected by zeta-potential of fibers due to the deteriorated efficiency of C-PAM by the anionic contaminants in white water.

• 멤브레인
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• 제9권1호
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• pp.10-16
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• 1999

본 연구에서는 pellet 상태의 polyetherimide (PEI)를 carbon tetrachloride(CCl4)와 1 ,2-dichloro-ethane (DCE) 의 부피비 5:1 하에서 PEI를 불균일한 상태로 유지시키고, chlorosulfonic acid (CSA)를 이용하여 PEI의 표면을 sulfonation 시킴으로써 , 음이온성을 띠며 친수성이 향상된 sulfonated polyetherimide (SPEI)를 제조하였다. 불균일한 상태가 유지되면서 가장 적합한 sulfonation 반응조건은 PEI: CSA 의 1 : 1 mole ratio, 온도 $10^{\circ}$, 3 시간이었다. 이온교환용량이 0.2~1.2meq/g을 갖는 SPEI를 합성할 수 있었고, FT-IR 측정을 통하여 sulfonic acid peak가 1020$cm^{-1}$ 와 1170$cm^{-1}$부근에서 관찰되었다. 분자량 분포는 sulfonation을 시킴으로써 좀 더 넓게 나타났고, 접촉각 측정을 통하여 친수성이 향상되었음을 확인하였다.

• Korea-Australia Rheology Journal
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• 제17권4호
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• pp.181-190
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• 2005

Rheological characterisation of flocculated kaolinite pulps has been undertaken to elucidate particle interactions underpinning the dewatering behaviour induced by flocculation with polyethylene oxide (PEO), anionic polyacrylamide (PAM A) and their blends. Shear yield stress $(\tau_y)$ analysis indicated that polymer mediated particle interactions were markedly amplified upon shear of PEG based pulps. In contrast, PAM A based pulps showed a significant decrease in yield values upon shear. Steady stress measurements analysed using a modified Ellis model indicated subtle differences between the respective linear viscoelastic plateaus of the pulps. Furthermore, modified shear thinning behaviour was evident in PEG based pulps. Estimation of elastic and viscous moduli (G', G') was made using dynamic stress analysis for comparison with values determined from vane measurements. Despite a noticeable difference in the magnitude of G' between the two methods, similar trends indicating sheared PEG-based pulps to be more elastic than PAM based pulps, were observed. Floc microstructural observations obtained in support of rheological properties indicate that PEG flocculant induces significantly more compact particle aggregation within the clay pulps under shear consistent with the yield stress data, in contrast to PAM A, or indeed unsheared PEG based pulps. Consequentially, sheared PEG based pulps show significantly improved dewatering behaviour. The implications of the results, potential benefits and drawbacks of flocculation with PEG and PAM A are discussed with respect to improvements in current dewatering processes used in the minerals industry.

• Journal of Microbiology and Biotechnology
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• 제28권12호
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• pp.2141-2144
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• 2018

Based on previous studies reporting the anti-prion activity of poly-${\text\tiny{L}}$-lysine and poly-${\text\tiny{L}}$-arginine, we investigated cationic poly-${\text\tiny{L}}$-ornithine (PLO), poly-${\text\tiny{L}}$-histidine (PLH), anionic poly-${\text\tiny{L}}$-glutamic acid (PLE) and uncharged poly-${\text\tiny{L}}$-threonine (PLT) in cultured cells chronically infected by prions to determine their anti-prion efficacy. While PLE and PLT did not alter the level of $PrP^{Sc}$, PLO and PLH exhibited potent $PrP^{Sc}$ inhibition in ScN2a cells. These results suggest that the anti-prion activity of poly-basic amino acids is correlated with the cationicity of their functional groups. Comparison of anti-prion activity of PLO and PLH proposes that the anti-prion activity of poly-basic amino acids is associated with their acidic cellular compartments.

• 공업화학
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• 제34권1호
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• pp.1-8
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• 2023

폴리에틸렌이민(polyethylenimine, PEI)은 양이온성 고분자로서 핵산(nucleic acid)와 같이 음전하를 띄는 생체 물질과 강한 정전기적 상호작용으로 결합할 수 있다. 이러한 특성을 바탕으로 PEI는 효율적인 약물전달체로 오랜 기간 활용되었다. 하지만 PEI의 강한 양이온성은 체내에서 음이온을 띄는 생체 물질과 비특이적으로 상호작용하여 세포독성을 띄는 문제점을 가지고 있다. 그 동안 많은 연구자들은 PEI의 단점을 극복하기 위하여 다양한 종류의 생체 적합 PEI 기반 물질을 개발하였다. 본 리뷰에서는 기능성 PEI의 개발과 이를 활용한 생의학적 연구 동향에 대하여 소개하고자 한다.

• Journal of Electrochemical Science and Technology
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• 제15권2호
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• pp.207-219
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• 2024

Metal-N-C (MNC) catalysts have been anticipated as promising candidates for oxygen reduction reaction (ORR) to achieve low-cost polymer electrolyte membrane fuel cells. The structure of the M-N_x moiety enabled a high catalytic activity that was not observed in previously reported transition metal nanoparticle-based catalysts. Despite progress in non-precious metal catalysts, the low density of active sites of MNCs, which resulted in lower single-cell performance than Pt/C, needs to be resolved for practical application. This review focused on the recent studies and methodologies aimed to overcome these limitations and develop an inexpensive catalyst with excellent activity and durability in an alkaline environment. It included the possibility of non-precious metals as active materials for ORR catalysts, starting from Co phthalocyanine as ORR catalyst and the development of methodologies (e.g., metal-coordinated N-containing polymers, metal-organic frameworks) to form active sites, M-N_x moieties. Thereafter, the motivation, procedures, and progress of the latest research on the design of catalyst morphology for improved mass transport ability and active site engineering that allowed the promoted ORR kinetics were discussed.

• 대한화학회지
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• 제32권6호
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• pp.593-602
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• 1988

크라운 에테르를 반복 사용 기능의 상이동 촉매(phase transfer catalyst ; PTC)로 유도하기 위해 고분자 물질로 지지된 크라운 에테르(polymer-supported crown ether ; Ps-CE)류를 합성하고, 이들 Ps-CE(solid phase)를 이용하여 액-고-액 3상 불균일계에서의 1-bromooctane(유기층)의 iodide(수용층) 친핵 치환 반응속도를 측정하고 그 상이동 촉매능을 연구검토하였다. Ps-CE류는 hydroxymethyl기를 지니는 크라운 에테르류를 합성한 후 이를 1∼2% cross-linked chloromethylated polystyrene 에그라프트시켜 제조하였다. 3상 불균일계치환반응은 반응기질의 농도에 의존하는 유사 일차반응이었고 반응속도상수$(k_{obsd})$는 사용한 촉매량에 비례하였으며, 가교밀도, 온도, 용매 등에 영향을 받음을 알 수 있었다. Ps-CE의 촉매능을 구조적으로 유사한 가용성 크라운 에테르의 촉매능과 비교하였으며, 반응 후 단순히 여과분리하고 이를 PTC로서 반복사용하였을때 촉매능의 감소없이 재사용이 가능함을 알 수 있었다. 반응의 활성화 엔탈피 및 엔트로피는 각각 10∼20kcal $mol^{-1}, 20~55eu.이었고 활성화 자유 에너지는 ∼30kcal mol^{-1}$,/TEX>이었다.

• 공업화학
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• 제3권4호
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• pp.595-604
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• 1992

음이온기를 갖는 카보네이트형 폴리우레탄을 NCO-말단 프레폴리머법으로 제조하여 이를 제막하고 에탄올수용액분리 성능을 검토하였다. 우레탄수지의 물성을 향상시키기 위해 카보네이트형 폴리올(PTMCG)을 사용하였고, 친수성 향상에는 사슬연장제로 ${\alpha}^{\prime},{\alpha}^{{\prime}{\prime}}$-dimethylpropionic acid를 이용하였으며, trimethylamine으로 우레탄 사슬내의 카르복실기를 이온화시켰다. 우레탄 사슬내의 음이온기 형성을 확인하기 위해 모델반응을 실시하여 IR 분광분석을 행하였으며, 합성한 우레탄수지의 IR 스펙트럼과 비교하였다. 사슬연장제와 폴리올의 반응몰비율이 3:1에서 5:1인 범위에서는 hard segment의 농도, 수소결합 등이 우레탄수지의 물성을 기여하고 있음을 알 수 있었다. DSC에 의한 열분석결과 카르복실기를 함유한 카보네이트형 폴리우레탄수지(PU)는 $Tg-25^{\circ}C$ 및 Tm $45^{\circ}C$의 값을 갖는 것으로 나타났으며, 이를 이온화하여 사슬내에 음이온성기를 갖게한 카보네이트형 폴리우레탄수지(APU)의 경우 PU 수지보다 $8{\sim}10^{\circ}C$ 정도씩 낮은 온도 영역으로 전이되는 경향을 나타내었다. PU 및 APU 수지를 용매로 N, N-dimethylformamide(DMF), 가교제로 hexamethylene diisocyanate(HMDI)를 사용하여 캐스팅법으로 투과증발막을 제조하였다. 팽윤도 측정결과 혼합물중 에탄올농도에 따라 증가하는 경향을 나타내었고, 가교를 통하여 막의 팽윤도를 조절하였으며, 이를 투과증발에 응용한 결과 선택도 2.3~9.8, 투과유량 $27{\sim}79.5g/m^2hr$를 갖는 것으로 나타났다. 또한 폴리올의 분자량을 2,000에서 1,000으로 줄임으로 분리성능을 향상시킬 수 있었다.