• Analytical Science and Technology
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• v.17 no.2
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• pp.163-172
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• 2004

The molecular size distribution and fluorescence properties of soil fulvic acids (FA) were characterized by using gel filtration chromatography (GFC) and luminescence spectroscopy. The objectives of this work were to fractionate the FA extracted from a forest soil into different nominal molecular size using GFC system and to characterize the fluorescence properties (excitation, emission and synchronous) of these fractions using luminescence spectrometer. The GFC column was calibrated with polyethylene glycols, acetone and dextrane Blue. The total permeation volume of the GFC system was 404 mL and the void volume 130 mL. The GFC molecular weight of the soil FA was in the range of 190~8,900 Dalton and the molecular weight at the peak on the chromatogram was 930 Dalton. The fluorescence intensity ratio ($I_{498nm}/I_{390nm}$) was found to be increased with an increasing molecular weight. This results may suggest that the fulvic acid fractions with high molecular weight have large amount of the condensed aromatic compound.

• The Korean Journal of Rheology
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• v.2 no.2
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• pp.45-55
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• 1990

분자량이 큰 고분자의 구조가 점탄성에 미치는 영향을 설명하기 위해 선형-선형 고 분자 블랜드에 적용되었던 equivalent primitive chain 모델을 블랜드의 긴 완화시간을 갖는 사슬이 엉킴이중용한 star 고분자를 포함하는 고농도 용액에 까지 확장한다. 긴 완화시간을 갖는 사슬의 완화현상에서 이 사슬의 국부에서 주의 사슬들의 제약이 해제되므로서 일어나 는 현상의 고려하여 분자량과 사슬구조는 다르나 화학적 성질은 같은 이성분계 고분자 블랜 드의 유변학적 거동을 설명한다.

• The Korean Journal of Rheology
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• v.9 no.1
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• pp.27-32
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• 1997

GM 은 Amorphopallus Konjac K. Koch의 tuber의 주성분으로알카리 응고제를 첨가 함에 따라 열적으로 안정한 gel을 형성한다. GM에 침전제로 메탄올을 사용하여 4단계로 분 별하였고 각 분별물(F.1, F.2, F.3, F.4)들은 Mark-Houwink 식을 이용하여 분자량을 산출하 였다. Ubbelohde를 이용한 농도에 따른 환산점도로부터 고유 점성도값을 구한 결과 분자량 이 높은 분별물이 분자량이 낮은 분별물에 비하여 직선으로부터 벗어남을 알수 있었다. 또 한 고유점성도는 분자량이 증가할수록 증가하였고, 분자량 분포 범위가 broad하게 나타났다. GM용액의 frequency와 shear rate에 따른 viscosity를 측정한결과 낮은 frequency에서는 loss modulus(G＂)가 storage modulus(G＂)보다 큰 값을 가졌으나 높은 frequency에서는 G ＇가 G＂보다 크게 나타났다. 이 현상은 분자들의 얽힘에 관한 시간 의존도로써 설명할수 있다. 즉높은 frequency에서는 탄소 사슬간의 얽힘들이 진동기간내에 분자결합이 끊어지기 에 충분한 시간을 갖지 못하여 그 조직이 교차 결합을 한 gel처럼 행동하게 되고 한편 낮은 frequency에서는 탄소사슬들의 얽힘이 풀리고 흐르기에 충분한 시간을 갖게된다. Shear rate에 따른 viscosity값과 frequency에 대한 dynamic viscosity값은 거의 유사한 변화를 나 타내었다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.989-994
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• 2005

The treatment efficiency and the degradation characteristics of humic acid were investigated in three processes-GAC adsorption, Ozone alone and Ozone/GAC hybrid process, in which $UV_{254}$, DOC, molecular size distribution and surface change of GAC were evaluated. DOC removal rate in Ozone/GAC hybrid profess(ca. 80%) was higher than the arithmetic sum of Ozone alone(38%) and GAC adsorption(19%). This result approves that the combined Ozone/GAC hybrid process brings synergistic effects on DOC removal from the HA containing water. $UV_{254}$ decrease rate was also at the highest in Ozone/GAC hybrid process from the three processes. It may be interpreted that the granular activated carbon in Ozone/GAC hybrid process acts as not only an adsorbent but also a catalyst for ozonation, and futhermore offers an additional reaction site between adsorbed organic matter and ozone. In the study of molecular sire distribution, there was no significant change of molecular size distribution in the GAC adsorption process during the reaction time of 120 min. In Ozone alone process, the fraction of molecular size over 30 kDa was decreased a little at the beginning and left constant after 10 min. But in Ozone/GAC hybrid process, the molecules size over 30 kDa of HA was significantly decreased from 36.3% to 3.9%. And also the fraction of smaller molecular size below 0.5 kDa was increased from 4.8%(untreated HA) to 12.3%(in Ozone alone) and 40.1%(in Ozone/GAC) respectively at the reaction time of 120 min.

• Membrane Journal
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• v.12 no.1
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• pp.21-27
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• 2002

The formation of soluble microbial products(SMP) and molecular weight distribution on loading rate were observed in batch-type culture medium, which phenol was fed as a substrate. The molecular weight destribution was obtained by using 30K, 100K dalton and $0.45{\mu}$ membrane filters. When the phenol concentrationas a substrate was 120, 230 and 440 mg/L , the specific substrate utilization rate(q) showed 0.639, 1.281 and 1.744 mgTOC/mgMLSS/day, respectively. The endogenous biomass decay rate constant($K_d$) at each substrate concentration was 0.00536, 0.0661 and 0.0749($day^1$), respectively. The $SMP_e$ product rate constant($k_{SMP}_ e$) showed 0.006, 0.0058 and 0.0057($day^1$), respectively. The initial influent substrate during the course of time degraded and produced $SMP_s$. The $SMP_s$ was converted to the $SMP_{nd}$ and endogenous phase converted to the $SMP_e$ ingredients. The molecula weight distribution on loading rate was converted to a higher MW during the course of time.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.300-302
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• 2001

폴리카본산계 기능성 고분자를 합성해서 고성능 감수제 원료로 활용하여 고유동화 혼화제를 개발하고자 한다. 폴리카본산계 기능성 고분자를 합성한 후, 이를 고유동, 고강도 혼화제 원료로의 제반 물성을 확인하고, 이를 현장에 적용하여 현재의 제품을 획기적으로 개선하고, 혼화제 품질의 우위성을 확보하기 위해 1) 시멘트 및 골재 표면에서의 적절한 계면활성을 갖는 분자설계를 하였으며, 2)분자량의 조절 기술의 개발을 개발하였다. 합성에 있어서 첫째, 시멘트 및 골재 표면에서의 적절한 계면활성을 갖는 분자설계와 둘째, Mw 5,000정도의 분자량을 갖는 감수제의 합성기술을 개발하였다. 이렇게 제조된 고성능 유동화제의 화학구조 해석을 해석하고 분자량 및 분자량 분포를 측정한 다음, 시멘트 페이스트의 유동성, 점도, 슬럼프로스 등을 측정하여 고성능 유동화제의 성능인 시멘트 페이스트의 유동성을 시험하였다. 그 결과 고유동성을 갖는 것과 장시간 안정한 유동성을 나타내었으며, 경과 시간에 따른 겉보기 점도변화를 측정한 결과 점도의 상승이 초기에 일어나다가 시간의 경과에 따라 점도가 감소하는 경향을 나타내었다. 따라서 경과시간에 따른 유동성 손실을 억제할 것으로 기대한다.

• Elastomers and Composites
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• v.44 no.4
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• pp.397-400
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• 2009

Ozone caused the crack on the surface of a rubber article by oxidation of double bond at room temperature. Wax migrates to the surface of a rubber article and makes a physical barrier to prevent process of ozonation. We investigated change of molecular weight distribution of waxes in unfilled NR, SBR, and BR vulcanizates before and after aging at room temperature for 6 months. Migration and evaporation behaviors of wax in a rubber article at ambient conditions help understand a role of wax as an antidegradant and appearance contamination of a rubber article. The relative intensity distribution of n-alkanes of the NR specimen after the aging was shifted to higher molecular weight compared with the relative intensity distribution before the aging, while those of the SBR specimen before and after the aging did not show a big difference.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.159-164
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• 1998

Polycarbosilane(PCS) as a SiC precursor was synthesized from the rearrangement reaction of polydimethysilane(PDMS) in an autoclave, which prepared by dehalocoupling reaction of dichlorodimethylsilane. After fractional precipitation into three fractions in n-hexane-methanol mixture, they were characterized by FT-IR, NMR, GPC, TGA/DSC and XRD, and compared with the commercial product. We found that the molecular weight distributions of the PCS depended on the reaction pressures, temperatures and the reaction times, and affected thermal property and ceramic yield of the polymer. The monodispersed PCS containing less amount of oligomers and nonsoluble products was prepared by reaction of PDMS at $420^{\circ}C$ for 10 hrs, and it also gave the greatest amount of medium molecular weight($M_n=4,000$) fraction.

• Polymer(Korea)
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• v.39 no.3
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• pp.388-393
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• 2015

Low molecular weight species were extracted from PC and SAN by a solvent extraction method in order to investigate the effect of low molecular weight species on interfacial tension and affinity between PC and SAN. From the analysis of molecular weight distribution by the GPC, it was confirmed that the low molecular weight species were effectively eliminated by the solvent extraction. Interfacial tension measurements and morphological observation were carried out with the PC and SAN of which the low molecular weight species were extracted. Interfacial tension was increased and the infinity was decreased for the extracted PC and SAN pair. This result implied that the low molecular weight species play a role as a compatibilizer between two polymers. Among two polymers, low molecular weight SAN contributes more in the compatibilization. Thus, it is favorable to use SAN containing a larger amount of low molecular weight species in fabrication of PC/ABS blend.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.04b
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• pp.59-61
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• 1997

최근 신소재에 관한 연구는 첨단기술 발전에 주요한 역할을 하고 있음은 주지의 사실이며, 특히 다목적, 다기능 고분자는 여러 분야에 활용되므로 이에 관한 집중적인 연구가 활발히 진행되고 있다. 고분자는 보통 화합물과는 달리 여러 분자량의 중합체가 분포되어 있으므로 물리-화학적 특성을 알아내기가 힘들뿐만 아니라, 이러한 고분자 물질의 분자량, 분자량 분포 등의 정보가 폭 넓게 파악되어야만 그 물질의 정확한 활용과 소재 개발이 가능하다. 특히 protein 등과 같은 생체 고분자들은 유전, 특정 반응에 작용하는 효소, 호르몬 등 수많은 연구가 진행 중에 있으나 그 분리.정제 과정은 상당히 어려우며, 경우에 따라서는 분리. 정제 과정에서 활성을 잃은 경우도 있다. 따라서 이러한 고분자들의 물성을 확인하는 과정이 최우선적으로 필요하다.