• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4028-4034
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• 2012

Tris(2-phenylphenoxo)aluminum ($(2-PhC_6H_4O)_3Al$) exists as a dimeric form in toluene. When toluene-insoluble anhydrous cobalt acetate is treated with tris(2-phenylphenoxo)aluminum in toluene, the toluene-soluble adduct $(2-PhC_6H_4O)_3Al{\cdot}Co(OAc)_2$ is formed. The 2-phenylphenoxo ligand in the adduct can be replaced with another aryloxo ligand to give (aryloxo)$(2-PhC_6H_4O)_2Al{\cdot}Co(OAc)_2$ (aryloxo = 2-methylphenoxo, 2-isopropylphenoxo, 4-methylphenoxo, 4-isopropylphenoxo, or 4-tert-butylphenoxo). These complexes are active for butadiene polymerization without gel formation when activated with an equivalent amount of $(2-PhC_6H_4O)AlEt_2$ for 2 h. The highest activity, 175 kg/mol-Co (turnover number, 3200) was achieved with $(2-PhC_6H_4O)_3Al{\cdot}Co(OAc)_2$ at $65^{\circ}C$ for 2 h. The microstructure of the polymer chains is mostly trans-1,4-configuration (70-75%) with the remaining being 1,2-vinyl. The cis-1,4-configuration observed by IR is minimal (1-5%). By replacing the 2-phenylpheoxo with a 4-alkylphenoxo ligand, the amount of 1,4-configuration slightly increases, resulting in increase in the endothermic melting signal at $-30{\sim}50^{\circ}C$ in the DSC curve. The molecular weights of the polymers are high ($M_n$: 300000~800000) with a fairly narrow molecular weight distribution ($M_w/M_n$, 2.0-2.7).

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.540-544
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• 2008

Pyrolytic characteristics of mixed plastics containing 22 wt.% HDPE, 17 wt.% LDPE, 27 wt.% PP, 12 wt.% PS, 16 wt.% ABS, 6 wt.% PVC have been studied in the batch-type microreactor of stainless steel. Thermal degradation experiments were performed at temperature of $410{\sim}450^{\circ}C$. The yield of each pyrolytic products were obtained by the weight measurement and molecular weight distribution of pyrolytic liquid products determined by the GC-SIMDIS method. It was shown that the yield and molecular weight of pyrolytic liquid product were decreased with the increase of reaction temperature and time. It was know that 20wt% of PVC composing of the mixed plastics was converted to the gas products of chloride during the pyrolysis process. The chain-end scission rate parameter was determined to be 50.2 kcal/mole of mixed plastics by the Arrhenius plot.

• Elastomers and Composites
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• v.48 no.4
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• pp.263-268
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• 2013

In this study, we prepared poly(ethylene-ter-1-hexene-ter-divinylbenzene) using bridged rac-$Et[Ind]_2ZrCl_2$ metallocene catalysts. The effect of 1-hexene on the terpolymerization rate was evaluated. When cocatalyst/catalyst molar ratio was 3,000, catalytic activity indicated more than 8,000 which was very remarkable value. As polymerization time increased, the weight-average molecular weight of the terpolymer gradually increased to some degree. In case of a polymerization time of 50 minutes, the terpolymer became amorphous state. The molecular weight distribution and densities of the terpolymer were 110,000-200,000 and $0.85-0.89g/cm^3$, respectively. Thermal properties and structure of the terpolymer were also identified.

• Korean Journal of Food Science and Technology
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• v.34 no.5
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• pp.757-761
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• 2002

Proximate composition, phenolic compounds, and amino acid composition of molokhia (Corchorus olitorius) and molecular weight distribution of its mucilage were determined. Concentrations of dietary fibers and protein were 37.4 and 24.4% of the total dry weight, respectively. Mucilage was obtained by extracting dry molokhia leaves with hot water, followed by the addition of 55% ethanol. Although about 50% of the mucilage was lost during the extration, it was still rich in polyphenol compounds. In mucilage, proteins were composed of glutamic acid, glycine, alanin, and aspartic acid, and molecular weight of most polysaccarides ranged from $40,000{\sim}500,000$ daltons based on gel filtration chromatography.

• Polymer(Korea)
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• v.37 no.1
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• pp.74-79
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• 2013

Polyvinylidene fluoride (PVDF) and its copolymer with hexafluoropropylene (HFP) were successfully prepared from free radical solution polymerizations using diisopropyl peroxidicarbonate (DIPPDC) in the presence of 1,1,2-trichlorotrifluoroethane (R-113). The reactivity ratios of VDF and HFP were estimated as$r_{VDF}=2.06{\pm}0.03$ and $r_{HFP}{\approx}0$. This result indicates that HFP cannot undergo self propagation. The weight-average molecular weight and molecular weight distribution of copolymers were found to decrease with increasing HFP content. The melting temperature of copolymers linearly decreased with the increase of HFP content because of the introduction of HFP. Moreover, no melting peak was observed for the copolymers with high HFP content. The glass transition temperature of copolymers gradually increased with the increase of HFP content due to the restricted flexibility of the polymer chains.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.279-284
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• 2013

The phenolic beads in macrosize range were obtained by suspension polymerization at $98^{\circ}C$ from phenol and formaldehyde in the presence of basic catalyst with a phenol to formaldehyde (P/F) range of 1:1~1:4, and they were carbonized to spherical carbon beads under nitrogen at $700^{\circ}C$. Thermal analysis on spherical phenolic beads obtained by suspension polymerization showed that the postcuring process is essential. In order to optimize the suspension polymerization, the effects of the P/F molar ratio, the pH of catalyst, and the molecular weight of stabilizer on the size distribution and yield of spherical phenol beads were examined separatively. The particle size was increased whereas the yield was decreased with P/F molar ratio. The increasing basicity of catalyst made the particle size to increase, while the molecular weight of stabilizer had more effect on the yield rather than on the particle size distribution. The thermal stability of the spherical phenolic beads obtained through postcure was also examined by TGA. The phenol beads of high P/F ratio still showed the weight loss at $220^{\circ}C$ even after postcure due to the high possibility of dibenzyl ether, while those of low P/F ratio showed the steady decrease in weight during $220^{\circ}C$ to $400^{\circ}C$, which showed that the optimal P/F ratio was 1:2.

• Korea-Australia Rheology Journal
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• v.17 no.3
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• pp.125-130
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• 2005

Coalescence process of binary immiscible fluid mixtures having bimodal size distributions, prepared by mixing two pre-sheared samples at different shear rates, ${\gamma}_{pre1}\;and\;{\gamma}_{pre2}$, under shear flow at a final shear rate, ${\gamma}_f$, are examined by transient shear stress measurements and microscopic observations in comparison with the results for simply pre-sheared samples having narrow size distributions (unimodal distribution samples). Component fluids are a silicone oil (PDMS) and a hydrocarbon-formaldehyde resin (Genelite) and their viscosities are 14.1 and 21.0 $pa{\cdot}sec$ at room temperature $(ca.\;20^{\circ}C)$, respectively. The weight ratio of PDMS: Genelite was 7:3. Three cases, $({\gamma}_{pre1}=7.2sec^{-1},\;{\gamma}_{pre2}=12.0sec^{-1}\;and\;{\gamma}_f=2.4sec^{-1}),\;({\gamma}_{pre1}=0.8sec^{-1},\;{\gamma}_{pre2}=4.0sec^{-1}\;and\;{\gamma}_f=2.4sec^{-1}),\;and\;({\gamma}_{pre1}=7.2sec^{-1},\;{\gamma}_{pre2}=12.0^sec^{-1}\;and\;{\gamma}_f=7.2sec^{-1})$ the first case, transient shear stress did not show any significant difference but domains larger than the initial state are observed at short times. In the latter cases, there exist undershoot of shear stress, reflecting existence of deformed large domains, which is confirmed by the direct observation. It is concluded that coalescence between large and small domains more frequently occur than coalescence between the domains with similar size in the bimodal distribution samples.

• Food Science and Biotechnology
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• v.16 no.4
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• pp.600-604
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• 2007

In this study, we first prepared 3 kinds of powders with different molecular masses from the crude protein-bound polysaccharide extract of Agraricus blazei Murill through ultrafiltration, followed by spray-drying. Then, the antitumor activities of the powders were analyzed. Size exclusion chromatography coupled with a multi-angle laser-light-scattering system showed the 3 powders had the following molecular ranges: below 10 kDa (SD-1), 10 to 150 kDa (SD-2), and above 150 kDa (SD-3), representing peak molecular weights of $8.26{\times}10^3,\;9.65{\times}10^4$, and $5.94{\times}10^6\;g/mol$, respectively. All the powders stimulated macrophage RAW264.7 cells to produce nitric oxide, of which SD-2 and SD-3 were superior to the crude extract powder (CP-SD), while SD-1 showed the lowest activity. Similar results were found for their cytotoxicities against human cancer cell lines (A549, MCF-7, and AGS), where the highest activity was obtained with the SD-2 treatment for 72 hr at $1,000\;{\mu}g/mL$. The MCF-7 cell line was less sensitive to the powders than the other cells. From this research we found that ultrafiltration, in combination with spray-drying, is applicable for preparing protein-bound polysaccharide powders with higher antitumor activities.

• Advances in materials Research
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• v.6 no.3
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• pp.303-316
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• 2017

In this article, novel olefin polymerization catalyst with lower cost and simple synthetic process were developed, $ArOTiCl_3$ complexes [$(2-OMeC_6H_4O)TiCl_3(C1)$, $(2,4-Me_2C_6H_3O)TiCl_3(C2)$, $TiCl_3(1,4-OC_6H_4O)TiCl_3(C3)$, $TiCl_3(1,4-OC_6H_2O-Me_2-2,5)$ $TiCl_3(C4)$] and corresponding $(ArO)_2TiCl_2$ complexes [$TiCl_2(OC_6H_4-OMe-2)_2(C5)$ and $TiCl_2(OC_6H_3-Me_2-2,6)_2(C6)$] have been synthesized by the reaction of $TiCl_4$ with phenol, all these complexes were well characterized with $^1H$ NMR, $^{13}C$ NMR, MASS and EA. When combined with methylaluminoxane (MAO), the $ArOTiCl_3/MAO$ system shows high activity for ethylene copolymerization with 1-octene and copolymer was obtained with broaden molecular weight distribution (MWD). The $^{13}C$ NMR result of polymer indicates that the 1-octene incorporation in polymer reached up to 8.29 mol%. The effects of polymerization temperature, concentration of polymerization monomer and polymerization time on the catalytic activity have been investigated.

• Journal of Pharmaceutical Investigation
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• v.29 no.3
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• pp.193-203
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• 1999

In order to investigate systematically the steady shear flow properties of aqueous po1y(ethylene oxide) (PEO) solutions having various molecular weights and concentrations, the steady flow viscosity has been measured with a Rheometrics Fluids Spectrometer (RFS II) over a wide range of shear rates. The effects of shear rate, concentration, and molecular weight on the steady shear flow properties were reported in detail from the experimentally measured data, and then the results were interpreted using the concept of a material characteristic time. In addition, some flow models describing the non-Newtonian behavior (shear-thinning characteristics) of polymeric liquids were employed to make a quantitative evaluation of the steady flow behavior, and the applicability of these models was examined by calculating the various material parameters. Main results obtained from this study can be summarized as follows: (1) At low shear rates, aqueous PEO solutions show a Newtonian viscous behavior which is independent of shear rate. At shear rate region higher than a critical shear rate, however, they exhibit a shear-thinning behavior, demonstrating a decrease in steady flow viscosity with increasing shear rate. (2) As an increase in concentration and/or molecular weight, the zero-shear viscosity is increased while the Newtonian viscous region becomes narrower. Moreover, the critical shear rate at which the transition from the Newtonian to shear-thinning behavior occurs is decreased, and the shear-thinning nature becomes more remarkable. (3) Aqueous PEO solutions show a Newtonian viscous behavior at shear rate range lower than the inverse value of a characteristic time $1/{\lambda}_E$, while they exhibit a shear-thinning behavior at shear rate range higher than $1/{\lambda}_E$. For aqueous PEO solutions having a broad molecular weight distribution, the inverse value of a characteristic time is not quantitatively equivalent to the critical shear rate, but the power-law relationship holds between the two quantities. (4) The Cross, Carreau, and Carreau-Yasuda models are all applicable to describe the steady flow behavior of aqueous PEO solutions. Among these models, the Carreau-Yasuda model has the best validity.