• Polymer(Korea)
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• v.32 no.4
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• pp.385-389
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• 2008

Chain propagation and chain transfer in anionic polymerization of hexafluoropropylene oxide were investigated under various reaction conditions such as the stabilization of reaction temperature, the amount of hexafluoropropylene solvent, and the feeding rate of hexafluoropropylene oxide monomer. Anionic initiator for the polymerization was synthesized from cesium fluoride and hexafluoropropylene oxide in tetraethyleneglycol dimethylether. It was possible to obtain a high molecular weight poly(HFPO) ($M_w$ 14800) using the anionic initiator in conditions of stabilized reaction temperature, and optimized addition of solvent and monomer feeding (HFP/initiator mole ratio=31.5 and HFPO feeding rate=11.67 g/hr). Otherwise, chain transfer reaction in anionic polymerization was increased. From the results of molecular weight in various reaction conditions, it was found that chain propagation and chain transfer in anionic polymerization of HFPO were very sensitive to reaction conditions.

• Polymer(Korea)
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• v.34 no.6
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• pp.574-578
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• 2010

In this study, the caprolactone modified hydroxy acrylates (CHAs) were synthesized by ring-opening reaction of caprolactone and 2-hydroxyethyl acrylate (2-HEA) as initiator. Also, the caprolactone modified urethane acrylate (UA) oligomers were synthesized by condensation reaction of previously synthesized CHAs, 2-hydroxyethyl acrylate (2-HEA) and hexamethylene diisocyanate trimer (HDT). Using the hydroxy number of CHAs, the molecular weights of the CHAs were calculated easily and their molecular weight was similar to the theoretical molecular weight of them. The viscosity of UA oligomers decreased as increasing a content of CHA in the UA oligomer. Cure films were prepared from UA oligomer, reactive diluents, and UV initiator to investigate their physical properties. The thermal stability and color difference on high temperature for the cured film were improved as increasing the crosslinking density. Their surface hardness was also increased as increasing crosslinking density of the cured films, but their elongation at break was decreased.

• Journal of the Korean Applied Science and Technology
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• v.30 no.4
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• pp.754-760
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• 2013

We investigated an electrochemical properties for Langmuir-Blodgett (LB) monolayer films of sphingomyelin(SP) and polyamic acid(PAA) mixture(1:1, 2:1 and 3:1 molar ratio). LB monolayer films of mixture was deposited by the LB method on the indium tin oxide(ITO) glass. The electrochemical properties measured by cyclic voltammetry with three-electrode system in 0.1N $KClO_4$ solution. As a result, LB monolayer films of SP and PAA mixture was appeared on irreversible process caused by the reduction current from the cyclic voltammogram. Diffusion coefficient(D) in the SP and PAA mixture was calculated $2.670{\times}10^{-5}$, $3.562{\times}10^{-5}$ and $1.005{\times}10^{-5}cm^2s^{-1}$ at 1:1, 2:1 and 3:1 molar ratio, respectively.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.302-312
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• 2004

This paper presents the experimental results on the properties of the cement mortar with polycarboxylate-type superplasticizers PCA) which were synthesized by different mole ratio of methoxypoly(ethyleneglycol)monomethacrylate (MPEGMAA) and methacrylic acid (MAA) and by different length of polyethyleneoxide (PEO). As the PEO chain was longer and mole ratio of [MPEGMAA]/[MAA] was lower, the fluidity of cement mortar was better. The setting time of mortar with PCA was retarded, and as PEO chain was shorter and [MPEGMAA]/[MAA] was lower, it was more retared. Espeacially, when the molecular weight of MPEGMAA was 475(repeat unit of ethylene oxide=l0), the degree of retardation was the highest of them. The surface tensions of PCA solutions were lower than that of water due to the effect of PEO chain, and also the pore size distribution of cement mortar was influenced by it. The pores in cement mortar with PCA at 28 days were macropores in the range of 7 to 370$\mu\textrm{m}$, and accordingly, the densities and compressive strengths of mortar were lower than those of OPC mortar.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.402-406
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• 2013

In this study, a pitch for melt-electrospinning was prepared from naphtha cracking bottom (NCB) oil by the modification with heat treatment. The softening point and property of the modified pitch was influenced by modification conditions such as nitrogen flow rate, heat treatment temperature, and reaction time. Among these, the heat treatment temperature had a very strong influence on the distribution of molecular weight and softening point of the pitch. The C/H mole ratio and average molecular weight increased with increasing the heat treatment temperature due the decomposition and cyclization reaction of surface-functional groups. In addition, the values of benzene insoluble and quinoline insoluble also tends to decrease, and the width of molecular weight distribution seems to get more narrow. The carbon fiber with a diameter of $4.8{\mu}m$ was prepared from a modified pitch at the softening point of $155^{\circ}C$ by melt-electrospinning. It is believed that the melt-electro spinning method is much more convenient to get the thinner fiber than the conventional melt spinning method.

• Polymer(Korea)
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• v.24 no.4
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• pp.488-498
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• 2000

Molecular bottle-brush was prepared by hydrogen-bonding between poly(4-vinylpyridine)(P4VP) as main chain and 3-pentadecylphenol (PDP) as amphiphilic side chain. Variation of long period ( $L_{p}$), order-disorder transition temperature ( $T_{ODT}$) and mesomorphic structure of bottle-brush were investigated by changing various mole ratio (x) of pyridine group in P4VP and PDP and molecular weight of P4VP. Upper critical solution temperature (UCST) behaviour was observed. For x 0.8-0.9, maximum critical temperature was found. As molecular weight of P4VP was increased, phase transition occurred at higher temperature. It was found that phase behaviour of the bottle-brush was affected by mobility of P4VP as well as size and regularity of lamellar structure. The $L_{p}$ determined from analysis of crystal structure was in the range of 35 $\AA$ and 40 $\AA$ and was more affected by the molecular weight of P4VP than by mole ratio (x). However, if the molecular weight of P4VP was high, LP value was little affected.ted.d.

• Journal of Adhesion and Interface
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• v.11 no.3
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• pp.100-105
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• 2010

In this study, polyurethane dispersion was prepared by polyester polyol, 4,4-dicyclohexylmethane diisocyanate ($H_{12}MDI$), dimethylolpropionic acid (DMPA), and monomeric diol. The effect of various monomeric diol, polyol/monomeric diol molar ratio and DMPA contents on the properties of polyurethane dispersion were investigated. As the molecular weight of monomeric diol and monomeric diol molar ratio increased, $T_g$ gradually increased. And when DMPA contents increased, also $T_g$ gradually increased. In the results of mechanical properties, when the molecular weight of monomeric diol, monomeric diol molar ratio of polyol/monomeric diol and DMPA contents increased, tensile strength was increased. Finally, optimum peel strength obtained when polyol/monomeric diol ratio was 8 : 2.

• Microbiology and Biotechnology Letters
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• v.17 no.4
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• pp.397-402
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• 1989

A new extracellular biopolymer was produced by Methylobacterium organophilum from methanol as a sole carbon and energy source. The purified biopolymer was found to have a high molecular weight of about 4-5$\times$10$^6$ dalton and contained 66% (w/w) of carbohydrate but no polyhydro xybutyrate. Other organic constituents were consisted of protein, pyruvic acid, uronic acid, and acetic acid, whereas content of inorganic ash was 22%. Based on the chemical analysis of the biopolymer by TLC method, the polymer was consisted of glucose, galactose, and mannose with an approximate molar ratio of 2:3:2. The biopolymer solution showed a characteristics of pseudoplastic non-Newtonian fluid. The viscosity of the 1%-biopolymer solution was found to be 18,000 cp at a shear rate, 1 sec$^{-1}$, which was almost 10 times higher than that of a commercial xanthan gum.

• Microbiology and Biotechnology Letters
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• v.17 no.5
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• pp.421-428
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• 1989

A soil bacterium synthesizing an extremely viscous biopolymer was isolated and identified as Pseudomonas delafieldii. The optimal pH and temperature for the growth were 6.5 and 3$0^{\circ}C$, respectively. Maximum specific growth rate was 0.24 h$^{-1}$. The specific polysaccharide productivity, growth yield and product yield were 6.25 mg/g-cell/h, 54.5% and 38.39%, respectively. The polysaccharide was presumed to be $\beta$-glucan containing glucose and gluconolactone (1.9：1.0 in molar ratio) and 1.35 % acetyl group, Element analysis showed that it contained carbon (31.85%) and hydrogen (5.15%). The weight average molecular weight by GPC was 5.64$\times$10$^7$. The intrinsic viscosity was 42.84 dl/g.

• Polymer(Korea)
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• v.25 no.1
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• pp.41-48
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• 2001

Polyurethane(PU) microgels were synthesized from poly(caprolactone) diol(PCD) and/or poly(ethylene glycol)(PEG), diisocyanate and 1,2,6-hexane triol by solution polymerization method. A critical gelation concentration of the PU microgels with, mole ratios of PCD/PEG were the important factors influencing the formation and property microgel or macrogels. The physical and thermal properties of the PU microgels prepared with depending upon the structure of diisocyanate, mole ratio of PCD/PEG, and molecular weight of PEG were investigated. It was found that PU microgels were distributed by polydisperse, spherical small particles below 300nm and showed the properties of low viscosity.