• 한국고분자학회지:고분자과학과기술
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• 제15권6호
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• pp.702-712
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• 2004

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1499-1500
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• 2011

In this paper, we investigated the electrical properties change of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-pentacene) depending on polymer blend. We fabricated organic thin film transistor (OTFT) using blending solution of small molecule and polymer. In this study poly(2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV), poly (9-vinylcarbazole) (PVK), poly [N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (poly-TPD), poly(${\alpha}$-methyl styrene), Poly(methyl methacrylate) (PMMA) are used as a polymer. Fabricated OTFT with blending solution of TIPS-pentacene and PVK shows best performance in this experiment. OTFT fabricated by blending solution of TIPS-pentacene and PVK shows field effect mobility of 0.0189 $cm^2/V{\cdot}s$, on/off ratio of 1.9E-5 and threshold voltage of 7.4 V.

• Macromolecular Research
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• 제16권7호
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• pp.631-636
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• 2008

The intrinsic viscosities were determined for poly(DL-lactic acid) (PDLLA) solutions in 1,2-dialkyl phthalate at temperatures ranging from 30 to $60^{\circ}C$. A series of dialkyl phthalate, in which the alkyl group was changed from methyl to propyl, was used as the solvent to control the solvent quality systematically. The intrinsic viscosity of the PDLLA solution was higher in the better quality solvent, with a higher molecular weight of PDLLA, and at lower temperatures. The unperturbed dimensions of the PDLLA molecule and polymer-solvent interaction parameter of PDLLA in dialkyl phthalate were deduced using extrapolation methods based on the temperature-dependent intrinsic viscosities. Slight shrinkage in the unperturbed chain dimension was observed, which resulted from a change in polymer conformation with temperature. It was also observed that the polymer-solvent interaction became more favorable with the dialkyl phthalate containing a shorter alkyl chain.

• Korea-Australia Rheology Journal
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• 제13권1호
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• pp.19-27
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• 2001

In this symposium paper, the migration and hydrodynamic diffusion of non-colloidal, spherical particles suspended in polymer solutions are considered under Poiseuille or torsional flows. The migration phenomena in polymer solutions are compared with those in Newtonian fluids and the effect of fluid elasticity is discussed. The experimental results on particle migration in dilute polymer solution reveal that even a slight change in the rheological property of the dispersing medium can induce drastic differences in flow behavior and migration of particles, especially in dilute and semi-concentrated suspensions.

• Macromolecular Research
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• 제10권3호
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• pp.174-177
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• 2002

Proton-conducting hybrid materials composed of silica and Nafion polymer were prepared from the sol-gel synthesis of silica in aqueous Nafion solution. The compositions of hybrid proton conductors were adjusted with the changing ratios of tetraethyl orthosilicate to Nafion. The thermal analysis, FTIR, SEM, and X-ray diffraction studies have proved the formation of Nafion/silica hybrid materials and no remarkable phase separation was observed, which led to an assumption that the macromolecular chain of silica and Nafion was homogeneously interlaned.

• BMB Reports
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• 제31권4호
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• pp.384-390
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• 1998

DNA fragments (51-587 bp) were separated by capillary electrophoresis using entangled polymer, hydroxyethylcellulose, in uncoated fused silica capillary columns. The factors affecting the separation of DNA fragments with hydroxyethylcellulose media were evaluated, i.e., the concentration of buffer and entangled polymer, effects of additives (methanol, ethidium bromide, EDTA), temperature, and injection methods. Maximum performance was obtained by adding 5% methanol in 0.5% hydroxyethylcellulose solution at $30^{\circ}C$. Addition of methanol in polymer media increased the resolution of small size DNA fragments (< 100 bp). On the other hand, addition of ethidium bromide and EDTA, which are commonly used in conventional DNA separation, reduced the resolution of DNA fragments in the polymer solution. It turns out that the separation behavior of DNA in entangled polymer is more sensitive to the running condition compared to that in polyacrylamide gel-filled capillary, but the reproducibility of DNA separation in entangled polymer is reliable.

• 공업화학
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• 제9권2호
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• pp.200-206
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• 1998

수면전개법에 의해 제조된 박막의 두께에 대한 고분자용액의 표면장력과 점도의 영향을 검토하였다. 수면에서 고분자용액의 전개는 고분자용액의 표면장력과 점도에 의해 지배되며, 수면전개 박막의 두께도 이들 인자의 영향을 받는다. 고분자의 농도가 증가함에 따라 고분자용액의 표면장력과 점도는 증가하였으며, 표면장력의 크기는 PVC>PS>CA이었고, 점도의 크기는 CA>PS>PVC 였다. 고분자용액의 수면전개시 물과 고분자용액의 표면장력의 차는 전개구동력으로 작용하나 고분자용액의 표면장력과 점도는 전개저항으로 작용하였다. 수면전개 박막의 두께에 대한 고분자용액의 점도영향이 표면장력에 의한 영향 보다도 더 컸으며, 수면 전개 박막의 두께는 PS>CA>PVC 순으로 두꺼웠다.

• Korea-Australia Rheology Journal
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• 제13권3호
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• pp.141-148
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• 2001

In this research, experimental studies leave been performed on the hydrodynamic interaction between a spherical particle and a plane wall by measuring the force between the particle and wall. To approach the system as a resistance problem, a servo-driving system was set-up by assembling a microstepping motor, a ball screw and a linear motion guide for the particle motion. Glycerin and dilute solution of polyacrylamide in glycerin were used as Newtonian and non-Newtonian fluids, respectively. The polymer solution behaves like a Boger fluid when the concentration is 1,000 ppm or less. The experimental results were compared with the asymptotic solution of Stokes equation. The result shows that fluid inertia plays all important role in the particle-wall interaction in Newtonian fluid. This implies that the motion of two particles in suspension is not reversible even in Newtonian fluid. In non-Newtonian fluid, normal stress difference and viscoelasticity play important roles as expected. In the dilute solution weak shear thinning and the migration of polymer molecules in the inhomogeneous flow field also affect the physic of the problem.

• Korea-Australia Rheology Journal
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• 제15권1호
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• pp.27-33
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• 2003

Associating polymers are hydrophilic long-chain molecules to which a small amount of hydrophobic groups (hydrophobes) is incorporated. In aqueous solution, the association interactions result in the formation of three-dimensional network through flowerlike micelles at high concentrations. In colloidal suspensions, the associating polymers act as flocculated by bridging mechanism. The rheological properties of suspensions flocculated by associating polymers end-capped with hydrophobes are studied in relation to the bridging conformation. At low polymer concentrations, the polymer chains effectively form bridges between particles by multichain association. The suspensions are highly flocculated and show typical viscoelastic responses. When the polymer concentration is increased above the absorbance at saturation, the excess polymer chains remaining in the solution phase build up three-dimensional network by associating interactions. Since the presence of particles does not significantly influence the network structures in the medium, the relative viscosity, which gives a measure of the degree of flocculation is decreased with increasing polymer concentration. The bridging conformation and flocculation level vary strongly depending on the polymer concentrations.

• Korea-Australia Rheology Journal
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• 제21권4호
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• pp.245-268
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• 2009

Recent developments in dilute polymer solution rheology are reviewed, and placed within the context of the general goals of predicting the complex flow of complex fluids. In particular, the interplay between the use of polymer kinetic theory and continuum mechanics to advance the microscopic and the macroscopic description, respectively, of dilute polymer solution rheology is delineated. The insight that can be gained into the origins of the high Weissenberg number problem through an analysis of the configurational changes undergone by a single molecule at various locations in the flow domain is discussed in the context of flow around a cylinder confined between flat plates. The significant role played by hydrodynamic interactions as the source of much of the richness of the observed rheological behaviour of dilute polymer solutions is highlighted, and the methods by which this phenomenon can be incorporated into a macroscopic description through the use of closure approximations and multi scale simulations is discussed.