• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.130-134
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• 2017

Organic aerosols dispersed in the atmosphere likely undergo phase separation. Such internally mixed particles are often described as comprising an organic phase and an aqueous phase separately. We studied the morphology of two liquid separated aerosols in the sub-microscale by using a simple thermodynamic model with Russian doll geometry. The morphology of particles can be easily predicted from the simple criteria on the surface tension and two algebraic equations (the volume constraint and Young equation). This result may give the potential explanation about the complex morphology of the organic airborne particles.

• Macromolecular Research
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• v.13 no.6
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• pp.529-532
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• 2005

A novel amphiphilic, symmetric rod-coil, triblock copolymer (denoted as PHEMA-b-PF-b-PHEMA) of poly(9,9-didodecylfluorene-2,7-diyl) (PF) and poly(hydroxyl ethyl methacrylate) (PHEMA) was synthesized. A $\pi$-conjugated poly(9,9-didodecylfluorene-2,7-diyl) (PF) was used as a rodlike midblock segment and connected with hydrophilic end blocks of poly(hydroxyl ethyl methacrylate) (PHEMA) by using an ATRP technique. The chemical structure of PHEMA-b-PF-b-PHEMA was confirmed by $^{1}H$-NMR and GPC, and its PL properties were investigated in selected solvents. Due to the dissimilarities in molecular conformation and solubility between PHEMA and PF blocks, both block segments were segregated to display a phase-separated morphology on a Si wafer.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.471-476
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• 2008

The thermal and mechanical properties and morphology of epoxy/polyamide/DDS/2E4MZ-CNS reactive blends with various amounts of polyamide were investigated. The amount of polyamide was 10, 20, and 30 phr and 2 phr of catalyst was added to the blend to cure at $180^{\circ}C$ for 30 min. By adding the catalyst, 2E4MZ-CNS, to the blend, the cure reaction occurred at a lower temperature. From the SEM images, it was found that the boundary of separated-phase was unclear and the phase was co-continuous. Without the catalyst, however, the boundary of separated-phase was clear. The control of cure temperature and morphology could be achieved by using a proper catalyst and consequently the mechanical strength increased by 20% compared to the blend without the catalyst due to the strong interaction between epoxy matrix and phase-separated polyamide at the interface.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.944-948
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• 1999

The morphological properties of four binary blends of polyethylene synthesized by metallocene catalyst(MCPE) and four polyolefins prepared by Ziegler-Natta catalyst have been investigated to interpret the effect of micro-molecular structure on the phase morphology and interfacial behavior; four binary blend systems studied are high density polyethylene(HDPE)-metallocene polyethylene (MCPE), polypropylene(PP)-MCPE, poly(propylene-co-ethylene) (CoPP)-MCPE, and poly(propylene-co-ethylene-co-1-butylene) (TerPP)-MCPE, and they are all phase separated. The HDPE-MCPE blend shows evenly growing homogeneous HDPE domain on the continuous MCPE phase, on the other hand, the rest of three blends show complex heterogeneous phase behavior. The PP-MCPE blend shows that PP and MCPE and completely phase separated and phase inversion takes place at 50% MCPE. The CoPP-MCPE and TerPP-MCPE show enhanced interface due to the same micro-molecular structure of ethylene, and phase inversion takes place at 40% MCPE. In particular, TerPP-MCPE blend shows improved phase morphology between interfaces, and this may be arisen from the comonomer contents in TerPP, which are 1-butene and ethylene having the same chemical structure as that of MCPE. The enhancement of the phase morphology in the TerPP-MCPE blend is correlated with the mechanical and morphological properties. Thus, although the four blend systems are phase separated, the phase morphology suggests that the order of interfacial adhesion strength be HDPE-MCPE > TerPP-MCPE > CoPP-MCPE > PP-MCPE and that micro-molecular structure between constituents be one of major factors giving enhanced interfacial adhesion.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.66-69
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• 1998

Most segmented polyurethanes are prepared from a two-step method where the polyol is end-capped with an excess of diisocyanate, followed by chain extension with stoichiometric amount of chain extender, In the final polymer the hard and soft segments tend to segregate, due to thermodynamic immiscibility and the differences in chemical structure between hard and soft segments, and produce a phase separated morphology of hard segment-rich and soft segment-rich phase. (omitted)

• Polymer(Korea)
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• v.27 no.5
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• pp.413-420
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• 2003

Fluorescence microscope technique was employed for the characterization of phase separation behavior of a 4-chloro-7-nitrobenzofurazan labeled polystyrene (PS) / polybutadiene (PB) blend in dioctyl phthalate under steady shear. It was confirmed that the fluorescence microscope images reflect the real phase morphology by comparing with the images of phase contrast microscope. Comparing the fluorescence intensities from the phase separated domain (PS rich) and continuous phase (PB rich), the composition difference between these two phases were deduced. The observed shear dependence of compositional change is then used to confirm that the phase diagram is indeed shifted under the steady shear.

• Macromolecular Research
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• v.13 no.6
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• pp.514-520
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• 2005

Composite membranes of Nafion and sulfonated poly(arylene ether sulfone) were prepared. Sulfonated poly(arylene ether sulfone)s with different degrees of sulfonation were blended with Nafion to reduce the methanol crossover. The morphology, proton conductivity and methanol permeability of the resulting composite membranes were investigated by SEM, EDAX, AC impedance spectroscopy and permeability measuring instrument. The cross­sections of the composite membranes showed a phase separated morphology. The morphology and phase separation mechanism could be controlled by varying the blend ratio and the degree of sulfonation of poly(arylene ether sulfone). These complex morphologies can be applied for reducing methanol crossover. The methanol permeability and proton conductivity of the composite membranes were lower than those of Nafion 117 membrane since the development of an ionic pathway in the blend membrane was more difficult than that in Nafion itself.

• Korean Journal of Materials Research
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• v.19 no.10
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• pp.562-568
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• 2009

Electrospinning is a technique that produces sub-micron sized continuous fibers by electric force from polymer solutions or melts. Due to its versatile manufacturability and the cost effectiveness, this method has been recently adopted for the fabrication of one-dimensional materials. Here, we fabricated polyacrylonitrile (PAN) polymer fibers, from which uniform carbon fibers with diameters of 100-200 nm were obtained after carbonization at 800 $^{\circ}C$ in N$_2$. Special emphasis was directed to the influence of the phase separated polymer solution on the morphology and the microstructure of the resulting carbon fiber. The addition of poly(stylene-co-acrylonitile) (SAN) makes the polymer solution phase separated, which allows for the formation of internal pores by its selective elimination after electrospinning. XPS and Raman Spectroscopy were used to confirm the surface composition and the degree of carbonization. At the PAN:SAN = 50:50 in vol%, the uniform carbon fibers with diameters of 300$\sim$500 nm and surface area of 131.6 m$^2$g$^{-1}$ were obtained.

• Macromolecular Research
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• v.9 no.1
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• pp.51-65
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• 2001

Two-stage emulsion polymerizations of hydrophobic monomers on hydrophilic seed polymer particles were carried out to make core-shell composite particles. It was found that the loci of polymerization in the second stage were the surface layer of the hydrophilic seed latex particles, and that it has resulted in the formation of either eccentric core-shell particles with the core exposed to the aqueous phase or aggregated nonspherical composite particles with the shell attached on the seed surface as many small separated particles. The driving force of these phenomena is related to the gain in free energy of the system in going from the hydrophobic polymer-water interface to hydrophilic polymer-water interface. Thermodynamic analysis of the present polymerization system, which was based on spreading coefficients, supported the likely occurrence of such nonspherical particles due to the combined effects of interfacial free energies and phase separation between the two polymer phases. A hypothetical pathway was proposed to prepare hydrophilic core-hydrophobic shell composite latex particles, which is based on the concept of opposing driving and resistance forces for the phase migration. It was found that the viscosity of the monomer-swollen polymer phase played important role in the formation of particle morphology.

• Proceedings of the Membrane Society of Korea Conference
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• 1993.04a
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• pp.52-53
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• 1993

The pervaporation behavior of EtOH/Water mixture through IPN membranes was predicted in this study. The pervaporation characteristics of single polymer membrane were modeled according to the "six-coefficients model" proposed by Brun. In the case of the IPN membrane, two models were proposed according to the phase structure of the IPN. For a uniphase membrane with no phase separation, the compositional average of the single polymer membrane was used. in the case of the phase separated IPN's two cases existed. The first was the island and sea model: in which one phase was continuous and the other was dispersed. The second was the co-continuous model where two continuous phases existed. For these cases, the permeation rate and the separation factor of the IPN membrane were calculated using the experimental sorption data and the cornponent polymer properties. Comparison with the experimental data indicated that these models could be used to predict the performances of IPN membranes depending on the morphology of the IPN.