• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1807-1818
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• 2005

New PPV based conjugated polymers, containing terphenyl units, were prepared as the electroluminescent (EL) layer in light-emitting diodes (LEDs). The prepared polymers, poly[2,5-bis(4-(2-etylhexyloxy)phenyl)-1,4-phenylenevinylene] (BEHP-PPV), poly[2-(2-ethylhexyloxy)-5-(4-(4-(2-etylhexyloxy)phenyl)phenyl)-1,4-phenylenevinylene] (EEPP-PPV) and poly[2-(2-ethylhexyloxy)-5-(9,9-bis(2-etylhexyl)fluorenyl)-1,4 phenylenevinylene] (EHF-PPV), were soluble in common organic solvents and used as the EL layer in double layer light-emitting diodes (LEDs) (ITO/PEDOT/polymer/Al). The polymers were prepared by the Gilch reaction. The number-average molecular weight $(M_n)$, weight-average molecular weight $(M_w)$, and the polydispersities (PDI) of these polymers were in the range of 9000-58000, 27000-231000, 2.9-3.9, respectively. These polymers have quite good thermal stability with decomposition starting above 320-350. The polymers show photoluminescence (PL) with maximum peaks at around 526-562 nm (exciting wavelength, 410 nm) and blue EL with maximum peaks at around $\lambda_{max}$ = 526-552 nm. The current-voltageluminance (I-V-L) characteristics of polymers show turn-on voltages of 5 V. Even though both of EEPP-PPV and BEHP-PPV have the same terphenyl group in the repeating unit, EEPP-PPV with directly substituted alkoxy group in the back bone has longer effective conjugation length than BEHP-PPV, and exhibits red shift in the PL spectra. Both of EEPP-PPV and EHF-PPV have ter-phenyl units and directly substituted alkoxy group in back bone. EHF-PPV with fluorenyl unit attached to the PPV backbone has shorter effective conjugation length than EEPP-PPV with biphenyl unit, and exhibits blue shift in the PL spectra.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.237-244
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• 2017

Hyperbranched liquid crystalline polymers with azomesogenic and cholesteryl groups in their terminal positions were designed and synthesized by direct polycondensation reaction. The chemical structures and thermal and mesomorphic properties of the synthesized polymers were investigated by FT-IR, $^1H-NMR$, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), and polarizing optical microscopy (POM). The inherent viscosities (${\eta}_{inh}$) of the polymers were measured to be between 0.30 and 0.50 dL/g in phenol/p-chlorophenol/1,1,2,2-tetrachloroethane (25/40/35 = w/w/w). The degree of branching (DB) in these polymers ranged from 0.37 to 0.75; they, as amorphous polymer, showed glass transition temperatures ranging from 80 to $120^{\circ}C$; the polymers readily dissolved in most of the organic solvents used in the experiments. Only hyperbranched polymers with a cholesteryl group as their mesogenic group showed liquid crystalline phases.

• Polymer(Korea)
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• v.28 no.4
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• pp.314-320
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• 2004

Soluble aromatic polyimides bearing 4-(4-oxyalkyleneoxystyryl)- pyridines (ethylene and hexylene) as photoreactive side groups were synthesized and characterized. The photoreactive polymers were soluble in various polar organic solvents and their films were easily formed by solution casting. The photoreactivities of the polymers in the film state were approximately 64% at an exposure energy of 1.5 J/$\textrm{cm}^2$. Transmittances of the polymer films were about 85% after annealing at 20$0^{\circ}C$. Therefore, these polymers can be evaluated to be photoreactive polyimides with good transparency and solubility. The dichroic ratios of the polymers with ethylene and hexylene groups as the alkylene spacers were 0.023 and 0.026, respectively. The order parameters of 4'-pentyl-4-bipheny1carbonitrile as a liquid crystal (LC) in the film cells of the former and latter polymers were 0.50 and 0.52, respectively. These results indicate that the polymers show the effect of alkylene spacer on the photoalignments. The LC in the film cells of the polymers was perpendicularly oriented to the electric vector of the linear polarized UV light (LPUVL).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.86-92
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• 2019

Polymers with various compositions of azobenzene and hexamethylene groups in the main chain were synthesized by a Schotten-Baumann reaction and their properties were investigated. The chemical structures and physical properties of the synthesized polymers were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and x-ray diffraction. The polymers showed an inherent viscosity of 1.28-1.36 dl/g and were relatively insoluble in most organic solvents. The melt transition temperature increased rapidly with increasing number of azobenzene groups in the polymer. When the azobenzene monomer content was more than 50 mol%, no melting transition occurred below the decomposition temperature. Among the polymers with a melt transition temperature, the MP-A3C7 and MP-A5C5 polymers were liquid crystalline materials and exhibited a nematic phase with weak liquid crystallinity over a wide liquid crystal temperature range. This difference in the properties of the synthesized polymers is likely due to the changes in intermolecular forces resulting from the linearity and polarity of the trans-form of azobenzene.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.445-451
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• 2015

Semi-flexible liquid crystalline polymers containing a mesogenic group and an octamethylene flexible spacer in the main chain were synthesized by solution polycondensation. The mesogenic group in the polymer consists of four aromatic rings connected by ester and ketone, ether, sulfide, methylene, sulfone, or isopropylidene linkage groups. This paper discusses effects of the central linker of the mesogenic group on polymer properties. The structures and properties of synthesized polymers were investigated by $^1H$-NMR, FT-IR, differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), X-ray diffractometer (XRD), and polarizing optical microscope (POM). Polymers having bent linkage groups exhibited low thermal transition temperatures, narrow mesophase temperature ranges, low liquid crystallinity, and good solubilities in organic solvents, while those having bulky linkage groups were amorphous and exhibited high glass transition temperatures.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2419-2425
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• 2007

New poly(cyclopenta[def]phenanthrene) (PCPP)-based conjugated copolymers, containing carbazole units as pendants, were prepared as the electroluminescent (EL) layer in light-emitting diodes (LEDs) to show that most of them have higher maximum brightness and EL efficiency. The prepared polymers, Poly(2,6-(4-(6-(Ncarbazolyl)- hexyl)-4-octyl-4H-cyclopenta[def]phenanthrene)) (CzPCPP10) and Poly(2,6-(4-(6-(N-carbazolyl)- hexyl)-4-octyl-4H-cyclopenta[def]phenanthrene))-co-(2,6-(4,4-dioctyl-4H-cyclopenta[def]phenanthrene)) (CzPCPP7 and CzPCPP5), were soluble in common organic solvents and used as the EL layer in light-emitting diodes (LEDs) of configuration with ITO/PEDOT/polymer/Ca/Al device. The polymers are thermally stable with glass transition temperature (Tg) at 77-100 °C and decomposition temperature (Td) at 423-457 °C. The studies of cyclic voltammetry indicated same HOME levels in all polymers, although the ratios of carbazole units are different. In case of PLEDs with configuration of ITO/PEDOT/CzPCPPs/Ca/Al device, The EL maximum peaks were around 450 nm, which the turn-on voltages were about 6.0-6.5 V. The maximum luminescence of PLEDs using CzPCPP10 was over 4400 cd/m2 at 6.5 V, which all of the maximum EL efficiency were 0.12 cd/A. The CIE coordinates of the EL spectrum of PLEDs using CzPCPP10 was (0.18, 0.08), which are quite close to that of the standard blue (0.14, 0.08) of NTSC.

• Polymer(Korea)
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• v.29 no.4
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• pp.357-362
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• 2005

As a new class of electroluminescent (EL) polymers, PPV-based polymers containing sulfone group in the main chain were synthesized through Witting polymerization reaction to control n-conjugation length and energy levels for predictable light emission and enhanced device performance. These EL polymers showed good solubility in common organic solvents and high thermal stability with initial decomposition temperature of ca. $400^{circ}$ and glass transition temperature around $200^{circ}C$ Emission colors were tuned from green to deep blue by reducing ${\pi}$-conjugated length between sulfone groups. It was also noted from the cyclic voltammetry (CV) measurements and semiempirical calculations that sulfone group with high electron affinity effectively lowered HOMO-LUMO energy levels to enhance EL device performance.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.47-52
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• 2014

A series of liquid crystalline polyesters containing X-shaped mesogenic groups in main chain were synthesized through the solution polymerization of 2,5-di(4-substituted benzoate)hydroquinones and 4,4'-dicarboxy-1,8-diphenoxyoctane. The structures and properties of synthesized polymers were investigated by $^1H$-NMR, FT-IR, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), polarized optical microscopy (POM) and wide angel X-ray diffraction (WXRD). Inherent viscosities (${\eta}_{inh}$) of polymers were measured between 0.35 and 0.66 dL/g in 1,1,2,2-tetrachloroethane, and they were easily soluble in most of organic solvents used for this experiment. All polymers revealed relatively low melting transition temperature ($T_m$) and crystallinity, and also showed thermotropic nematic liquid crystallinity when they were heated to their melting temperatures. These properties of polymers were presumably due to the presence of the bulky substituting groups on the hydroquinone unit in mesogenic group.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.4130-4136
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• 2021

By polymerization of gadolinium methacrylate (Gd (MAA)₃), lead methacrylate (Pb(MAA)₂) and methyl methacrylate (MMA), Gd and Pb were chemically bonded into polymers. The X-ray shielding performance was evaluated by Monte Carlo simulation method, and the results showed that the more metal functional organic monomer, the better the shielding performance of terpolymers. When the X-ray energy is 65 keV, Gd (MAA)₃-containing polymers have better shielding performance than Pb(MAA)₂-containing polymers. Gd could compensate for the weak absorption region of Pb. Therefore, polymers containing both Gd and Pb enhanced shielding efficiency against X-ray in various low-energy ranges. For obtaining terpolymers with uniform monomer compositions, the relationship between the monomer composition of the terpolymers and the conversion level was optimized by calculating the reactivity ratios. The value of reactivity ratios of r (Gd (MAA)₃/Pb(MAA)₂), r (Pb(MAA)₂/Gd (MAA)₃), r (Gd (MAA)₃/MMA), r (MMA/Gd (MAA)₃), r (Pb(MAA)₂/MMA) and r (MMA/Pb(MAA)₂) was 0.483, 0.004, 0.338, 2.508, 0.255, 0.029. The terpolymers with uniform monomer composition could be obtained by controlling the monomer compositions or conversion levels. The results can provide new radiation protection materials and contribute to the improvement in nuclear safety.

• Textile Coloration and Finishing
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• v.35 no.1
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• pp.8-19
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• 2023

Silicone rubber is widely used in most industries due to diverse advantages like heat stability, UV stability, durability, chemical resistance, environment friendliness, inertness and so on. But there is limitation to expand applications due to relatively weak rubber strengths such as tensile strength and tear strength, especially in fabric coating applications. The purpose of this study is to find influence of coating agent on performances of rubber and coated fabrics and their correlation according to different crosslinking densities of silicone rubbers. Addition cure type of silicones were formulated using crosslinked MQ-type silicone resin consisting of M (R₃SiO_1/2) and Q (SiO_4/2) and linear polymers. Raw materials used were; 1) linear vinyl endblocked polymers and vinyl functional MQ resin as main polymers, 2) linear silicone hydride polymers as crosslinkers, 3) platinum catalyst and 4) inhibitor to control curing speed. Rubber specimens were prepared to check mechanical strength using universal testing machine (UTM). Crosslinking density was calculated using Flory-Rhener equation using solvent swelling method. Differential scanning calorimetry (DSC) and scanning electron microscope (SEM-EDS) were used to characterize rubbers. Consequently, it was found that physical properties of silicone rubbers and coated fabrics can be expected by crosslinking density of rubbers. Silicone rubber formulations that contain 20 ~ 30 wt% of vinyl MQ resin showed strongest balanced performances.