• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.795-799
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• 2007

The bulk properties of poly(γ-benzyl-L-glutamate)-poly(ethylene glycol), PBLG-PEO, diblock copolymer were investigated. The helical transition from 7/2 to 13/5 for pure PBLG was at 120 oC while those of GE-1 and GE-2, which contain flexible PEO block 40 wt% and 60 wt% respectively, were shown at 135℃ on DSC experiments. FT-IR and XRD experiments were shown that the diblock copolymers maintained their α-helical structure in the temperature range between 25℃ and 175℃. Increasing relative size of coil part resulted in the increase of intermolecular packing distances. Due to well-maintained helical structure, lyotropic LC phases were observed for the PBLG-PEO block copolymer by the polarized optical microscope (POM). Especially, GE-3 copolymer, which has 12.5 wt% PEO contents, showed the smectic C phase. The competition of favorable aggregation energy between rod-rod and coil-coil, and unfavorable aggregation energy of rod-coil give rise to change the supramolecular structure in mixed solvent.

• Bulletin of the Korean Chemical Society
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• 제35권12호
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• pp.3590-3594
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• 2014

Blue phosphorescent $(dfpypy)_2Ir(mppy)$, where dfpypy = 2',6'-difluoro-2,3'-bipyridine and mppy = 5-methyl-2-phenylpyridine, has been synthesized by newly developed effective method and its solid state structure and photoluminescent properties are investigated. The glass-transition and decomposition temperature of the compound appear at $160^{\circ}C$ and $360^{\circ}C$, respectively. In a crystal packing structure, there are two kinds of intermolecular interactions such as hydrogen bonding ($C-H{\cdots}F$) and edge-to-face $C-H{\cdots}{\pi}(py)$ interaction. This compound emits bright blue phosphorescence with ${\lambda}_{max}=472nm$ and quantum efficiencies of 0.23 and 0.32 in fluid and the solid state. The emission band of the compound is red-shifted by 40 nm relative to homoleptic congener, $Ir(dfpypy)_3$. The ancillary ligand in $(dfpypy)_2Ir(mppy)$ has been found to significantly destabilize HOMO energy, compared to $Ir(dfpypy)_3$, $(dfpypy)_2Ir(acac)$ and $(dfpypy)_2Ir(dpm)$, without significantly changing LUMO energy.

• 폴리머
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• 제26권1호
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• pp.18-27
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• 2002

폴리벤조옥사졸 전구체로써 poly(ο-hydroxyamide)를 2,2'-bis(3-amino-4-hydroxy phenyl)hexafluoropropane과 여러 가지 bis-acid를 사용하여 축중합법에 의해 합성하였으며, 또한 이를 3,4-dihydro-2H-pyran과 부가반응시켜 산민감기인 tetrahydropyran이 부착된 방향족 폴리아미드를 합성하였다. Bis-acid의 구조에 따른 365 nm의 파장에서의 광투과도를 조사한 결과, 4,4'-oxydibenzoic acid로부터 합성된 중합체의 광투과도가 가장 우수하였다. 이러한 현상은 전자받게 성질을 갖고 있는 his-acid에 전자를 공여할 수 있는 구조를 도입하면 전자받게 성질이 감소되어 분자내 전하 이동 착물 (intra-CTC) 형성이 감소됨에 따라 광투과도가 증가된다고 사료된다. 또한 산민감기의 치환율이 높을수록 광투과도가 증가하는 경향을 보였다. 이는 방향족 폴리아미드에 산민감기인 THP의 치환율이 높아질수록 사슬과 사슬간의 조밀함이 떨어지기 때문에 분자간 전하 이동 착물 (inter-CTC) 형성을 줄여주는 효과를 얻게 되어 광투과도가 증가된다고 사료된다.