• Macromolecular Research
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• v.17 no.5
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• pp.313-318
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• 2009

The side chain liquid crystal triblock copolymers (TBCs), which underwent phase transitions below their decomposition temperature, were prepared by copolymerization of poly(n-butyl acrylate) and a comonomer containing the mesogenic azobenzene group. The physical properties of TBCs in the distinctive transition temperature ranges were investigated in terms of the liquid crystal (LC) content in the copolymers. The phase transition temperatures traced optically, thermally and rheologically were well coincided one another and clearly exhibited the phase transition of smectic-nematic-isotropic with increasing temperature. In the smectic phase, increasing temperature made the liquid crystal system more elastic, but viscosity (${\eta}'$) remained almost constant. In the nematic phase, increasing temperature abruptly decreased ${\eta}'$ and G', ultimately leading to isotropic phase. Both smectic and nematic phases exhibited Bingham viscosity behavior but the former gave much greater yield stress at the same LC content.

• Journal of Photoscience
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• v.12 no.2
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• pp.95-100
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• 2005

We have synthesized an azobenzene-containing polymer (PEA) and a stilbene-containing polymer (PAS) with second-order nonlinear properties. The second harmonic coefficient ($d_{33}$) of the poled polymer films was 84 and 36 pm/V for of PEA and PAS, respectively. The poled state of these polymers was stable at least up to 30 h at room temperature. $T_g$ of these polymers appeared in the range from 120 to $160^{\circ}C$ and onset of initial weight losses in the range from 260 to $270^{\circ}C$. Silicon moieties in the main chain enhanced the solubility of PEA and PAS in common organic solvents such as chloroform, N-methylpyrrolidinone (NMP), N, N-dimethylformamide (DMF), etc.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.182-185
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• 2001

The functionlized dendrimer containing 48 azobenzene was synthesized. Many isolated featureless domains were explicitly observed even at the air-water interface. Also, these monolayers were representatively observed, showing the change of surface pressure with irradiation time and wavelength. In AFM images. the larger domains irregularly shaped structures on the top while the smaller ones were free from such defects. In the optical absorption spectra of the LB films by UV irradiation and heat treatment, only photoisomerization of the G4-48Az monolayers was observed, a decrease of absorbance peak without change of the spectral shape. This suggests that optical behavior and morphological change are affected by the functional group and the symmetric chain.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.25-26
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• 2006

Azobenzene functionalized polymers have been extensively investigated due to the potential applications in the areas of optical switching, optical elements, optical information storage, and nonlinear optics. These applications are mainly achievable due to photoinduced properties of azobenzene groups with photoisomerization and photoinduced anisotropy. We report applications to the optoelectronic devices using inscribed one-(1D) and two-dimensional (2D) SRGs on azo polymer films. The inscribed holographic SRGs patterns were useful to control or enhance optoelectronic properties such as transparent electrode patterning, hybrid solar cell and ultraviolet GaN-based LED.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.169-169
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• 2006

Novel liquid crystalline malonic ester monomers were synthesized from malonyl dichloride and mesogenic alcohols as a photoresponsive group. The monomers were polymerized with aliphatic or aromatic dibromides in the presence of sodium hydride to give 8 kinds of novel poly(malonic esters) with two symmetrical azobenzene groups. We found that the resulting polymer films could be used as rewritable optical data storage (or holographic image) media through a photoisomerization of azobenzene group by Ar laser irradiation. The sensitivity of data recording was dependent not only on the thickness of the polymeric thin film but also on the intensity of laser beam.

• Fibers and Polymers
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• v.2 no.1
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• pp.123-130
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• 2001

Photoresponsive side chain copolymer and homopolymer containing an aminonitroazobenzene were synthesized for studying photoisomerization behavior and photo-induced anisotropy. Trans-to-cis photoisomerization was observed under the exposure of a circularly polarized visible light with UV-Vis absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532nm. Polarized absorption spectroscopy was employed to investigate the anisotropy of the polymer film during irradiationg of the excitation light. Layers of two photosensitive polymers were used for aligning liquid crystal(LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.34-37
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• 2002

Freestanding azobenzene-containing liquidcrystalline network (LCN) films. with macroscopic uniaxial molecular alignment were prepared by insitu photopolymerization. By polarizing microscopy, fiber-like structures aligned in one direction were observed. Furthermore, with a confocal laser scanning microscope (CLSM), it was confirmed that the fiber-like structures were formed even in the bulk of the LCNs. Upon UV light irradiation to cause trans-cis photoisomerization of the azobenzene molecules, the LCNfilms underwent a significant and anisotropic bending toward the irradiation direction of UV light. When the bent LCNfilms were exposed to Vis light, unbending of the LCN films immediately took place and the initial flat LCN films were restored. This bending and unbending behavior of the LCN films could be repeated just by changing the wavelength of the irradiation light. It was suggested that the bending was induced by an absorption gradient which produced a volume difference between the front surface area and the bulk of the network films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.38-42
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• 1996

The pressure-area isotherm of monolayer at the air-water interface were obtained and the LB films were fabricated onto a quartz slides and quartz crystal by conventional Langmuir-Blodggett(LB) method. The UV absorption spectra of Langmuir-Blodggett(LB) film on quartz slides and spectrum of monolayer formed on quartz crystal have been measured. The photoisomerization of the long-chain fatty avid containing azobenzene were obtained by the application of UV and visible light. The reversibility of photoisomerization were more clear difference when the number of C$\_$n/ increased. At the pressure-area isotherms, the value of surface pressure increment were decreased when the number of C$\_$n/ increased, A surface pressure of 20mN/m was obtained as a proper one for a film deposition. The photoisomerization at LB films were also obtained by application of UV and visible light. So the LB film of long-chain fatty acid containing azobenzene has possibility to being applies to functional molecular devices such as photomemory and light switching.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.552-561
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• 1994

The cis → trans thermal isomerization of azobenzene derivatives has been studied. A sizable solvent effect on the rates for thermal isomerization of push-pull azobenzenes are observed. It is suggested that the isomerization proceeds via a rotational mechanism. For non push-pull azobenzenes, the lack of solvent effects on the rate of isomerization was observed. This suggests that the isomerization proceeds via an inversional mechanism for non push-pull azobenzenes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.283-286
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• 2000

In this paper, generation form of displacement current was compared and measured induce monolayers which 8A5H with Pure azobenzene. Light response of two monolayers which compared and measured though they are the same isomer. The experimental results are as following; In case of ultraviolet($\lambda_1$) and visible($\lambda_2$) irradiation on 8A5H induce monolayers depositioned on board the peak of current was detected about 10[fA]. but light irradiation on pure azobenzene any particular reaction for detailed. This is the reason of hydrophobicity construct in molecule structures its molecule dynamic behaviour in cis and trans was not due to activated.