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Jeong, Kwang-Un,Kim, Jang-Joo,Yoon, Tae-Ho The Polymer Society of Korea 2000 Korea polymer journal Vol.8 No.5
A novel diamine monomer, containing fluorine and phosphine oxide, bis(3-aminophenyl) 3,5-bis(trifluoromethyl)phenyl phosphine oxide (mDA6FPPO), was prepared via Grignard reaction, and utilized to prepare polyimides with dianhydrides such as PMDA, 6FDA, BTDA or ODPA, by the conventional two-step route; preparation of poly(amic acid), followed by solution imidization. The polyimides were characterized by FT-IR, NMR, and DSC with intrinsic viscosity and refractive index also being evaluated. A phosphine oxide containing monomer, bis(3-aminophenyl)phenyl phosphine oxide (mDAPPO) and a commercial 3,3-diaminodiphenyl sulfone (mDDS) were also used for comparison. The polyimides derived from mDA6FPPO exhibited high T$\sub$g/, excellent solubility and low birefringence.
Hierarchical Hybrid Nanostructures Constructed by Liquid Crystal Self-Assembly
Kwang-Un Jeong(정광운) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
By controlling the hierarchical nanostructures, we can develop advanced materials with the desired properties. For the construction of well-defined nanostructures of pristine [60]fullerene (C60) arrays, pyrene-based molecular tweezers (PT) were used as host molecules for arranging C60 guest molecules. The formation of host-guest complexes was studied in solution as well as in the solid state. Two-dimensional NMR studies revealed that host-guest complexes were related to the molecular self-assembly of PT. X-ray diffraction results exhibited the construction of well-defined layered nanostructures of the complexes. From electron mobility measurements, it was demonstrated that the well-defined nanostructure incorporating a C60 array exhibited a high electron mobility. This research demonstrated that chemical function transfer and shape amplification of programmed liquid crystal molecules allowed us to fabricate advanced materials with the desired properties on a macroscopic length scale.
Highly Thermal Conductive Alumina Plate/Epoxy Composite for Electronic Packaging
Jeong, Un Seong,Lee, Yoon Joo,Shin, Dong Geun,Lim, Hyung Mi,Mun, So Youn,Kwon, Woo Teck,Kim, Soo Ryong,Kim, Young Hee,Shim, Kwang Bo The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.6
In this study, alumina plates 9~25 μm in size were used as thermal fillers, and epoxy resin was used as a polymer matrix. Oriented alumina plate/epoxy composites were prepared using a rolling method. The effect of ordering alumina plates increased with alumina plate size. The thermal conductivity and flexural strength of the composites were investigated. The horizontal thermal conductivity of the oriented composite was significantly higher than the vertical thermal conductivity. The horizontal thermal conductivity of the 75 wt% alumina content was 8.78 W/mk, although the vertical thermal conductivity was 1.04 W/mk. Ordering of the alumina plate using a rolling method significantly improved the thermal conductivity in the horizontal direction. The flexural strengths of the ordered alumina/epoxy composites prepared at different curing temperatures were measured.
Jeong, Kwang-Un,Jang, Ji-Hyun,Kim, Dae-Yoon,Nah, Changwoon,Lee, Joong Hee,Lee, Myong-Hoon,Sun, Hao-Jan,Wang, Chien-Lung,Cheng, Stephen Z. D.,Thomas, Edwin L. Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.19
<P>Combining the physical principle of actuators with the basic concept of photonic crystals, colour-tunable three-dimensional (3D) photonic actuators were successfully fabricated. By controlling the <I>d</I>-spacings and the refractive index contrasts of the self-assembled 3D colloidal photonic crystals, colours of the photonic actuators were tuned. Various shapes of these 3D actuating objects were constructed by transforming the programmed 2D structures <I>via</I> bending, twisting and folding mechanisms. These 2D structures were first programmed by breaking the symmetry. The selective swellings were then applied as driving forces to control the shapes and colours of the photonic actuators. Scroll photonic actuators had been first demonstrated by bending the traditional 2D cantilever structure (K.-U. Jeong, <I>et al.</I>, <I>J.</I><I>Mater.</I><I>Chem.</I>, 2009, <B>19</B>, 1956). By breaking the symmetry of a cantilever structure perpendicular to its long axis, polypeptide-/DNA-like 3D helical photonic actuators were obtained from the programmed 2D structure <I>via</I> twisting processes. Both left- and right-handed scrolls and helices with various colours can be achieved by changing the polarity of solvents. Different types of 3D actuators, such as cube, pyramid and phlat ball, were also demonstrated <I>via</I> the folding mechanism. The reversible 3D photonic actuators transformed from the programmed 2D structures <I>via</I> the bending, twisting and folding mechanisms may be applied in the field of mechanical actuators, and optoelectronic and bio-mimetic devices.</P> <P>Graphic Abstract</P><P>Reversible colour and shape tunable photonic actuators were constructed by transforming the programmed 2D structures to the 3D objects <I>via</I> bending, twisting and folding mechanisms. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm03631e'> </P>
Colour-tunable spiral photonic actuators
Jeong, Kwang-Un,Jang, Ji-Hyun,Koh, Cheong Yang,Graham, Matthew J.,Jin, Kwang-Yong,Park, Soo-Jin,Nah, Changwoon,Lee, Myong-Hoon,Cheng, Stephen Z. D.,Thomas, Edwin L. Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.14
<P>Combining the multi-faceted environmental responsiveness of polymers with photonically active structures, we developed spiral photonic actuators which can reversibly change both shape and colour in response to the chemical environment.</P> <P>Graphic Abstract</P><P>Combining the multi-faceted environmental responsiveness of polymers with photonically active structures, we developed spiral photonic actuators which can reversibly change both shape and colour in response to the chemical environment. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b822980p'> </P>