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Park, Samdae,Kim, Kyungtae,Kim, Dong Min,Kwon, Wonsang,Choi, Junman,Ree, Moonhor American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.3
<P>A high temperature polyimide bearing anthracene moieties, poly(3,3′-di(9-anthracenemethoxy)-4,4′-biphenylene hexafluoroisopropylidenediphthalimide) (6F-HAB-AM PI) was synthesized. The polymer exhibits excellent thermal stability up to around 410 °C. This polymer is amorphous but orients preferentially in the plane of nanoscale thin films. In device fabrications of its nanoscale thin films with metal top and bottom electrodes, no diffusion of the metal atoms or ions between the polymer and electrodes was found; however, the aluminum bottom electrode had somewhat undergone oxide layer (about 1.2 nm thick) formation at the surface during the post polymer layer formation process, which was confirmed to have no significant influence on the device performance. The polymer thin film exhibited excellent unipolar and bipolar switching behaviors over a very small voltage range, less than ±2 V. Further, the PI films show repeatable writing, reading, and erasing ability with long reliability and high ON/OFF current ratio (up to 10<SUP>7</SUP>) in air ambient conditions as well as even at temperatures up to 200 °C.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-3/am101125d/production/images/medium/am-2010-01125d_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am101125d'>ACS Electronic Supporting Info</A></P>
Kim, Gahee,Park, Samdae,Jung, Jungwoon,Heo, Kyuyoung,Yoon, Jinhwan,Kim, Heesoo,Kim, Ik Jung,Kim, Jung Ran,Lee, Jong Im,Ree, Moonhor WILEY-VCH Verlag 2009 Advanced functional materials Vol.19 No.10
<P>New brush polymers with various numbers of bristle ends incorporating phosphorylcholine (PC) moieties are synthesized. The polymers are thermally stable up to 175 °C and form good-quality films with conventional spin-, roll-, and dip-coating, and subsequent drying processes. Interestingly, all these brush polymers, as a PC-containing polymer, demonstrate a stable molecular multi-bilayer structure in thin films that arise due to the efficient self-assembly of the bristles for temperatures <55 °C and PC-rich surfaces, and therefore successfully mimic natural cell-membrane surfaces. These brush-polymer films exhibit excellent water wettability and water sorption whilst retaining the remarkable molecular multi-bilayer structure, and thus have hydrophilic surfaces. These novel multi-bilayer structured films repel fibrinogen molecules and platelets from their surfaces but also have bactericidal effects on bacteria. Moreover, the brush-polymer films are found to provide comfortable surface environments for the successful anchoring and growth of HEp-2 cells, and to exhibit excellent biocompatibility in mice. These newly developed brush polymers are suitable for use in biomedical applications including medical devices and biosensors that require biocompatibility and the reduced possibility of post-operative infection.</P> <B>Graphic Abstract</B> <P>New brush polymers with various numbers of bristle ends incorporating phosphorylcholine (PC) moieties are synthesized. The new PC-containing brush polymers (see image) form a stable molecular multi-bilayer structure in thin films and successfully mimic natural cell membrane surfaces. The hydrophilic surface of the films repels fibrinogen and platelets and exhibit bactericidal effects. <img src='wiley_img/1616301X-2009-19-10-ADFM200801680-content.gif' alt='wiley_img/1616301X-2009-19-10-ADFM200801680-content'> </P>
Lee, Taek Joon,Chang, Cha-Wen,Hahm, Suk Gyu,Kim, Kyungtae,Park, Samdae,Kim, Dong Min,Kim, Jinchul,Kwon, Won-Sang,Liou, Guey-Sheng,Ree, Moonhor IOP Pub 2009 Nanotechnology Vol.20 No.13
<P>We have fabricated electrically programmable memory devices with thermally and dimensionally stable poly(<I>N</I>-(<I>N</I>′,<I>N</I>′-diphenyl-<I>N</I>′-1,4-phenyl)-<I>N</I>,<I>N</I>-4,4′-diphenylene hexafluoroisopropylidene-diphthalimide) (6F-2TPA PI) films and investigated their switching characteristics and reliability. 6F-2TPA PI films were found to reveal a conductivity of 1.0 × 10<SUP>−13</SUP>–1.0 × 10<SUP>−14</SUP> S cm<SUP>−1</SUP>. The 6F-2TPA PI films exhibit versatile memory characteristics that depend on the film thickness. All the PI films are initially present in the OFF state. The PI films with a thickness of >15 to <100 nm exhibit excellent write-once-read-many-times (WORM) (i.e. fuse-type) memory characteristics with and without polarity depending on the thickness. The WORM memory devices are electrically stable, even in air ambient, for a very long time. The devices’ ON/OFF current ratio is high, up to 10<SUP>10</SUP>. Therefore, these WORM memory devices can provide an efficient, low-cost means of permanent data storage. On the other hand, the 100 nm thick PI films exhibit excellent dynamic random access memory (DRAM) characteristics with polarity. The ON/OFF current ratio of the DRAM devices is as high as 10<SUP>11</SUP>. The observed electrical switching behaviors were found to be governed by trap-limited space-charge-limited conduction and local filament formation and further dependent on the differences between the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels of the PI film and the work functions of the top and bottom electrodes as well as the PI film thickness. In summary, the excellent memory properties of 6F-2TPA PI make it a promising candidate material for the low-cost mass production of high density and very stable digital nonvolatile WORM and volatile DRAM memory devices. </P>
Hahm, Suk Gyu,Choi, Seungchel,Hong, Sang-Hyun,Lee, Taek Joon,Park, Samdae,Kim, Dong Min,Kim, Jin Chul,Kwon, Wonsang,Kim, Kyungtae,Kim, Mee-Jung,Kim, Ohyun,Ree, Moonhor Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.15
<P>In this study, novel nonvolatile memory devices, based on a high performance polyimide, poly(3,3′-bis(diphenylcarbamyloxy)-4,4′-biphenylene hexafluoroisopropylidenediphthalimide) (6F-HAB-DPC PI), were fabricated with a simple conventional solution coating process. The devices were found to exhibit programmable, rewritable nonvolatile memory characteristics with a high ON/OFF current ratio of up to 10<SUP>9</SUP>, a long retention time in both ON and OFF states, and low power consumption. Moreover, the active 6F-HAB-DPC PI layer is thermally and dimensionally stable and thus hybridization with a complementary metal-oxide-semiconductor platform is feasible. The advantageous properties and ease of fabrication of the 6F-HAB-DPC PI based devices open up the possibility of the mass production of high performance digital nonvolatile polymer memory devices at low cost.</P> <P>Graphic Abstract</P><P>Electrical devices were fabricated with a thermally stable new polyimide. They reveal excellent memory characteristics, opening up the possibility of mass production of high performance nonvolatile memory devices at low cost. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b814470m'> </P>
Choi, Seungchel,Hong, Sang-Hyun,Cho, Shin Hyo,Park, Samdae,Park, Su-Moon,Kim, Ohyun,Ree, Moonhor WILEY-VCH Verlag 2008 Advanced Materials Vol.20 No.9
<B>Graphic Abstract</B> <P>Electrically programmable fuse-type polymer memory devices based on hyperbranched copper phthalocyanine polymer thin films are fabricated. The devices have novel write-once-read-many (WORM) memory characteristics, with a high ON/OFF current ratio (of 10<SUP>6</SUP>) and a high electrical stability, thus opening up the possibility of a low-cost mass production of high-performance, nonvolatile polymer memory devices. <img src='wiley_img/09359648-2008-20-9-ADMA200702147-content.gif' alt='wiley_img/09359648-2008-20-9-ADMA200702147-content'> </P>