http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Kwon, Min Sang,Gierschner, Johannes,Yoon, Seong‐,Jun,Park, Soo Young WILEY‐VCH Verlag 2012 Advanced Materials Vol.24 No.40
<P><B>A novel donor–acceptor–donor triad that exhibits fluorescence on–off switching</B> with high contrast ratio (ca. 10<SUP>3</SUP>) in response to a mechanical stimulus in the solid state is reported. This system provides a very unique example of high‐contrast fluorescence switching that is driven by a mechanical‐force‐controlled photo‐induced electron transfer (eT) in molecular assemblies.</P>
Park, Sang Kyu,Cho, Illhun,Gierschner, Johannes,Kim, Jin Hong,Kim, Jong H.,Kwon, Ji Eon,Kwon, Oh Kyu,Whang, Dong Ryeol,Park, Jung‐,Hwa,An, Byeong‐,Kwan,Park, Soo Young WILEY‐VCH Verlag 2016 Angewandte Chemie Vol.55 No.1
<P><B>Abstract</B></P><P>We report on a molecularly tailored 1:1 donor–acceptor (D‐A) charge‐transfer (CT) cocrystal that manifests strongly red‐shifted CT luminescence characteristics, as well as noteworthy reconfigurable self‐assembling behaviors. A loosely packed molecular organization is obtained as a consequence of the noncentrosymmetric chemical structure of molecule <B>A1</B>, which gives rise to considerable free volume and weak intermolecular interactions. The stacking features of the CT complex result in an external stimuli‐responsive molecular stacking reorganization between the mixed and demixed phases of the D‐A pair. Accordingly, high‐contrast fluorescence switching (red↔blue) is realized on the basis of the strong alternation of the electronic properties between the mixed and demixed phases. A combination of structural, spectroscopic, and computational studies reveal the underlying mechanism of this stimuli‐responsive behavior.</P>
Yoon, Seong-Jun,Chung, Jong Won,Gierschner, Johannes,Kim, Kil Suk,Choi, Moon-Gun,Kim, Dongho,Park, Soo Young American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.39
<P>Color tuning and switching of the solid-state luminescence of organic materials are attractive subjects for both the fundamental research and practical applications such as optical recording. We report herein cyanostilbene-based highly luminescent molecular sheets which exhibit two-color fluorescence switching in response to pressure, temperature, and solvent vapor. The origin for the multistimuli luminescence switching is the two-directional shear-sliding capability of molecular sheets, which are formed via intermolecular multiple C−H···N and C−H···O hydrogen bonds. The resulting two distinctive crystal phases are promoted by different modes of local dipole coupling, which cause a substantial alternation of π−π overlap. These changes can be directly correlated with the subsequent intermolecular excitonic and excimeric coupling in both phases, as demonstrated by an in-depth theory-assisted spectroscopic and structural study. Finally, we have prepared a first device demonstrator for rewritable fluorescent optical recording media which showed multistimuli luminescence tuning with fast response. Our multistimuli responsive system is unique in terms of the slip-stacking of molecular sheets and thus provides a novel concept of rewritable fluorescent optical recording media.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-39/ja1044665/production/images/medium/ja-2010-044665_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja1044665'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja1044665'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja1044665'>ACS Electronic Supporting Info</A></P>
백종호,권용환,Juan Carlos Roldao,유영창,김현중,Johannes Gierschner,이원주,권민상 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
Solvent-free light-curing acrylic pressure-sensitive adhesives (PSAs) have tremendously grown but mostly prepared in the presence of photo initiators by high-energy UV-light that causes several issues such as radiation safety. Herein, for the first time, solvent-free acrylic PSAs were prepared through visible-light-driven photocatalytic free radical polymerization. Combined experimental and theoretical studies show that the use of N-vinyl based monomer is essential to enhance the polymerization rate and monomer conversion. Viscoelasticity, mechanical strength and adhesion performance of acrylic PSAs were nicely adjusted in a broad range by controlling the monomer composition, suggesting that our new method would replace the existing photoinitiated free radical polymerization.
Kwon, M.,Jordahl, J.,Phillips, A.,Chung, K.,Lee, S.,Gierschner, J.,Lahann, J.,Kim, J. THE ROYAL SOCIETY OF CHEMISTRY 2016 Chemical Science Vol.7 No.3
<P>Metal-free organic phosphors can be an attractive smart optical sensing materials since, in such compounds, intersystem crossing (ISC) and the phosphorescence process are placed in subtle competition with fluorescence, internal conversion (IC), and non-radiative decay pathways. Here, we report a unique environment-dependent multi-luminescence switching behavior of metal-free organic phosphorescent materials. Through combined photophysical measurements and computational electronic structure analysis, we systematically investigated how physicochemical properties of organic solvents affect the photophysical pathways of the metal-free organic phosphors. By rationally adapting the finding into phosphor-doped electrospun polymer fibers, we developed a new luminometric sensory platform and achieved selective detection of eight different common organic solvents. The presented finding provides new possibilities for metal-free organic phosphors to be a novel class of smart optical sensory materials.</P>
Shear-Triggered Crystallization and Light Emission of a Thermally Stable Organic Supercooled Liquid
Chung, Kyeongwoon,Kwon, Min Sang,Leung, Brendan M.,Wong-Foy, Antek G.,Kim, Min Su,Kim, Jeongyong,Takayama, Shuichi,Gierschner, Johannes,Matzger, Adam J.,Kim, Jinsang American Chemical Society 2015 ACS central science Vol.1 No.2
<▼1><P/><P>Thermodynamics drive crystalline organic molecules to be crystallized at temperatures below their melting point. Even though molecules can form supercooled liquids by rapid cooling, crystalline organic materials readily undergo a phase transformation to an energetically favorable crystalline phase upon subsequent heat treatment. Opposite to this general observation, here, we report molecular design of thermally stable supercooled liquid of diketopyrrolopyrrole (DPP) derivatives and their intriguing shear-triggered crystallization with dramatic optical property changes. Molten DPP8, one of the DPP derivatives, remains as stable supercooled liquid without crystallization through subsequent thermal cycles. More interestingly, under shear conditions, this supercooled liquid DPP8 transforms to its crystal phase accompanied by a 25-fold increase in photoluminescence (PL) quantum efficiency and a color change. By systematic investigation on supercooled liquid formation of crystalline DPP derivatives and their correlation with chemical structures, we reveal that the origin of this thermally stable supercooled liquid is a subtle force balance between aromatic interactions among the core units and van der Waals interactions among the aliphatic side chains acting in opposite directions. Moreover, by applying shear force to a supercooled liquid DPP8 film at different temperatures, we demonstrated direct writing of fluorescent patterns and propagating fluorescence amplification, respectively. Shear-triggered crystallization of DPP8 is further achieved even by living cell attachment and spreading, demonstrating the high sensitivity of the shear-triggered crystallization which is about 6 orders of magnitude more sensitive than typical mechanochromism observed in organic materials.</P></▼1><▼2><P>We investigate the molecular origin behind the shear-triggered crystallization with dramatic optical property changes of a thermally stable supercooled liquid.</P></▼2>
Park, Sang Kyu,Varghese, Shinto,Kim, Jong H.,Yoon, Seong-Jun,Kwon, Oh Kyu,An, Byeong-Kwan,Gierschner, Johannes,Park, Soo Young American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.12
<P>We have rationally designed a densely packed 1:1 donor–acceptor (<B>D</B>–<B>A</B>) cocrystal system comprising two isometric distyrylbenzene- and dicyanodistyrylbenzene-based molecules, forming regular one-dimensional mixed stacks. The crystal exhibits strongly red-shifted, bright photoluminescence originating from an intermolecular charge-transfer state. The peculiar electronic situation gives rise to high and ambipolar p-/n-type field-effect mobility up to 6.7 × 10<SUP>–3</SUP> and 6.7 × 10<SUP>–2</SUP> cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP>, respectively, as observed in single-crystalline OFETs prepared via solvent vapor annealing process. The unique combination of favorable electric and optical properties arising from an appropriate design concept of isometric <B>D</B>–<B>A</B> cocrystal has been demonstrated as a promising candidate for next generation (opto-)electronic materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-12/ja312197b/production/images/medium/ja-2012-12197b_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja312197b'>ACS Electronic Supporting Info</A></P>
Song, Yuna,Kim, Youngmu,Noh, Yeonjin,Singh, Varun Kumar,Behera, Santosh Kumar,Abudulimu, Abasi,Chung, Kyeongwoon,Wannemacher, Reinhold,Gierschner, Johannes,Lü,er, Larry,Kwon, Min Sang American Chemical Society 2019 Macromolecules Vol.52 No.15
<P>A highly efficient organic photocatalyst (OPC) for photoinduced electron/energy-transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization was identified through a systematic catalyst design and discovery. The devised OPC offers excellent control over PET-RAFT polymerizations of methyl methacrylate at very low catalyst loadings (5 ppm), that is, ca. 5-50 times lower loadings than other OPCs reported so far. Moreover, excellent oxygen tolerance was achieved using the discovered OPC combined with trithiocarbonate-based chain-transfer agent (CTA) under low-energy light irradiation conditions. In depth experimental and computational investigations revealed that (1) strong visible-light absorption and efficient generation of long-lived triplet states of the OPC due to its unique molecular structure and (2) the oxidation stability and no rate retardation of trithiocarbonate-based CTA are the key to the outstanding oxygen tolerance and ppm-level catalyst loadings. Our approach is thus believed to address a variety of challenging tasks related to polymer synthesis and living additive manufacturing.</P> [FIG OMISSION]</BR>