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Jin, Young-Jae,Sakaguchi, Toshikazu,Teraguchi, Masahiro,Kwak, Giseop Informa UK (TaylorFrancis) 2017 MOLECULAR CRYSTALS AND LIQUID CRYSTALS - Vol.651 No.1
<P>Polydiphenylacetylene (PDPA) derivaitves consisting of different central atoms of C, Si, and Ge in the pendent group were comparatively investigated in normal, swollen, and acid-treated states. The Ge-containing PDPA was more emissive than the other two both in solution and in solid states. All the polymers showed emission enhancement in a swollen state: The PL quantum yields increased remarkably when swollen in an appropriate non-solvent. The Si and Ge atoms were easily removed from the polymer chain under acidic condition, as a result, the PL intensity was significantly decreased and the polymers turned to be insoluble in common organic solvents. Although the tert-butyl group of C-containing PDPA remained intact during the acid exposure, similar PL attenuation occurred.</P>
Kim, Beomsu Shin-Il,Jin, Young-Jae,Sakaguchi, Toshikazu,Lee, Wang-Eun,Kwak, Giseop American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.24
<P>This paper reports a unique fluorescence (FL) response and diverse applications of conjugated polyelectrolyte (CPE) through nonelectrostatic interaction with appropriate (bio)surfactants in an immiscible two-phase system. A sulfonated microporous conjugated polymer (SMCP) with a conformation-variable intramolecular stacked structure was used as the CPE film. Despite the extremely high hydrophilicity, the SMCP film responded significantly to the hydrophobic circumstances, either physicochemically or electronically, in the presence of water-in-oil (w/o)-type nonionic surfactants with appropriate hydrophile–lipophile balance (HLB) values. The polymer film became fully wet with hydrophobic solvents due to the addition of small amounts of (bio)surfactant to reveal remarkable FL emission enhancement and chromism. Microcontact and inkjet printing using the SMCP film (or SMCP-adsorbed paper) and the surfactant solution as substrate and ink, respectively, provided high-resolution FL images due to the distinctive surfactant-induced FL change (SIFC) characteristic. Moreover, the additional electrostatic interaction of SMCP film with oppositely charged surfactants further enhanced the FL emission. Our findings will help comprehensive understanding of the nonelectrostatic SIFC mechanism of CPEs and development of novel SIFC-active materials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-24/acsami.5b03717/production/images/medium/am-2015-037176_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b03717'>ACS Electronic Supporting Info</A></P>
Piezochromic fluorescence in liquid crystalline conjugated polymers
Lee, Wang-Eun,Lee, Chang-Lyoul,Sakaguchi, Toshikazu,Fujiki, Michiya,Kwak, Giseop Royal Society of Chemistry 2011 Chemical communications Vol.47 No.12
<P>Liquid crystalline diphenylacetylene polymer derivatives showed piezochromic fluorescence <I>via</I> order-to-disorder phase transition.</P> <P>Graphic Abstract</P><P>The liquid crystalline conjugated polymers showed piezochromic fluorescence whose emission colour was significantly changed by mechanical stress and then completely restored by solvent annealing. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc04811a'> </P>
Shin-Il Kim, Beomsu,Jin, Young-Jae,Uddin, Mohammad Afsar,Sakaguchi, Toshikazu,Woo, Han Young,Kwak, Giseop The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.71
<▼1><▼1><P>The polymer nanoparticles were readily transferred to the LFP to reveal highly distinguishable fluorescent images under the presence of surfactant with appropriate HLB value.</P></▼1><▼2><P>When aqueous conjugated-polyelectrolyte colloidal solutions containing an adequate amount of surfactant with an appropriate hydrophile–lipophile balance were sprayed onto latent fingerprints (LFPs), the polymer nanoparticles were readily transferred to the LFPs to reveal highly distinguishable fluorescent images, while the LFPs themselves remained intact.</P></▼2></▼1>
Seo, Kyo-Un,Jin, Young-Jae,Kim, Hyojin,Sakaguchi, Toshikazu,Kwak, Giseop American Chemical Society 2018 Macromolecules Vol.51 No.1
<P>Achiral poly(diphenylacetylene)s (PDPAs: pMe3, pEt3, piPr3, pMe2OD1, pMe2ODI, and mMe3) with different alkyl side chains at the para or meta position of the side phenyl ring were prepared to examine achiral-to-chiral transformations upon thermal annealing in a chiral solvent. All the para-substituted PDPAs showed significant circular dichroism (CD) enhancement upon annealing, whereas the meta-substituted polymer, mMe3, was inert to the same treatment. To investigate the kinetics, the asymmetric conformational change was monitored by observing the changes in the magnitude of circular polarization (g(CD)) or optical rotation. PDPAs with bulkier, round-shaped side groups (pEt3 and piPr3) had greater g(CD) values at equilibrium than pMe3 with a smaller side group. Moreover, the activation energy for the forward reaction (Ea(f)) was lower in the bulkier polymers than in pMe3 owing to enhanced miscibility with the chiral solvent. Similarly, the long alkyl chains of pMe2O1 and pMe2ODI acted as internal plasticizers to lower their Ea(f) values relative to that of pMe3, whereas their g(CD) values at equilibrium were smaller than that of pMe3. The kinetics of the achiral-to-chiral transformation is discussed in detail based on the spectroscopic changes observed during the annealing process.</P>
Solvent-to-Polymer Chirality Transfer in Intramolecular Stack Structure
Lee, Daehoon,Jin, Young-Jae,Kim, Hyojin,Suzuki, Nozomu,Fujiki, Michiya,Sakaguchi, Toshikazu,Kim, Seog K.,Lee, Wang-Eun,Kwak, Giseop American Chemical Society 2012 Macromolecules Vol.45 No.13
<P>Solvent-to-polymer chirality transfer was examined using conjugated polymer with intramolecular stack structure (IaSS). When achiral poly(diphenylacetylene)s (PDPAs) dissolved in limonene, the solvent chirality was successfully transferred to the side phenyl stack structure, leading to intramolecular axial chirality. The phenyl–phenyl IaSS was under thermodynamic control to readily undergo asymmetric changes in chiral limonene, leading to optical activity in the isotropic structure between the main chain and resonant side phenyl rings. The axial chirality was significantly affected by the chain length and substitution position of the side alkyl groups. The longer alkyl chains and bulkier alkyl group prevented direct intermolecular interactions between the side phenyl rings and the chiral limonene molecules. PDPA with sterically congested, highly stable, and regulated IaSS was not favorable for efficient solvent-to-polymer chirality transfer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2012/mamobx.2012.45.issue-13/ma300976r/production/images/medium/ma-2012-00976r_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma300976r'>ACS Electronic Supporting Info</A></P>
Lee, Wang-Eun,Oh, Chang-Jin,Park, Guen-Tae,Kim, Jin-Woo,Choi, Heung-Jin,Sakaguchi, Toshikazu,Fujiki, Michiya,Nakao, Ayako,Shinohara, Ken-ichi,Kwak, Giseop Royal Society of Chemistry 2010 Chemical communications Vol.46 No.35
<P>The significant variation in photoluminescence emission of poly(diphenylacetylene) derivatives according to the substitution position is due to the differences in the intramolecular π-stack structure and chain conformation.</P> <P>Graphic Abstract</P><P>The emission and chain conformation of poly(diphenylacetylene) derivatives are significantly influenced by the substitution position of trimethylsilyl group on the side phenyl ring. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc01481h'> </P>
Lee, Wang-Eun,Jin, Young-Jae,Kim, Shin-Il,Kwak, Giseop,Kim, Joon Heon,Sakaguchi, Toshikazu,Lee, Chang-Lyoul The Royal Society of Chemistry 2013 Chemical communications Vol.49 No.84
<P>An anionic conjugated polyelectrolyte based on polydiphenylacetylene showed a significant fluorescence turn-on response to positively-charged proteins through a conformational relaxation of its intramolecular stack structure.</P> <P>Graphic Abstract</P><P>An anionic conjugated polyelectrolyte based on polydiphenylacetylene showed a significant fluorescence turn-on response to positively-charged proteins through a conformational relaxation of its intramolecular stack structure. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cc45538f'> </P>