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Synthesis and Characterization of Reversible Chemosensory Polymers: Modulation of Sensitivity through the Attachment of Novel Imidazole Pendants
(2012-12-01)
Satapathy, Rudrakanta
;
Padhy, Harihara
;
Wu, Yen-Hsing
;
Lin, Hong-Cheu
;
材料科學與工程學系
Three novel electron donoracceptor conjugated polymers (P1P3) bearing various imidazole pendants have been synthesized. Their excellent photophysical and electrochemical properties make them suitable transduction materials for chemosensing applications. Indeed, polymers P1P3 have been found to show remarkable sensing capabilities towards H+ and Fe2+ in semi-aqueous solutions. Upon titration with H+, polymers P1 and P2 showed hypsochromic shifts of their absorptions and photoluminescence (PL) maxima with enhanced fluorescence intensities. However, P3 showed diminished absorption and fluorescence intensities under similar conditions due to static quenching. The anomalous behavior of P3 compared with P1 and P2 has been clarified in terms of electronic distributions through computational analysis. Furthermore, P3 (KSV=1.03x107) showed a superior sensing ability towards Fe2+ compared with P1 (KSV=2.01x106) and P2 (KSV=4.12x106) due to its improved molecular wire effect. Correspondingly, the fluorescence lifetime of P3 was greatly decreased (almost 11-fold) compared to those of polymers P1 (4.6-fold) and P2 (6.2-fold) in the presence of Fe2+. By means of a fluorescence on-off-on approach, chemosensing reversibilities in protonationdeprotonation and metallationdemetallation have been achieved by employing triethylamine (TEA) and the disodium salt of ethylenediaminetetraacetic acid (Na2-EDTA)/phenanthroline, respectively, as suitable counter ligands. 1H NMR titrations have revealed the unique behavior of P3 compared with P1 and P2. To the best of our knowledge, there have been no previous reports of Fe2+ sensors based on single imidazole receptors conjugated to a main-chain polymer showing such a diverse sensitivity pattern depending on their attached substituents.
Synthesis, Characterization and Photophysical Properties of DCM-Based Light-Harvesting Dendrimers
(2011-04-15)
Vanjinathan, Mahalingam
;
Lin, Hong-Cheu
;
Nasar, A. Sultan
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A series of highly soluble light-harvesting dendrimers up to third generation were synthesized using a DCM-based core and Frechet-type benzyl ether dendrons containing pyrene end groups. All dendrimers and intermediates were characterized by FTIR, (1)H NMR, MALDI-TOF MS, UV-Vis, and PL spectra and EA, GPC, and TGA techniques. The dendrimers emit strong red PL around 570 nm. The excitation of the terminal chromophores results in core emission alone, as the donor emission is seriously quenched due to FRET to the core. The dendrimers showed enhanced luminescence properties of the core, and its efficiency was dependent on the generation number of the dendrimers. The above results reveal that these dendrimers are suitable candidates for red emissive materials in OLEDs.
Study of Supramolecular Side-Chain and Cross-Linking Polymers by Complexation of Various H-Donor Acids with H-Acceptor Copolymers Containing Pendent Carbazole and Fluorescent Pyridyl Units
(2009-06-01)
Liang, Tzung-Chi
;
Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Two H-bonded acceptor (H-acceptor) homopolymers 14 and 17 were successfully prepared by polymerization of fluorescent pyridyl monomers PBT and PBOT (12 and 13), which were synthesized via Sonogashira coupling and Wittig-Horner reactions. To increase the glass transition temperatures as well as reduce the pi-pi stacking of the photoluminescent (PL) H-acceptor copolymers and their H-bonded polymer complexes, fluorescent monomers 12 and 13 were copolymerized with N-vinylearbazole monomer CAZ (23) to produce H-acceptor copolymers 15-16 and 18-19. Supramolecular side-chain and crosslinking polymers (i.e., H-bonded polymer complexes) obtained by complexation of light-emitting H-acceptor polymers 14-19 with various proton donor (H-donor) acids 20-22 were further characterized by DSC, POM, FTIR, XRD, and PL measurements. The mesomorphic properties can be tuned from the nematic phase in H-acceptor homopolymers (14 and 17) to the tilted smectic C phase in their H-bonded polymer complexes (14/20-21 and 17/20-22) by the introduction of H-donor acids (20-22). Moreover, the PL properties of light-emitting H-acceptor polymers can be adjusted not only by the central structures of the conjugated pyridyl cores but also by their surrounding nonfluorescent H-donor acids. In general, redder shifts of PL emissions in H-bonded polymer complexes occurred when the light-emitting H-acceptor polymers were complexed with H-donors having smaller pKa values. (c) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2734-2753, 2009

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