Co-reporter:Tomoya Fukui, Masayuki Takeuchi, Kazunori Sugiyasu
Polymer 2017 Volume 128(Volume 128) pp:
Publication Date(Web):16 October 2017
DOI:10.1016/j.polymer.2016.12.027
•Transformation kinetics of metastable supramolecular assembles was investigated.•We found that only a subtle alternation in molecular structure affects the kinetics.•We found that the size of the final outcome was determined kinetically.Molecular self-assembly under kinetic control has many opportunities leading to novel phenomena and applications. However, a mechanistic insight into the intricate kinetic behavior is still lacking. Herein, we demonstrate that even a subtle change in the molecular structure affects the kinetic behavior of metastable supramolecular assembles. Interestingly, the kinetic process influenced the size of the final outcomes (in this study, nanosheet structures) in a manner opposite to that predicted by the thermodynamic model. Our findings illustrate the difference between thermodynamically and kinetically controlled molecular self-assemblies. We believe that this study will expand the potential applications of molecular self-assemblies.Download high-res image (96KB)Download full-size image
Co-reporter:Mizuki Endo, Tomoya Fukui, Sung Ho Jung, Shiki Yagai, Masayuki Takeuchi, and Kazunori Sugiyasu
Journal of the American Chemical Society 2016 Volume 138(Issue 43) pp:14347-14353
Publication Date(Web):October 11, 2016
DOI:10.1021/jacs.6b08145
The significant contribution of conventional living polymerization to polymer science assures that living supramolecular polymerization will also lead to a variety of novel phenomena and applications. However, the monomer scope still remains limited in terms of the self-assembly energy landscape; a kinetic trap that retards spontaneous nucleation has to be coupled with a supramolecular polymerization pathway, which is challenging to achieve by molecular design. Herein, we report a rational approach to addressing this issue. We combined the supramolecular polymerization and photoisomerization processes to build the energy landscape, wherein the monomer can be activated/deactivated by light irradiation. In this way, the supramolecular polymerization and kinetic trap can be independently designed in the energy landscape. When the “dormant” monomer was activated by light in the presence of the seed of the supramolecular polymer, the “activated” free monomer was polymerized at the termini of the seed in a chain-growth manner. As a result, we achieved supramolecular polymers with controlled lengths and a narrow polydispersity. Although photoisomerization has been extensively employed in supramolecular polymer chemistry, most studies have focused on the stimuli responsiveness. In this respect, the present study would provoke supramolecular chemists to revisit stimuli-responsive supramolecular polymer systems as potential candidates for devising living supramolecular polymerization.
Co-reporter:Gábor Méhes, Chengjun Pan, Fatima Bencheikh, Li Zhao, Kazunori Sugiyasu, Masayuki Takeuchi, Jean-Charles Ribierre, and Chihaya Adachi
ACS Macro Letters 2016 Volume 5(Issue 7) pp:781
Publication Date(Web):June 13, 2016
DOI:10.1021/acsmacrolett.6b00205
We report on the realization of polymer light-emitting diodes (PLEDs) based on fluorescent polythiophene (PT)-based insulated molecular wires (IMWs). PLEDs using PT emitting layers traditionally have low external quantum efficiencies (ηeqe) below 0.1%. Moreover, IMWs lack a thorough exploitation for electroluminescent applications due to concerns about reduced charge transport between their chains. We constructed multilayer PLEDs containing PT IMW emitting layers that show the maximum ηeqe close to 1.4%, luminance at 3700 cd/m2, and low turn on voltage at 2.5 V. We also show a strong influence of the thickness of electron transport layer on ηeqe through device optimization and optical simulations.
Co-reporter:Manabu Kiguchi ; Tatsuhiko Ohto ; Shintaro Fujii ; Kazunori Sugiyasu ; Shigeto Nakajima ; Masayuki Takeuchi ;Hisao Nakamura
Journal of the American Chemical Society 2014 Volume 136(Issue 20) pp:7327-7332
Publication Date(Web):March 13, 2014
DOI:10.1021/ja413104g
A single molecular resistive (conductance) switch via control of anchoring positions was examined by using a molecule consisting of more than two same anchors. For this purpose, we adopted the covered quaterthiophene (QT)-based molecular wire junction. The QT-based wire consisted of two thiophene ring anchors on each side; thus, shift of anchors was potentially possible without a change in the binding modes and distortion of the intramolecular structure. We observed three distinct conductance states by using scanning tunneling microscope-based break junction technique. A detailed analysis of the experimental data and first-principles calculations revealed that the mechanism of the resistive switch could be explained by standard length dependence (exponential decay) of conductance. Here, the length is the distance between the anchoring points, i.e., length of the bridged π-conjugated backbone. Most importantly, this effective tunneling length was variable via only controlling the anchoring positions in the same molecule. Furthermore, we experimentally showed the possibility of a dynamic switch of anchoring positions by mechanical control. The results suggested a distinct strategy to design functional devices via contact engineering.
Co-reporter:Chengjun Pan, Kazunori Sugiyasu and Masayuki Takeuchi
Chemical Communications 2014 vol. 50(Issue 80) pp:11814-11817
Publication Date(Web):17 Jun 2014
DOI:10.1039/C4CC03594A
The fluorescence properties of conjugated polymer blends were investigated using a combination of excitation energy donor and acceptor conjugated polymers encapsulated by identical cyclic sidechains. Wearing this ‘uniform’, the polymers did not phase-separate in the blends. As such, these polymers provide an effective ensemble for designing fluorescent polymeric materials.
Co-reporter:Kazunori Sugiyasu, Soichiro Ogi and Masayuki Takeuchi
Polymer Journal 2014 46(10) pp:674-681
Publication Date(Web):August 6, 2014
DOI:10.1038/pj.2014.58
Inspired by functional systems in nature, chemists have created a number of intriguing and useful molecular systems from porphyrins and their metal complexes. Of the synthetic porphyrin derivatives developed to date, strapped porphyrins are unique because they have three-dimensional architectures based on a built-in two-dimensional porphyrin molecule. Consequently, the structures of strapped porphyrins can be customized through detailed molecular design, thereby allowing the synthesis of sophisticated molecular systems. Herein, we describe strapped porphyrin-based polymeric systems. In particular, we focus on molecular design concepts that are established in combination with photophysical, electronic and mechanical properties of polymeric materials.
Co-reporter:Chengjun Pan;Dr. Kazunori Sugiyasu;Dr. Junko Aimi;Akira Sato;Dr. Masayuki Takeuchi
Angewandte Chemie 2014 Volume 126( Issue 34) pp:9016-9021
Publication Date(Web):
DOI:10.1002/ange.201402813
Abstract
All-polythiophene diblock copolymers, comprising one unsheathed block and one fenced block, were synthesized through catalyst-transfer polycondensation. The unsheathed block self-assembles through π-π stacking, thereby inducing microphase separation. Consequently, we have succeeded in creating a microphase separation comprising an ensemble of stacked and isolated polythiophenes. This achievement could be extended to various unexplored applications as a result of the integration of the contrasting functions of the two blocks.
Co-reporter:Dr. Soichiro Ogi;Tomoya Fukui;Melinda L. Jue;Dr. Masayuki Takeuchi;Dr. Kazunori Sugiyasu
Angewandte Chemie International Edition 2014 Volume 53( Issue 52) pp:14363-14367
Publication Date(Web):
DOI:10.1002/anie.201407302
Abstract
Far-from-equilibrium thermodynamic systems that are established as a consequence of coupled equilibria are the origin of the complex behavior of biological systems. Therefore, research in supramolecular chemistry has recently been shifting emphasis from a thermodynamic standpoint to a kinetic one; however, control over the complex kinetic processes is still in its infancy. Herein, we report our attempt to control the time evolution of supramolecular assembly in a process in which the supramolecular assembly transforms from a J-aggregate to an H-aggregate over time. The transformation proceeds through a delicate interplay of these two aggregation pathways. We have succeeded in modulating the energy landscape of the respective aggregates by a rational molecular design. On the basis of this understanding of the energy landscape, programming of the time evolution was achieved through adjusting the balance between the coupled equilibria.
Co-reporter:Chengjun Pan;Dr. Kazunori Sugiyasu;Dr. Junko Aimi;Akira Sato;Dr. Masayuki Takeuchi
Angewandte Chemie International Edition 2014 Volume 53( Issue 34) pp:
Publication Date(Web):
DOI:10.1002/anie.201483471
Co-reporter:Chengjun Pan;Dr. Kazunori Sugiyasu;Dr. Junko Aimi;Akira Sato;Dr. Masayuki Takeuchi
Angewandte Chemie International Edition 2014 Volume 53( Issue 34) pp:8870-8875
Publication Date(Web):
DOI:10.1002/anie.201402813
Abstract
All-polythiophene diblock copolymers, comprising one unsheathed block and one fenced block, were synthesized through catalyst-transfer polycondensation. The unsheathed block self-assembles through π-π stacking, thereby inducing microphase separation. Consequently, we have succeeded in creating a microphase separation comprising an ensemble of stacked and isolated polythiophenes. This achievement could be extended to various unexplored applications as a result of the integration of the contrasting functions of the two blocks.
Co-reporter:Chengjun Pan;Dr. Kazunori Sugiyasu;Dr. Junko Aimi;Akira Sato;Dr. Masayuki Takeuchi
Angewandte Chemie 2014 Volume 126( Issue 34) pp:
Publication Date(Web):
DOI:10.1002/ange.201483471
Co-reporter:Chengjun Pan;Dr. Kazunori Sugiyasu;Dr. Yutaka Wakayama;Akira Sato;Dr. Masayuki Takeuchi
Angewandte Chemie 2013 Volume 125( Issue 41) pp:10975-10979
Publication Date(Web):
DOI:10.1002/ange.201305728
Co-reporter:Chengjun Pan;Dr. Kazunori Sugiyasu;Dr. Yutaka Wakayama;Akira Sato;Dr. Masayuki Takeuchi
Angewandte Chemie International Edition 2013 Volume 52( Issue 41) pp:10775-10779
Publication Date(Web):
DOI:10.1002/anie.201305728
Co-reporter:Soichiro Ogi, Kazunori Sugiyasu, and Masayuki Takeuchi
ACS Macro Letters 2012 Volume 1(Issue 10) pp:1199
Publication Date(Web):September 27, 2012
DOI:10.1021/mz300363j
We have synthesized a new entity of polymer structures composed of π-conjugated molecules: alternating donor–acceptor (D–A) copolymers featuring orthogonally arrayed transition dipoles along the polymer backbone. Such a unique structure could lead to novel functional fluorescent materials; therefore, we examined fluorescence resonance energy transfer (FRET) properties of the D–A copolymers using absorption, fluorescence, and fluorescence lifetime measurements based on the principle of FRET. The results suggested that the orthogonal and alternating D–A copolymer could potentially lead to a new FRET system in which the efficiency is sensitive to the polymer conformation.
Co-reporter:Yuki Ouchi;Dr. Kazunori Sugiyasu;Dr. Soichiro Ogi;Akira Sato;Dr. Masayuki Takeuchi
Chemistry – An Asian Journal 2012 Volume 7( Issue 1) pp:75-84
Publication Date(Web):
DOI:10.1002/asia.201100524
Abstract
We have recently reported a self-threading polythiophene as a new family of insulated molecular wires. Herein, we focused on the structure–property relationships of the unique three-dimensional architecture of the monomer. We have synthesized nine self-threading bithiophene monomers that have cyclic side-chains of different size and flexibility: i.e., 21-, 22-, 23-, 24-, 26-, and 30-membered rings composed of paraffinic, olefinic, or alkynic chains. To investigate their structure–property relationships, 1H NMR spectroscopy, UV absorption, and fluorescence spectroscopy measurements were conducted. We found that cyclic side-chains define the movable range of the dihedral angle of the bithiophene backbone, thereby affecting its photophysical properties. Therefore, the ability to design a structure with atomic precision as described herein would lead to the fine-tuning of the electronic properties of insulated molecular wires.
Co-reporter:Ryo Shomura, Kazunori Sugiyasu, Takeshi Yasuda, Akira Sato, and Masayuki Takeuchi
Macromolecules 2012 Volume 45(Issue 9) pp:3759-3771
Publication Date(Web):April 24, 2012
DOI:10.1021/ma300373n
In order to unveil the nature of charge carriers in a doped polythiophene, a sterically isolated polythiophenene, poly(1EDOT), was electrochemically synthesized on electrodes. Generation of charge carriers was induced upon controlled electrochemical doping and investigated through various spectroscopic methods; the charge carriers were identified based on spin concentration (ESR spectra), aromatic character (Raman spectra), and electronic transition (UV–vis–NIR absorption spectra) of the polythiophene. Peculiarity of this study lies in the fact that the electrochemistry of the poly(1EDOT) reflects the p-doping process of a single polythiophene wire because interwire interaction (i.e., π–π stacking) is effectively prevented; therefore, the results should be essential and informative to understand polythiophene-based materials and devices. Upon electrochemical doping, ESR active polarons were generated. Further doping concentrated the polarons, which led to the formation of polaron pairs. Eventually, the polaron pairs merged into bipolarons at the doping level of about 30–35%. Such a transformation of charge carriers under different doping levels has been extrapolated from studies using oligomeric model compounds. To the best of our knowledge, this is the first example addressing the nature of the charge carriers generated in a single polythiophene wire by exploiting the unique structure of the isolated polythiophene. Importantly, the comparison of poly(1EDOT) with common polythiophenes such as poly(3,4-ethylenedioxythiophene) (i.e., polyEDOT) implied that π–π stacking strongly affects the generation and stability of charge carriers. Furthermore, we found that the polaron pair plays an important role in charge hopping transport in the conduction mechanism.
Co-reporter:Kazunori Sugiyasu ; Yoshihito Honsho ; Ryan M. Harrison ; Akira Sato ; Takeshi Yasuda ; Shu Seki ;Masayuki Takeuchi
Journal of the American Chemical Society 2010 Volume 132(Issue 42) pp:14754-14756
Publication Date(Web):September 29, 2010
DOI:10.1021/ja107444m
Herein, we report on a self-threading polythiophene whose conjugated molecular wire is sheathed within its own cyclic side chains. The defect-free insulating layer prevents electronic cross-communication between the adjacent polythiophene backbone even in the solid film. Notably, the covalently linked cyclic side chains extend the effective conjugation length of the interior polythiophene backbone, which results in an excellent intrawire hole mobility of 0.9 cm2 V−1 s−1.
Co-reporter:Kazunori Sugiyasu Dr. ;Masayuki Takeuchi Dr.
Chemistry - A European Journal 2009 Volume 15( Issue 26) pp:6350-6362
Publication Date(Web):
DOI:10.1002/chem.200900576
Co-reporter:Chengjun Pan, Kazunori Sugiyasu and Masayuki Takeuchi
Chemical Communications 2014 - vol. 50(Issue 80) pp:NaN11817-11817
Publication Date(Web):2014/06/17
DOI:10.1039/C4CC03594A
The fluorescence properties of conjugated polymer blends were investigated using a combination of excitation energy donor and acceptor conjugated polymers encapsulated by identical cyclic sidechains. Wearing this ‘uniform’, the polymers did not phase-separate in the blends. As such, these polymers provide an effective ensemble for designing fluorescent polymeric materials.