ortho-Phenylenes: Unusual Conjugated Oligomers with a Surprisingly Long Effective Conjugation Length

2010 ◽  
Vol 132 (39) ◽  
pp. 13848-13857 ◽  
Author(s):  
Jian He ◽  
Jason L. Crase ◽  
Shriya H. Wadumethrige ◽  
Khushabu Thakur ◽  
Lin Dai ◽  
...  
Keyword(s):  
Conjugated Oligomers ◽  
Conjugation Length ◽  
Effective Conjugation Length

Study on effect of supercritical CO2 on structural ordering and charge transporting property in thiophene-based block copolymer

2022 ◽  
Author(s):  
Satomi Hosokawa ◽  
Eri Tomita ◽  
Shinji Kanehashi ◽  
Kenji Ogino
Keyword(s):  
Supercritical Co2 ◽  
Hole Mobility ◽  
Amorphous Region ◽  
Crystalline Region ◽  
Space Charge Limited Current ◽  
Conjugation Length ◽  
Enhanced Mobility ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Effective Conjugation Length

Abstract We reported that supercritical (sc) annealing of poly(3-hexylthiophene) (P3HT), and its block copolymers with poly(ethylene oxide) (PEO) and polystyrene (PSt) brought about improvements in the crystal structure and hole mobility, determined by the space charge limited current (SCLC) measurement. P3HT-b-PEO showed the largest increase in mobility. From XRD profile, it was found that the treatment with scCO2 increased the crystallite size and crystallinity. UV-vis spectra showed that the effective conjugation length in the scCO2 treated films was increased compared to the as-spun, suggesting that CO2 molecules are incorporated into domains of the second block domains and P3HT amorphous region, and assist to alter the characteristics of the crystalline region. Then, it was considered that the change in the crystalline structure and the improvement of P3HT chains packing led to the enhanced mobility. Since PEO is known to have a higher affinity for CO2, the increase of mobility was specifically intensive.

Photoinduced Enhancement of Photoluminescence Intensity in PPV Films

2001 ◽  
Vol 665 ◽  
Author(s):  
Yara Galvão Gobato ◽  
Alexandre Marletta ◽  
Jucimar M. Souza ◽  
Ernesto Pereira ◽  
Roberto M. Faria ◽  
...  
Keyword(s):  
Laser Power ◽  
Blue Shift ◽  
Sample Thickness ◽  
Phenylene Vinylene ◽  
Photoluminescence Intensity ◽  
Carbonyl Groups ◽  
Conjugation Length ◽  
Ion Laser ◽  
Pl Intensity ◽  
Effective Conjugation Length

ABSTRACTPoly(p-phenylene vinylene) (PPV) films are usually photodegraded in air. We report on the enhancement of photoluminescence (PL) intensity of PPV films induced by Ar ion laser in the presence of air. The PL spectra were measured as function of laser power, time exposure and sample thickness. The initial PL intensity increases up to 300% without significant changes in peak positions by optimizing such parameters. This effect is accompanied by a blue-shift in the absorption spectrum resulting in shortened effective conjugation length and by a formation of defects such as carbonyl groups. Mechanisms for the observed photoluminescence intensity enhancements are suggested.

A Self-Threading Polythiophene: Defect-Free Insulated Molecular Wires Endowed with Long Effective Conjugation Length

2010 ◽  
Vol 132 (42) ◽  
pp. 14754-14756 ◽  
Author(s):  
Kazunori Sugiyasu ◽  
Yoshihito Honsho ◽  
Ryan M. Harrison ◽  
Akira Sato ◽  
Takeshi Yasuda ◽  
...  
Keyword(s):  
Molecular Wires ◽  
Conjugation Length ◽  
Effective Conjugation Length

scholarly journals Nonlinear correlations between ν1 Raman band and global scalar properties for different length carotenoids

2019 ◽  
Vol 58 (4) ◽  
Author(s):  
Mindaugas Mačernis
Keyword(s):  
Linear Dependence ◽  
Density Functional ◽  
Chemical Potential ◽  
Raman Band ◽  
Conjugation Length ◽  
Electrophilicity Index ◽  
Special Groups ◽  
Scalar Properties ◽  
Nonlinear Correlations ◽  
Effective Conjugation Length

The Raman ν1 band corresponding to the polarization of various length carotenoid (Car) and polyene molecules was theoretically analysed using the density functional theory (DFT) approach. The polarization and other properties of Car and polyene monomers were estimated by using global scalar properties. The results demonstrate a linear dependence between the frequency of the so-called ν1 Raman band corresponding to the C=C stretching modes, and the global hardness (and global softness) for all molecules of different conjugation lengths. Linear correlations between all global scalar properties and the conjugation length were for polyene structures only. From these calculations an additional relationship was also identified: upon s-cis-isomerisation the effective conjugation length and global softness increased for polyenes, while the effective conjugation length and global softness decreased for carotenoids containing β-rings at their ends. According to the electrophilicity index study, charge transfer processes (CT) should be favourable in longer carotenoid and polyene structures. A linear dependence of electronegativity was found for polyene and particular Cars subgroups. The electrophilicity index was very sensitive to special groups bonded to the polyene chain of Cars. Finally, the conjugation length of the Cars did not have a linear dependence on the electronegativity, chemical potential and electrophilicity index, but almost a linear dependence was seen on the global hardness while the polyene models had a linear dependence in all cases.

scholarly journals Doubly linked chiral phenanthrene oligomers for homogeneously π-extended helicenes with large effective conjugation length

2021 ◽  
Author(s):  
Yusuke Nakakuki ◽  
Takashi Hirose ◽  
Hikaru Sotome ◽  
Min Gao ◽  
Daiki Shimizu ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Dft Calculations ◽  
Conical Intersection ◽  
Molecular Devices ◽  
Nanometer Scale ◽  
Conjugation Length ◽  
Orbital Interactions ◽  
Nanocarbon Materials ◽  
Homo Lumo ◽  
Effective Conjugation Length

Helically twisted conductive nanocarbon materials are applicable to optoelectronic and electromagnetic molecular devices working on the nanometer scale. Herein, we report the synthesis of per-peri-perbenzo[5]- and [9]helicenes in addition to previously reported π-extended [7]helicene. The homogeneously π-extended helicenes can be regarded as helically fused oligo-phenanthrenes. The HOMO−LUMO gap decreased significantly from 2.14 to 1.15 eV with increasing helical length, suggesting the large effective conjugation length (ECL) of the π-extended helical framework. The large ECL of π-extended helicenes is attributed to the large orbital interactions between the phenanthrene subunits at the 9- and 10-positions, which form a polyene-like electronic structure. Based on the experimental results and DFT calculations, the ultrafast decay dynamics on the sub-picosecond timescale were attributed to the low-lying conical intersection.

Control of Effective Conjugation Length in Polyfluorene Thin Films

2006 ◽  
Vol 45 (No. 8) ◽  
pp. L247-L249 ◽  
Author(s):  
Kohei Asada ◽  
Takashi Kobayashi ◽  
Hiroyoshi Naito
Keyword(s):  
Thin Films ◽  
Conjugation Length ◽  
Effective Conjugation Length
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