Small-Angle X-ray Scattering and Ultraviolet-Visible Spectroscopy Studies on the Structure and Structural Changes in Langmuir-Blodgett Films of Polyglutamates with Azobenzene Moieties Tethered by Alkyl Spacers of Different Length

Menzel, Henning; Weichart, B.; Schmidt, A.; Paul, Suvendu; Knoll, Wolfgang; Stumpe, Joachim; Fischer, Tony

doi:10.1021/la00018a052

Cited by 166 publications

(155 citation statements)

References 3 publications

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“…[22,23] Such a peak shift was observed for films of the polymers under investigation here (see Figure 6). …”

Section: Photo-induced Dichroismsupporting

confidence: 66%

“…Furthermore, the aggregation of the azobenzene leads to a deceleration of the E/Z-isomerization as was shown in previous investigations with well organized LangmuirBlodgett (LB) films. [21,23] A deceleration of the E/Z isomerization would result in fewer isomerization cycles taking place, and therefore in less effective formation of the SRG. The mechanism proposed here, for the restriction of the rotational and translational motion of azobenzene units by aggregation also explains the restriction of the azobenzene reorientation discussed above.…”

Section: Photo-induced Dichroismmentioning

confidence: 99%

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Novel Polymers to Study the Influence of the Azobenzene Content on the Photo‐Induced Surface Relief Grating Formation

Börger

Kuliskovska

G.-Hubmann

et al. 2005

Macro Chemistry & Physics

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Summary: The influence of the azobenzene concentration on the photo‐induced surface relief grating (SRG) formation in polymer films was investigated. Two series of polymers with 4‐alkoxy‐4′‐cyanoazobenzene side groups were synthesized. In series A, the degree of substitution was varied, while in series B, azobenzene and biphenyl groups were introduced in varying composition, but the concentration of non‐reacted HEMA‐groups was kept constant. Photo‐induction of the dichroism and the SRG was studied as function of the azobenzene concentration. An optimum was found for the SRG formation (76%), while the highest dichroism was induced at the lowest azobenzene concentration of 20%. The restriction of rotational and translational molecular motions observed at higher azobenzene concentration was explained by π‐π stacking of the azobenzene moieties and interaction of unreacted HEMA groups.

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“…[22,23] Such a peak shift was observed for films of the polymers under investigation here (see Figure 6). …”

Section: Photo-induced Dichroismsupporting

confidence: 66%

Section: Photo-induced Dichroismmentioning

confidence: 99%

Novel Polymers to Study the Influence of the Azobenzene Content on the Photo‐Induced Surface Relief Grating Formation

Börger

Kuliskovska

G.-Hubmann

et al. 2005

Macro Chemistry & Physics

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“…This result could be explained by H-aggregation of the molecules, which was correlated with the specifi c molecular packing structure. [ 18 ] In other words, the cyclohexylated molecules, CE4T and H-aggregation whereas the symmetric derivatives, DCE4T and DCB4T, tended to undergo J-aggregation. [ 14 ] We fabricated a thin-fi lm transistor using the synthesized materials as active layers.…”

Section: Uv-vis Absorption Spectroscopymentioning

confidence: 99%

H‐Aggregation Strategy in the Design of Molecular Semiconductors for Highly Reliable Organic Thin Film Transistors

Kim

Chen

et al. 2011

Adv Funct Materials

155

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IntroductionOver the past decade, several conjugated organic oligomers and polymers have been developed for potential use in low-cost semiconductor applications to replace their higher-cost inorganic counterparts. The most attractive aspect of these organic materials is that their structures can be diversifi ed and their physical or chemical properties tuned through strategic molecular design. [1][2][3][4][5][6][7][8][9] Among the variety of organic semiconductors developed, thiophene-based materials have emerged as an important class because of their high chemical and electrochemical stability, the accessibility of their preparation for thiophene synthesis, and the availability of welldeveloped/regioselective ring-ring coupling methodologies. [ 10 , 11 ] Furthermore, the properties of oligo/polythiophene cores can be effi ciently tuned by introducing appropriate substitutions. To date, the fi eld-effect transistor (FET) mobilities in devices composed of oligomeric thiophene semiconductors are generally higher than those obtained from conjugated polymers. Oligomeric thiophene semiconductor polymers engage in longrange packing, and effi cient charge transport is directly related to the long-range packing of molecules in semiconductor fi lms. Many synthetic methods have been developed to functionalize the α -and ω -ends of conjugated thiophene ring systems to increase the solubility and stability toward oxidation or to infl uence the solid-state ordering of oligothiophenes without affecting the planarity of the conjugated backbone. [ 12 , 13 ] The present study was devised based on the following three considerations: i) previously reported organic semiconductors have generally shown J-aggregation [ 14 ] with head-to-tail molecular stacking; [ 15 ] ii) large area π -stacking between adjacent molecules can be realized by H-aggregation, which occurs when molecules stack side by side; [ 16 ] and iii) H-aggregation induces stable morphologies in thin fi lms and reproducible transistor performances. We describe a novel synthetic strategy to induce H-aggregation between adjacent molecules in the thin fi lm state. We designed four types of quaterthiophene derivative with end-groups composed of cyclohexyl ethyl (CE4T), cyclohexyl butyl (CB4T), dicyclohexyl ethyl (DCE4T), and dicyclohexyl butyl (DCB4T). UV-vis absorption and grazing-incidence wideangle X-ray scattering (GIWAXS) analyses indicated that the asymmetric derivatives, CE4T and CB4T, tended to undergo H-Aggregation Strategy in the Design of Molecular Semiconductors for Highly Reliable Organic Thin Film TransistorsFour new quaterthiophene derivatives with end-groups composed of dicyclohexyl ethyl (DCE4T), dicyclohexyl butyl (DCB4T), cyclohexyl ethyl (CE4T), and cyclohexyl butyl (CB4T) were designed. All materials showed high solubility in common organic solvents. UV-vis absorption measurements showed that the quaterthiophene derivatives with asymmetrically substituted cyclohexyl end-groups (CE4T and CB4T) preferred H-type aggregation whereas those with symmetrica...

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“…[37] The spectra of the thin films can be fitted with Gaussian-type absorption bands, keeping all parameters constant except the amplitudes of the peaks. [37][38][39] The relative amounts of the chromophores in the different arrangements were determined as the areas of the corresponding peaks and are quoted as percentages in Figure 3. The peak fitting procedure is not a real quantitative determination but is a valuable tool to determine relative amounts of the aggregates.…”

Section: Full Papermentioning

confidence: 99%

Photoinduced Chiral Nematic Organization in an Achiral Glassy Nematic Azopolymer

Tejedor

Oriol

Serrano

et al. 2007

Adv Funct Materials

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A liquid crystalline homopolymer that has photoisomerizable methoxyazobenzene groups in the side chain has been synthesized and characterized. Thin films of the nematic glassy phase of this polymer have been processed in order to study the absorption spectra and the vibrational and electronic circular dichroism responses by irradiation with 488 nm circularly polarized light (CPL). Selective reflection of visible light demonstrates that the irradiation of this glassy nematic azopolymer induces a helix as a consequence of the chiral arrangement of the azobenzene units. Moreover, a wedge cell with an aligning layer for planar orientation was filled with the polymer with the aim of investigating the change in the macroscopic optical properties and optical textures of the azopolymer on irradiation with CPL. The transfer of chirality from CPL to azopolymer through chiral conformations is proposed as a model for explaining the supramolecular chirality.

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Small-Angle X-ray Scattering and Ultraviolet-Visible Spectroscopy Studies on the Structure and Structural Changes in Langmuir-Blodgett Films of Polyglutamates with Azobenzene Moieties Tethered by Alkyl Spacers of Different Length

Cited by 166 publications

References 3 publications

Novel Polymers to Study the Influence of the Azobenzene Content on the Photo‐Induced Surface Relief Grating Formation

Novel Polymers to Study the Influence of the Azobenzene Content on the Photo‐Induced Surface Relief Grating Formation

H‐Aggregation Strategy in the Design of Molecular Semiconductors for Highly Reliable Organic Thin Film Transistors

Photoinduced Chiral Nematic Organization in an Achiral Glassy Nematic Azopolymer

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