Supramolecular ordered photochromic cholesteric polymers as smart labels for thermal monitoring applications

Benelli, Tiziana; Mazzocchetti, Laura; Mazzotti, Giovanni; Paris, Fabio; Salatelli, Elisabetta; Giorgini, Loris

doi:10.1016/j.dyepig.2015.11.009

Cited by 8 publications

(5 citation statements)

References 37 publications

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“…521 In this latter study, the authors excluded LD and LB contributions to the measured ECD signals by sample rotation and displacement. Many other azobenzene-functionalized polymethacrylates have been investigated, bearing several enantiopure groups in the side chains as source of chirality: pyrrolidine, 522,523 prolinol, 524 hydroxysuccinimide 525 or (+)-L-lactate 526 bridges, as well as cholesteryl 527 and branched alkyl 528−532 substituents. Most of them revealed a liquid crystal behavior, with a supramolecular order (and chiroptical properties) very sensitive to temperature and light irradiation processes.…”

Section: Ecd In Thin Films Of π-Conjugated Oligomers and Polymersmentioning

confidence: 99%

“…Many other azobenzene-functionalized polymethacrylates have been investigated, bearing several enantiopure groups in the side chains as source of chirality: pyrrolidine, , prolinol, hydroxysuccinimide or (+)- l -lactate bridges, as well as cholesteryl and branched alkyl − substituents. Most of them revealed a liquid crystal behavior, with a supramolecular order (and chiroptical properties) very sensitive to temperature and light irradiation processes. − Furthermore, some examples of achiral polymethacrylates liquid crystals with azobenzene − or azo-binaphthyl chromophores showing induced ECD only after CP-light irradiation were also described; in particular, CP-light-induced supramolecular chirality was also testified via SHG-CD measurements in thin films of the achiral azobenzene polymethacrylate poly(DR1M) .…”

Section: Ecd Properties In Thin Films Of π-Conjugated Systems: Litera...mentioning

confidence: 99%

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Chiroptical Properties in Thin Films of π-Conjugated Systems

2020

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Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecular structures and intermolecular interactions to a large extent. Electronic circular dichroism, ECD, and its emission counterpart, circularly polarized luminescence, CPL, provide tools for studying aggregated states and the key properties to be sought for designing innovative devices. In this review, we shall present a comprehensive coverage of chiroptical properties measured on thin films of organic π-conjugated molecules. In the first part, we shall discuss some general concepts of ECD, CPL, and other chiroptical spectroscopies, with a focus on their applications to thin film samples. In the following, we will overview the existing literature on chiral π-conjugated systems whose thin films have been characterized by ECD and/or CPL, as well other chiroptical spectroscopies. Special emphasis will be put on systems with large dissymmetry factors (g abs and g lum) and on the application of ECD and CPL to derive structural information on aggregated states.

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Section: Ecd In Thin Films Of π-Conjugated Oligomers and Polymersmentioning

confidence: 99%

Section: Ecd Properties In Thin Films Of π-Conjugated Systems: Litera...mentioning

confidence: 99%

Chiroptical Properties in Thin Films of π-Conjugated Systems

2020

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“…Azobenzenes attached as side chains to covalent polymers have shown chiroptical switching. [ 27–31 ] Whereas efficient photoswitching has often been observed in these materials, they lack the cooperative trigger to induce changes at a mesoscopic length scale due to: i) the low local density of photoactive molecules, ii) the often random organization and flexibility of the polymer main chain, and iii) the presence of flexible spacers between the mesogens (azobenzene) and the main chain. Azobenzenes in direct conjugation with an electronically active polymer backbones can lead to significant structural reorganization, [ 32–35 ] which offers the possibility of tuning the electronic properties of the polymer by employing the state of polarization of light.…”

Section: Figurementioning

confidence: 99%

Consequences of Chirality in Directing the Pathway of Cholesteric Helix Inversion of π‐Conjugated Polymers by Light

et al. 2020

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Control over main‐chain motion of chiral π‐conjugated polymers can lead to unexpected new functionalities. Here, it is shown that by combining photoswitchable azobenzene units in conjugation with chiral fluorene comonomers and appropriate plasticizers, the polymer organization and chiroptical properties of these alternating copolymers steered by light and its state of polarization can be dynamically controlled. The configuration of the stereogenic centers in the side chains of the fluorene units determines the handedness of the cholesteric organization in thermally annealed films, indicating cooperative behavior. The polymer alignment and helicity of the supramolecular arrangement can be switched by irradiating with linearly and circularly polarized light, respectively. Intriguingly, when switching the handedness of thermally induced cholesteric organizations by illuminating with circularly polarized light that is opposite to the handedness of the cholesteric phases, a nematic‐like intermediate state is observed during helix interconversion. By the sequence of irradiation with left and right circularly polarized light followed by thermal annealing, an asymmetric motion, reminiscent of that seen in molecular motors is observed. These findings suggest that functional conjugated polymers can exhibit emergent properties at mesoscopic scale.

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“…The ability to understand and control the nanoscale organization of soft matter has become increasingly important for the development of advanced materials with tunable properties. − For example, the assembly of conjugated semiconducting polymers into ordered structures has a profound effect on their optoelectronic characteristics due to enhanced π–π stacking. − These noncovalent π–π interactions exist between the unhybridized p z orbitals of the aromatic rings and conjugated backbones in adjacent polymer chains, increasing the delocalization of electrons and allowing charge-carriers to move more easily . Therefore, the performance of devices using semiconducting polymers is strongly tied to the alignment of the polymer chains .…”

Section: Introductionmentioning

confidence: 99%

Enhanced Alignment of Water-Soluble Polythiophene Using Cellulose Nanocrystals as a Liquid Crystal Template

et al. 2017

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Cellulose nanocrystals (CNCs) are bioderived, rodlike particles that form a chiral nematic liquid crystal (LC) in water. In this work, CNCs were used to induce long-range order in a semiconducting polymer, poly[3-(potassium-4-butanoate) thiophene-2,5-diyl] (PPBT). When mixed with CNCs, it was found that PPBT was incorporated into the liquid crystal "template" to form ordered structures with highly birefringent domains, as observed under polarized light. We show that the π-π interactions between polymer chains, which contribute considerably to the energetics of the semiconducting system, are directly influenced by the presence and packing of the liquid crystal phase. Upon increasing the concentration of CNCs from the isotropic to chiral nematic regime, we observe a bathochromic shift in the UV-vis spectra and the emergence of the 0-0 vibrational peak, suggesting enhanced π-π stacking leading to chain coplanarization. Furthermore, the chiral nature of the PPBT/CNC mixture was evidenced by a negative peak in circular dichroism (CD) spectroscopy, promoting the notion that the polymer chains followed the helicoidal twist of the chiral nematic liquid crystal host. At high temperatures, the peak height ratios and overall intensities of the UV-vis and CD spectra associated with PPBT decreased as the chiral nematic pitch grew larger in size.

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Supramolecular ordered photochromic cholesteric polymers as smart labels for thermal monitoring applications

Cited by 8 publications

References 37 publications

Chiroptical Properties in Thin Films of π-Conjugated Systems

Chiroptical Properties in Thin Films of π-Conjugated Systems

Consequences of Chirality in Directing the Pathway of Cholesteric Helix Inversion of π‐Conjugated Polymers by Light

Enhanced Alignment of Water-Soluble Polythiophene Using Cellulose Nanocrystals as a Liquid Crystal Template

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