Long Range Polymer Chain Dynamics Studied by Fluorescence Quenching

Farhangi, Shiva; Duhamel, Jean

doi:10.1021/acs.macromol.6b01295

Cited by 28 publications

(93 citation statements)

References 77 publications

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“…16 In polymers such as MEH-PPV, this phenomenon is expected to occur, since it presents several emitting moieties over which the exciton is delocalized 17 to achieve local excitation energy minima. 53 MEH-PPV samples in this work contain several emitting moieties that present their own absorption and fluorescence spectra. There, blue-region fluorescent collapsed H-aggregates are excited by higher energy wavelengths and are believed to have a small contribution to the overall fluorescence of MEH-PPV usual systems.…”

Section: Fluorescence Of Thin Films and Blendsmentioning

confidence: 99%

“…Huser et al 50 studied the several types of aggregates in films cast from solutions of distinct solvents, which are the reason for the multicolored fluorescence they observed. Also, Duhamel et al [51][52][53][54] demonstrated that intermolecular interactions can be quantitatively described by steady-state and time-resolved fluorescence spectroscopy, since the distinct aggregates present distinct photophysics. Vol.…”

mentioning

confidence: 99%

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Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Ribeiro¹,

Camargo²,

Pereira³

et al. 2017

J. Braz. Chem. Soc.

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In this work, we examined how photoluminescence in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is affected by morphology, dictated by the mode of preparation. For that, MEH-PPV dilute solutions in good and non-solvents, thick cast films with poly[methylmethacrylate] (PMMA) as inert matrix and spin-coated thin films were prepared. These systems were studied by steady-state and time-dependent fluorescence spectroscopy and electronic microscopy. Unexpected photoluminescent behavior was detected in solutions and films and it was related to different excitons modulated by MEH-PPV conformation. By semi empirical calculations we obtained the singlet and triplet state energies of an MEH-PPV model system and, from time-resolved fluorescence spectroscopy, the existence of short-lived excited states was revealed, enabling us to infer on possible singlet fission in MEH-PPV-based systems.Keywords: photoluminescence, morphology, thin films, time-resolved fluorescence, computational calculations IntroductionSince poly(phenylene-vinylene) (PPV) derivatives were found to be electroluminescent, 1 the search for a systematic method to determine their applications has been of great interest. Their mechanical, morphological and optical properties have been widely discussed and findings related these properties to preparation methods. Although there are many aspects regarding the effects of preparation methods on optical response, authors seem to agree that preparation method influences molecular conformation, enabling or inhibiting aggregation and, consequently, affecting inter and intrachain interactions. Processing parameters are believed to modify the conformation and assembling mechanisms of polymeric materials, resulting in a memory effect of the structural information that is replicated from solutions to solid films. Therefore, to understand the role of chain conformation in solution is of major importance for applications such as device fabrication, since properties can be tuned, enhancing the desired characteristics and suppressing the undesired ones. 2,3 For instance, it is well known that photoluminescence of PPV derivatives show prominent red-shift due to the enhancement of energy transfer as the π-electron delocalization increases. 4 As pointed out in an earlier work, 5 this red-shift indicates aggregation driven by π-π interactions as the conjugation length increases.In polymeric systems, several occurrences are responsible for chain torsions that impose limits to the length of conjugated segments, affecting the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps. They are interpreted as stabilization and/or destabilization of HOMO and LUMO levels. 6 These occurrences may be related to the presence of impurities, molecules of solvent that strongly interact with the polymer chains and a distribution of torsion angles promoted by molecular interactions of any nature. 6 In this situation, the densities of excited states (DOS) available for electronic chan...

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Section: Fluorescence Of Thin Films and Blendsmentioning

confidence: 99%

mentioning

confidence: 99%

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Ribeiro¹,

Camargo²,

Pereira³

et al. 2017

J. Braz. Chem. Soc.

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“…Furthermore, fluorescence techniques can isolate the signal of a fluorescently labeled macromolecule from that of a complex mixture of chemicals that do not fluoresce, or whose fluorescence can be accounted for independently. The past 35 years have witnessed tremendous developments in the characterization of macromolecules based on pyrene excimer fluorescence or PEF and many of these developments have been summarized . However, the experiments conducted to demonstrate their applicability to the characterization of maleated polyisobutylene (PIB) or ethylene‐propylene (EP) copolymers, which are building blocks used to prepare dispersants for engine oils, have not been reviewed so far.…”

Section: Characterization Of Polymeric Oil Additivesmentioning

confidence: 99%

“…At such a low pyrene content, pyrene is a true reporter of the behavior of the polymer and does not affect its behavior in organic solvents. Finally, pyrene excimer formation between two pyrene labels attached randomly onto a linear chain is a local phenomenon that occurs over a few tens of structural units within a volume referred to as a blob . Consequently, pyrene excimer formation might become affected by polymer entanglements only in the concentrated regime at polymer concentrations of several 100s of g L −1 when the length scale of a blob becomes comparable to that between entanglements …”

Section: Pyrene Excimer Fluorescence (Pef)mentioning

confidence: 99%

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New approaches to characterize polymeric oil additives in solution based on pyrene excimer fluorescence

Pirouz¹,

Duhamel²

2016

J. Polym. Sci. Part B: Polym. Phys.

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Maleated polyolefins (MaPOs) such as maleated ethylene propylene copolymers or polyisobutylene terminated at one end with a succininic anhydride can be used as polymeric dispersants in engine oils after reaction with polyamines while unmodified EP copolymers improve the viscosity index of oils. MaPOs can also be labeled with pyrene derivatives to generate pyrene-labeled polyolefins (PyLPOs) as fluorescent mimics of oil additives and pyrene excimer fluorescence (PEF) can be applied to probe their behavior in solution. This review describes new methodology that was recently implemented to characterize the complex fluorescence signal emitted by PyLPOs by using steady-state and time-resolved fluorescence. This methodology enables one to gain quantitative information about the level of clustering of the succinic pendants along a maleated polyolefins and intra-and intermolecular aggregation of polyolefins in solution. Such information is relevant to scientists aiming to characterize polymeric oil additives used in engine oil.

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Does Selectivity of Molecular Catalysts Change with Time? Polymerization Imaged by Single‐Molecule Spectroscopy

et al. 2020

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The chemoselectivity of molecular catalysts underpins much of modern synthetic organic chemistry. However, little is known about the selectivity of individual catalysts because this single-catalyst-level behavior is hidden by the bulk catalytic behavior. Here, for the first time, the selectivity of individual molecular catalysts for two different reactions is imaged in real time at the single-catalyst level. This imaging is achieved through fluorescence microscopy paired with spectral probes that produce a snapshot of the instantaneous chemoselectivity of a single catalyst for either a single-chainelongation or a single-chain-termination event during ruthenium-catalyzed polymerization. Superresolution imaging of multiple selectivity events, each at a different single-molecular ruthenium catalyst, indicates that catalyst selectivity may be unexpectedly spatially and time-variable.

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Long Range Polymer Chain Dynamics Studied by Fluorescence Quenching

Abstract: ABSTRACT

Cited by 28 publications

References 77 publications

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

New approaches to characterize polymeric oil additives in solution based on pyrene excimer fluorescence

Does Selectivity of Molecular Catalysts Change with Time? Polymerization Imaged by Single‐Molecule Spectroscopy

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