Long-Range Polymer Chain Dynamics of Pyrene-Labeled Poly( N -isopropylacrylamide)s Studied by Fluorescence

2012

Polymers

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147

Abstract:This review exposes the current poor understanding of the internal segmental chain dynamics of dendrimers in solution probed by monitoring the process of excimer formation between pyrene labels covalently attached to the chain ends of dendrimers. The review begins by covering the bases of fluorescence and the kinetics of pyrene excimer formation before describing a procedure based on the Model Free (MF) analysis that is used to analyze quantitatively the fluorescence decays acquired for dendrimers, the ends of which have been fully and covalently labeled with pyrene. Comparison of the various trends obtained by different research groups describing the efficiency of pyrene excimer formation with the generation number of dendrimers illustrates the lack of consensus between the few studies devoted to the topic. One possible reason for this disagreement might reside in the presence of minute amounts of unattached pyrene labels which act as potent fluorescent impurities and affect the analysis of the fluorescence spectra and decays in an uncontrolled manner. The review points out that the MF analysis of the fluorescence decays acquired with pyrene-labeled dendrimers enables one to account for the presence of unattached pyrene and to retrieve information about the internal segmental dynamics of the dendrimer. It provides guidelines that should enable future studies on pyrene-labeled dendrimers to yield results that are more straightforward to interpret.

Section: Analysis Of the Kinetics Of Excimer Formation For Pyrene-labmentioning

confidence: 99%

Internal Dynamics of Dendritic Molecules Probed by Pyrene Excimer Formation

2012

Polymers

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147

“…To date, the FBM has been applied to the analysis of the monomer and excimer decays acquired with several polymers randomly labeled with pyrene. 35,37,67,68,[72][73][74][75] Table 2. Chemical structure of the polystyrenes and poly(N-isopropylacrylamide) randomly labeled with pyrene.…”

Section: B) A)mentioning

confidence: 99%

Long Range Polymer Chain Dynamics Studied by Fluorescence Quenching

Farhangi

2016

Macromolecules

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“…Within experimental error, the values of <Nblob> and <kblob  Nblob> Furthermore <kblob  Nblob> was found to increase with increasing   in Figure 4B as would be expected from a diffusion controlled process for pyrene excimer formation. Since <kblob  Nblob> has been shown to faithfully represent the internal dynamics of polymers in solution, 22,24,25 this result demonstrates that the PyMeEGOH derivative used to label PBMA yields the same dynamic information on a polymer in solution as PyButOH does as would be expected since the linker connecting the pyrene derivatives to the PBMA backbone is constituted of a same number of four atoms. The main difference between these two pyrene derivatives is the ability of PyMeEGOH to probe the polarity of its local environment with a sensitivity that is similar to that of molecular pyrene (see Figures 1A and 2), a feature of this dye whose importance is rooted in the fact that the paper introducing this effect for the first time has been cited more than 1800 times since 1977 according to scifinder!…”

Section: Resultsmentioning

confidence: 68%

“…22,24,25 As for Nblob, the products kblob×Nblob were insensitive to pyrene content as shown in Figure S6. They were averaged over all constructs for a given Py-PBMA series to yield <kblob×Nblob> which was plotted as a function of   in Figure 4B.…”

Section: Resultsmentioning

confidence: 82%

See 1 more Smart Citation

Pyrenyl Derivative with a Four-Atom Linker That Can Probe the Local Polarity of Pyrene-Labeled Macromolecules

Farhangi

2016

J. Phys. Chem. B

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The fluorescent probe 1-pyrenemethoxyethanol (PyMeEGOH) was designed to replace commercially available 1-pyrenebutanol (PyButOH) as an alternative fluorescent label to probe the internal dynamics and interior polarity of macromolecules by steady-state and time-resolved fluorescence. While excimer formation and sensitivity to solvent polarity are two well-recognized properties of pyrene, much less known is that these properties are often mutually exclusive when a 1-pyrenebutyl derivative is used to prepare pyrene-labeled macromolecules (PyLMs). As the sensitivity of pyrene to solvent polarity is a result of its symmetry, attaching a butyl group to pyrene breaks the symmetry of pyrene, so that the 1-pyrenebutyl derivatives are much less sensitive to the polarity of their environment compared to unmodified pyrene. This report demonstrates that replacement of a methylene group in the β-position of PyButOH by an oxygen atom, such as in PyMeEGOH, restores the sensitivity of this pyrene derivative to the polarity of its local environment to the same level as that of molecular pyrene without impeding pyrene excimer formation upon incorporation into PyLMs.