Static and Dynamic Fluorescence of Pyrene as Probes of Site Polarity and Morphology in Ethylene-<i>co</i>-(Vinyl Acetate) (Eva) Films

Prado, E.A; Yamaki, Sahori B.; Atvars, Teresa Dib Zambon; Zimerman, Oscar E.; Weiss, Richard G.

doi:10.1021/jp9931455

Cited by 53 publications

(62 citation statements)

References 51 publications

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“…In addition, lower τ in the surface than in bulk should also be expected taking into account that labels at the polymer-air surface may be quenched by oxygen more easily than in bulk. By the other hand, the same result than here reported, larger τ in the surface than in bulk, was observed for pyrene probes deposited on a polymer surface by sublimation of the chromophore 34 or in LB films in which pyrene probes motion was highly restricted so that τ were longer than those in THF solution. 35 This leaves an open question that will be studied in future work.…”

Section: Resultssupporting

confidence: 89%

Fluorescence Lifetime Distributions of Labeled Amorphous Polymers in Bulk

Serrano¹,

Baselga²,

Piérola³

2002

Polym J

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ABSTRACT:Polystyrene, poly(methylmethacrylate), poly(cyclohexyl methacrylate) and poly(1-butylmethacrylate) were labeled with anthryl groups by copolymerization. Films of labeled polymers as well as blends of them with unlabeled polystyrene samples of different polydispersity and molecular weight, were prepared by solvent casting. The time resolved emission of anthryl groups in those films was measured by Single Photon Counting with front face excitation at the standard 30• incident angle and with much lower incident angles to photoselect chromophores on the polymer-air surface. Fluorescence decays were fitted with bimodal fluorescence lifetime distributions, which were analyzed taking into consideration some polymer characteristics and the compatibility of polymer blends. It was thus concluded that solid-like and liquid-like environments are both in the bulk and in the surface of the film although liquid-like domains are more frequent on the surface than in bulk. Polymer T g determines the position of the two modes and polydispersity justify the broadness of the modes in the fluorescence lifetime distribution. KEY WORDS Fluorescence Lifetime Distribution / Fluorescence Decay / Poly(1-butylmethacrylate) / Poly(methylmethacrylate) / Poly(cyclohexylmethacrylate) / Polystyrene / Steady state or time-resolved fluorescence measurements of chromophores added to polymers as probes or labels can yield valuable information on the structural or dynamic properties of the system. 1 Anthryl groups have been broadly employed as polymer labels due to its well known photophysical behavior as well as to its relatively small size and high fluorescence quantum yield. 2, 3 Nevertheless, it was found 4 that the chain mobility of polystyrene (PS) is slightly reduced by the steric hindrance of the anthryl group with phenyl rings and therefore, minimum proportions of labeling groups must be introduced in the polymer to preserve unmodified the macroscopic polymer characteristics. Fortunately, due to the very high sensitivity of this technique, only very low chromophore concentrations are needed, which does not disturb the system properties. But even such low concentrations still report on its environment and on processes occurring in the nanosecond time range.It was shown 2 for anthracene dissolved in PS that rigidity and dimension of the matrix free volume are related with the vibronic structure of the fluorescence spectrum. The non-radiative deactivation processes, which involve out of plane vibrational modes and intermolecular interactions, are inhibited in polymer matrices. 2 As a consequence of the probe-polymer matrix interaction the fluorescence intensity changes with temperature following and revealing polymer relaxation processes. 5 Matrix effects on the radiationless deactivation of substituted anthracenes were also observed in films of poly(methylmethacrylate) (PMMA) and they were attributed to competing intersystem crossing and very fast internal conversion. 6 For 9-methylanthracene, 7 the radiationless deactivation rate coe...

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Section: Resultssupporting

confidence: 89%

Fluorescence Lifetime Distributions of Labeled Amorphous Polymers in Bulk

Serrano¹,

Baselga²,

Piérola³

2002

Polym J

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“…75,76 In the current study, we show that T g values can be obtained in supported polymer films and, for the first time, in free-standing polymer films using a self-referencing fluorescence intensity ratio. Additionally, we provide the first demonstration of the applicability of this approach for determination of T g as a function of confinement in free-standing PS films and show that our data are in approximate agreement with data obtained by Forrest and coworkers.…”

mentioning

confidence: 58%

“…The MApyrene-labeled PiBMA film provides the clearest indication of four peaks in the 370-415 nm wavelength range, which are characteristic of the fluorescence from the excited-state of a single pyrene molecule or pyrenyl chromophore. [75][76][77][80][81][82] In contrast to the fluorescence from the PiBMA film, the second fluorescence peak is virtually absent in the PS films.…”

Section: Fluorescence Measurementsmentioning

confidence: 99%

Effect of nanoscale confinement on the glass transition temperature of free‐standing polymer films: Novel, self‐referencing fluorescence method

Kim

Roth

Torkelson

2008

J Polym Sci B Polym Phys

110

106

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The effect of nanoscale confinement on the glass transition temperature, T g , of freely standing polystyrene (PS) films was determined using the temperature dependence of a fluorescence intensity ratio associated with pyrene dye labeled to the polymer. The ratio of the intensity of the third fluorescence peak to that of the first fluorescence peak in 1-pyrenylmethyl methacrylate-labeled PS (MApyrene-labeled PS) decreased with decreasing temperature, and the intersection of the linear temperature dependences in the rubbery and glassy states yielded the measurement of T g . The sensitivity of this method to T g was also shown in bulk, supported PS and poly(isobutyl methacrylate) films. With free-standing PS films, a strong effect of confinement on T g was evident at thicknesses less than 80-90 nm. For MApyrene-labeled PS with M n ¼ 701 kg mol À1 , a 41-nm-thick film exhibited a 47 K reduction in T g relative to bulk PS. A strong molecular weight dependence of the T g -confinement effect was also observed, with a 65-nm-thick free-standing film exhibiting a reduction in T g relative to bulk PS of 19 K with M n ¼ 701 kg mol À1 and 31 K with M n ¼ 1460 kg mol À1 . The data are in reasonable agreement with results of Forrest, DalnokiVeress, and Dutcher who performed the seminal studies on T g -confinement effects in free-standing PS films. The utility of self-referencing fluorescence for novel studies of confinement effects in free-standing films is discussed.

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“…Thus it appears that temperature changes in rigid polymer media affects more strongly the I 1 (S 1 ν=0 → S 0 ν=0 ) vibronic band transition than the I 3 (S 1 ν=0 → S 0 ν=1 ) band and this is probably due to differences in vibronic coupling contributions [23]. Analysis of the excitation spectra monitored at the emission of the first vibronic band of pyrene doped polymer films recorded at various temperatures, indicated that there was no excimer formation associated with these mild experimental conditions [32][33][34][35][36][37][38]. Figure 4d shows a plot of the thermally induced changes in the I 1 /I 3 ratio (py parameter) for the different dry poly(NIPAM-co-NtBA) films.…”

Section: Pyrene Fluorescencementioning

confidence: 99%

Polarity Assessment of Thermoresponsive Poly(NIPAM-co-NtBA) Copolymer Films Using Fluorescence Methods

et al. 2010

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The in-situ, non-contact, and non-destructive measurement of the physicochemical properties such as the polarity of thin (nm to µm), hydrophilic polymer films is desirable in many areas of polymer science. Polarity is a complex factor and encompasses a range of noncovalent interactions including dipolarity/polarizability and hydrogen bonding. A polarity measurement method based on fluorescence would be ideal, but the key challenge is to identify suitable probes which can accurately measure specific polarity related parameters. In this manuscript we assess a variety of fluorophores for measuring the polarity of a series of relatively hydrophilic, thermoresponsive N-isopropylacrylamide/N-tert-butylacrylamide (NIPAM/NtBA) copolymers. The emission properties of both pyrene and 3-Hydroxyflavone (3-HF) based fluorophores were measured in dry polymer films. In the case of pyrene, a relatively weak, linear relationship between polymer composition and the ratio of the first to the third vibronic band of the emission spectrum (I 1 /I 3 ) is observed, but pyrene emission is very sensitive to temperature and thus not suitable for robust polarity measurements. The 3-

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Static and Dynamic Fluorescence of Pyrene as Probes of Site Polarity and Morphology in Ethylene-co-(Vinyl Acetate) (Eva) Films

Cited by 53 publications

References 51 publications

Fluorescence Lifetime Distributions of Labeled Amorphous Polymers in Bulk

Fluorescence Lifetime Distributions of Labeled Amorphous Polymers in Bulk

Effect of nanoscale confinement on the glass transition temperature of free‐standing polymer films: Novel, self‐referencing fluorescence method

Polarity Assessment of Thermoresponsive Poly(NIPAM-co-NtBA) Copolymer Films Using Fluorescence Methods

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