Molecular-scale asymmetry and memory behavior in poly(vinyl acetate) monitored with mobility-sensitive fluorescent molecules

Royal, J. Scot; Torkelson, John M.

doi:10.1021/ma00032a013

Cited by 46 publications

(37 citation statements)

References 10 publications

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“…Third, using dye labels other than pyrene, our group has developed intensity-related fluorescence methods to investigate physical aging rates in polymer films, 9,84,85 including the distribution of physical aging rates in substrate-supported polymer films.…”

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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

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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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mentioning

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

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110

106

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“…This is because photon emission increases when non-radiative processes are hindered by lack of mobility of the probe. Interestingly, studies on poly (vinyl acetate) (PVAc) have shown that changes in the fluorescence intensities with aging time and temperature follow closely those observed by volumetric relaxation [85].…”

Section: Other Spectroscopic Techniquesmentioning

confidence: 72%

“…In addition to PALS, other spectroscopic techniques that have been used to inves tigate physical aging are electron spin resonance spectroscopy (ESR) [83], fluores cence spectroscopy [84][85][86], dielectric spectroscopy [87], and Fourier-transform infrared spectroscopy (FTIR) [88].…”

Section: Other Spectroscopic Techniquesmentioning

confidence: 99%

Physical Aging of Polymer Blends

Cowie

Arrighi

2010

Encyclopedia of Polymer Blends

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Introduction to Physical AgingWhen a polymeric material is processed, fabricated, and placed in its working environment it cannot be regarded, automatically, as being stable, as it is subject to a wide range of possible changes, collectively known as aging processes. The polymer can react with its environment (light, oxygen, water, etc.) and undergo several non-reversible chemical reactions. These lead to changes in the polymer structure such as chain scission, oxidation, decarboxylation, hydrolysis, dehalogena tion, crosslinking, and so on, leading to degeneration of the polymer physical properties, for example, discoloration, brittleness, or loss of tensile strength. This type of aging will not be considered here.More subtle changes can also take place that do not involve chemical modification. These are a consequence of small-scale relaxation events that take place predomi nantly in the amorphous regions of glassy polymers, at temperatures below the glass transition temperature, g . The resulting effects are referred to as physical aging and, unlike chemical aging, are reversible.In physical aging the chemical structure of the polymer chain remains unchanged but the local packing of the chains alters over a period of time, leading to changes in the bulk properties of the material [1].When an amorphous, or semi-amorphous, polymer is quenched from the melt to a temperature a , below g , there is insufficient time for the chains to relax fully to their lowest energy configurations and a vitreous state is formed that is not in equilibrium with its surroundings. Such a state will have an excess enthalpy, entropy, and volume, and if the material is held at that temperature it will attempt to move towards a state of thermodynamic equilibrium by losing those excess quantities over a period of time. This is achieved through a series of localized molecular relaxation processes that is termed physical aging and is manifest as the time dependent alteration in polymer properties (density, modulus, compliance, g , material dimensions, and fracture toughness) at zero stress and constant temperature. Clearly, such changes will have an impact on the use and long-term stability of materials like high-performance thermoplastics and composites that are manufactured using techniques involving Edited by Avraam I. Isayev

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“…1 shows the change in fluorescence emission characteristics for a trace level of TC1 freely doped into PVAc film upon going from a dry state to equilibrium sorption of water (, 4.5 wt%) at room temperature. The most striking feature is the greater than 50% reduction in fluorescence intensity due to the uptake of , 4.5 wt% water (based on dry polymer), associated with plasticization effect of water on PVAc leading to both an increase in bulk matrix mobility, as evidenced by a reduction in glass transition temperature [26], and an increase in local mobility sensed by the TC1 probes. Also apparent upon close inspection of Fig.…”

Section: Resultsmentioning

confidence: 99%

In situ monitoring of sorption and drying of polymer films and coatings: self-referencing, nearly temperature-independent fluorescence sensors

Ellison

Miller

Torkelson

2004

Polymer

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Molecular-scale asymmetry and memory behavior in poly(vinyl acetate) monitored with mobility-sensitive fluorescent molecules

Cited by 46 publications

References 10 publications

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

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

Physical Aging of Polymer Blends

In situ monitoring of sorption and drying of polymer films and coatings: self-referencing, nearly temperature-independent fluorescence sensors

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