Fluorescence probes for investigation of epoxy systems and monitoring of crosslinking processes

Strehmel, Bernd; Strehmel, Veronika; Younes, M.

doi:10.1002/(sici)1099-0488(19990701)37:13<1367::aid-polb3>3.0.co;2-k

Cited by 55 publications

(12 citation statements)

References 69 publications

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“…Application of the Gierer-Wirtz theory gives information about the influence of microviscosity on the entire dynamic processes of a probe molecule in a matrix. [46][47][48] The plot of h/t as a function of h x according to the theory of Gierer and Wirtz results in a linear function as described by Eqn (2). The exponent x is an expression for the function of the activation energy for the viscous flow (E h ) and the activation energy for the jump into the free volume (E 2 ) as shown in Eqn (3).…”

Section: Resultsmentioning

confidence: 99%

Mobility of spin probes in ionic liquids

Strehmel

Laschewsky

Stoêsser

et al. 2006

J of Physical Organic Chem

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The spin probes TEMPO, TEMPOL, and CAT-1 were used to investigate microviscosity and micropolarity of imidazolium based ionic liquids bearing either tetrafluoroborate or hexafluorophosphate as anions and a variation of the substitution at the imidazolium ion. The average rotational correlation times (r) obtained by complete simulation of the X-band ESR spectra of TEMPO, TEMPOL, and CAT-1 increase with increasing viscosity of the ionic liquid although no Stokes Einstein behavior is observed. This is caused by microviscosity effects of the ionic liquids shown by application of the Gierer-Wirtz theory. Interestingly, the jump of the probe molecule into the free volume of the ionic liquids is a nonactivated process. The hyperfine coupling constants (A(iso) (N-14)) of TEMPO and TEMPOL dissolved in the ionic liquids do not depend on the structure of the ionic liquids. The A(iso) (N-14) values show a micropolarity of the ionic liquids that is comparable with methylenchloride in case of TEMPO and with dimethylsulfoxide in case of TEMPOL. Micropolarity monitored by CAT-1 strongly depends on structural variation of the ionic liquid. CAT-1 dissolved in imidazolium salts substituted with shorter alkyl chains at the nitrogen atom exhibits a micropolarity comparable with dimethylsulfoxide. A significant lower micropolarity is found for imidazolium. salts bearing a longer alkyl substituent at the nitrogen atom or a methyl substituent at C-2

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Section: Resultsmentioning

confidence: 99%

Mobility of spin probes in ionic liquids

Strehmel

Laschewsky

Stoêsser

et al. 2006

J of Physical Organic Chem

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“…Environment sensitive fluorescent probes have been widely used to study phase separation in polymer blends 27,28 , polymerization reactions and sol-gel transformations 29, 30 , pH monitoring of the biological cells 31 , water uptake in polymeric films 32,33 , for determining the polarity of micellar systems 34,35 and to determine the critical micelle concentration (CMC) of surfactants 36 . Recently, they have also been used to determine the "amorphous solubility" of pharmaceutical compounds 37,38 .…”

Section: Introductionmentioning

confidence: 99%

Phase Separation Kinetics in Amorphous Solid Dispersions Upon Exposure to Water

Purohit

Taylor

2015

Mol. Pharmaceutics

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The purpose of this study was to develop a novel fluorescence technique employing environment-sensitive fluorescent probes to study phase separation kinetics in hydrated matrices of amorphous solid dispersions (ASDs) following storage at high humidity and during dissolution. The initial miscibility of the ASDs was confirmed using infrared (IR) spectroscopy and differential scanning calorimetry (DSC). Fluorescence spectroscopy, as an independent primary technique, was used together with conventional confirmatory techniques including DSC, X-ray diffraction (XRD), fluorescence microscopy, and IR spectroscopy to study phase separation phenomena. By monitoring the emission characteristics of the environment-sensitive fluorescent probes, it was possible to successfully monitor amorphous-amorphous phase separation (AAPS) as a function of time in probucol-poly(vinylpyrrolidone) (PVP) and ritonavir-PVP ASDs after exposure to water. In contrast, a ritonavir-hydroxypropylmethylcellulose acetate succinate (HPMCAS) ASD, did not show AAPS and was used as a control to demonstrate the capability of the newly developed fluorescence method to differentiate systems that showed no phase separation following exposure to water versus those that did. The results from the fluorescence studies were in good agreement with results obtained using various other complementary techniques. Thus, fluorescence spectroscopy can be utilized as a fast and efficient tool to detect and monitor the kinetics of phase transformations in amorphous solid dispersions during hydration and will help provide mechanistic insight into the stability and dissolution behavior of amorphous solid dispersions.

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“…The restricted fluorophore mobility increases the emission intensity because the fluorophore can dissipate the excitation through non-radiative processes less effectively. While fluorescence has been used to study the curing characteristics of bulk epoxy resin and silanized glass/epoxy interfaces, [3,[16][17][18][19] confocal microscopy has not been used to map a temperature gradient cured epoxy library at or near the surface of the film.…”

Section: Introductionmentioning

confidence: 99%

Combinatorial Approach to Characterizing Epoxy Curing

Eidelman

Raghavan

Forster

et al. 2004

Macromol. Rapid Commun.

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Summary: Three complementary techniques that probe different characteristics of curing: FTIR microspectroscopy, confocal microscopy and axisymmetric adhesion testing were used to study discrete epoxy samples cured at different temperatures and to follow curing across a continuous gradient combinatorial library. Together, these techniques provide a comprehensive picture of chemical and physical changes.FTIR microspectroscopy map of epoxy film cured on a temperature gradient. Red represents the highest and blue the lowest curing.magnified imageFTIR microspectroscopy map of epoxy film cured on a temperature gradient. Red represents the highest and blue the lowest curing.

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Fluorescence probes for investigation of epoxy systems and monitoring of crosslinking processes

Cited by 55 publications

References 69 publications

Mobility of spin probes in ionic liquids

Mobility of spin probes in ionic liquids

Phase Separation Kinetics in Amorphous Solid Dispersions Upon Exposure to Water

Combinatorial Approach to Characterizing Epoxy Curing

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