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Solvation and Solvent Relaxation in Swellable Copolymers as Studied by Time-Resolved Fluorescence Spectroscopy (2000)

Egelhaaf, H.-J. ; Lehr, B. ; Hof, M. ; [et al.]

Springer

Journal of fluorescence 10 (2000), S. 383-392

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ISSN: 1573-4994

Keywords: DANSyl-labeled copolymers ; swelling volume ; time-resolved fluorescence ; solvent relaxation ; rotational depolarization

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract The fluorescent probe dimethylaminonaphthylsulfonamide is covalently bound to the ends of the pol(ethylene glycol) chains of the swellable block copolymers poly(ethylene glycol)–polystyrene (PEG-PS) and poly(ethylene glycol)–poly(ethylene imine) (PEG-PEI) to investigate the molecular mobility inside the polymers, swollen by different liquids. Steady-state and time-resolved studies of the Stokes shift between absorption and fluorescence spectra reveal that the probe is solvated by both the polymer matrix and the liquid phase. The extent of solvation by the liquid and the mobility of the microenvironment of the probe depend on both the swelling volume of the polymer and the solubility of the probe in this liquid. Steady-state and time-resolved fluorescence depolarisation measurements show that the polymer matrix forms a very rigid solvent cage, which almost completely immobilizes the probe. Upon solvation of the probe by the liquid, the mobility of the probe increases. In PEG-PEI swollen by polar solvents, the mobilities of the probe itself and of its microenvironment, although not reaching the values observed in homogeneous solution, are significantly higher than in PEG-PS, due to the hydrophilic nature of the polymeric backbone in PEG-PEI.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009482514437

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Über geordnete Perowskite mit Kationenfehlstellen. XI. Das System Ba2Gd2/3□1/3U1-xWxO6 (1982)

Wischert, W. ; Oelkrug, D. ; Schittenhelm, H.-J. ; [et al.]

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 495 (1982), S. 219-231

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ISSN: 0044-2313

Keywords: Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: On Ordered Perovskites with Cationic Vacancies. XI. System Ba2Gd2/3□1/3U1-xWxO6The cation deficient polymorphic perovskites Ba2Gd2/3□1/3UO6 and Ba2Gd2/3□1/3WO6 form a continuous series of mixed crystals, which crystallize over a wide range (x = 0.1 up to 0.99) in a cubic 1:1 ordered perovskite lattice. According to the investigations of the vibrational spectra, the diffuse reflectance spectra, and the photoluminescence - opposite to isostructural perovskites without vacancies - different species of UO6 and WO6 octahedra are present. Numerous differences in properties - e. g. an orange emission colour in comparison with a green one by absence of vacancies - are based upon that.

Notes: Die beiden fehlstellenhaltigen, polymorphen Perowskite Ba2Gd2/3□1/3UO6 und Ba2Gd2/3□1/3WO6 bilden eine lückenlose Reihe von Mischkristallen, die in einem weiten Bereich (x = 0,1 bis 0,99) in einem kubischen 1:1 geordneten Perowskitgitter kristallisieren. Wie die Untersuchung der Schwingungsspektren, der diffusen Reflexionsspektren und der Photolumineszenz zeigen, liegen - im Gegensatz zu isostrukturellen fehlstellenfreien Perowskiten - mehrere Sorten an UO6- und WO6-Oktaedern vor. Hierauf sind zahlreiche Eigenschaftsunterschiede - z. B. eine orangefarbene Emission im Unterschied zu einer grünen bei Abwesenheit von Fehlstellen - zurückzuführen.

Additional Material: 4 Ill.