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Sieger durch Aggregatbildung: Der Einbau einer anionenbindenden Squaramidgruppe in ein Polymer bewirkt eine drastische Änderung der Selektivität und Stärke des anioneninduzierten Ansprechens, sodass man einen empfindlichen und selektiven Fluoreszenzsensor für Dihydrogenphosphat erhält. Das ungewöhnliche Verhalten des Sensors ist das Ergebnis eines kooperativen, anionengesteuerten Aggregationsprozesses (siehe Bild; Skalierung 1 μm).

A series of supported silver salts of heteropolyacid AgxH3-xPW/SiO2 (x=0.5, 1.0, 1.5, 2.0, 2.5, 3.0) were synthesized and showed high reactivity and stability in tetrahydrofuran polymerization, which were due to the saltsʹ insolubility in polar solvent. The amount of Ag ion replaced in the salt and the amount of the salt loaded on the silica significantly influenced the catalytic performance. Change in the Ag content of the supported silver salt altered the crystal phase composition of the silver tungstophoric acid and catalystʹs acid strength. The AgxH3-xPW/SiO2 catalyst had the highest acid strength and the highest polymerization activity when x=2.0. When the Ag2HPW loading was 30% (mass fraction), the catalyst exhibited the best dispersion and highest activity for the polymerization of tetrahydrofuran. Compared with the conventional silica supported heteropolyacid (HPW/SiO2) catalyst, the present 30%Ag2HPW/SiO2 displayed excellent reusability, with its reactivity only slightly declining after 4 reuses. Through the introduction of the Ag ion, the stability of the novel supported 30%Ag2HPW/SiO2 was significantly improved and the obtained polymer product, polytetrahydrofuran, had a stable average molecular weight.

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