2 research outputs found
Autonomous Shuttling Driven by an Oscillating Reaction: Proof of Principle in a Cucurbit[7]uril-Bodipy Pseudorotaxane
A bipyridinium dication-substituted Bodipy fluorophore, with a terminal carboxylic acid function, provides two alternative stations for cucurbit[7]uril. Changing pH from basic to acidic results in shuttling of the cucurbit[7]uril from one station to another. In addition, this shuttling is accompanied by a change in the emissive properties of the Bodipy dye, which is only observed in the presence of cucurbit[7]uril. More striking, is a demonstration of autonomous shuttling of the pseudorotaxane system in an oscillating pH system
La naissance des jeux olympiques et le sport dans l'antiquité
The
ultrasound-induced cleavage of macromolecules has become a routine
experiment in the emerging field of polymer mechanochemistry. To date,
it has not been conclusively proven whether the molecular weight of
a polymer or its contour length is the determining factor for chain
scission upon ultrasonication. Here we report comparative experiments
that confirm unequivocally that the contour length is the decisive
parameter. We utilized postpolymerization modifications of specifically
designed precursor polymers to create polymers with identical chain
length but different molecular mass. To demonstrate the universality
of the findings, two different polymer backbones were utilizedî—¸polyÂ(styrene)
and polyÂ(norbornene imide alkyne)î—¸whose molecular weights were
altered by bromination and removal of pendant triisopropylsilyl protecting
groups, respectively. Solutions of the respective polymer pairs were
subjected to pulsed ultrasound at 20 kHz and 10.4 W/cm<sup>2</sup> in order to investigate the chain scission trends. The effects of
cleavage and sonochemical treatments were monitored by size exclusion
chromatography. In both series, experimental data and calculations
show that the molecular weight reduction upon sonication is the same
for polymers with the same contour length