RESUMEN
Pseudorotaxane complexes between ß-CD and mPEG derivatives bearing a carboxylic acid function (mPEG-COOH) were synthesized and investigated for their dispersing properties in a cement-based mortar. The formation of mPEG-COOH derivatives and their pseudorotaxanes was investigated by 1D nuclear magnetic resonance, diffusion ordered spectroscopy, and thermogravimetric analysis experiments. Mortar tests clearly indicate that mPEG-COOH@ß-CD-interpenetrated supramolecules show excellent dispersing abilities. In addition, the supramolecular complexes show a retarding effect, analogously to other known ß-CD-based superplasticizers in which the ß-CD is covalently grafted on a polymeric backbone.
RESUMEN
Water-soluble tetrasulfonate resorcin[4]arene (1a and 1c) and pyrogallol[4]arene (1b) macrocycles were synthesized and investigated for their dispersing properties in cement-based mortars. Mortar tests clearly show that these polyhydroxylated macrocycles (nonpolymeric) work as cement dispersants. Setting time determinations indicate that the macrocycles 1a and 1b show a retarding effect that is reminiscent of the behavior of superplasticizers (SPs) functionalized with polyhydroxylated ß-CDs. Finally, the addition of sulfate anions to the cement paste does not affect the dispersing abilities of 1b, probably due to the sulfate anion capture by H-bonding interactions with its OH groups at the upper rim.
RESUMEN
A preliminary assessment of properties of the commercial product Chemiplus 2DS HB (BI-QEM Specialties SpA) is proposed. Cyclic voltammetry of this oligomer containing sulfate/sulfone groups shows a single oxidative peak at +0.866 V vs. Ag/AgCl, and its passivating process on Pt electrode suggests the formation of a non-conductive layer. Electrode modification was achieved by exploiting the constant potential amperometry setting potential at +0.900 V vs. Ag/AgCl. A substantial change in the oxidative currents from electroactive species H2O2 and ascorbic acid (AA) were observed on Pt/Chemiplus 2DS HB sensors compared to unmodified Pt. Furthermore, the influence of different storage conditions on modified sensors was examined. A storage solution containing AA concentration from 0.1 until 10 mM maintained effective AA rejection of Pt/Chemiplus 2DS HB after 7 days from construction; H2O2 oxidation capability was also retained. Sulfone and sulfonate groups of Chemiplus 2DS HB are likely responsible for the dimensionality of the film and the electrostatic interaction leading to a self-blocking/self-rejection of AA. The way Pt/Chemiplus can reveal the AA presence depends on the maintaining of AA rejection, and this peculiarity can distinguish it from other sensors or biosensors.
