Chiral Recognition of 18-Crown-6-tetracarboxylic Acid toward Amino Acids and Organic Amines by Fast Atom Bombardment Mass Spectrometry.A Comparison with Capillary Electrophoresis

Chiral recognition of the host-guest complexations between the (RRRR)-18-crown-6-tetracarboxylic acid (18 C6TCA) host (H) and α-amino acid or their ester derivative guests (G) has been systematically determined using both FAB mass spectrometry (MS) and capillary zone electrophoresis (CE). A comparison of these two techniques for the same series of guests was then done for the first lime. In the case of 18C6TCA，we found that there is no correlation between the chiral recognition obtained from FABMS (i.e.，the IRIS value)and from CE(i.e.，the α value in an aqueous buffer solution) covering three sets of guests including amino acids，amino acid esters，and primary aromatic amines. On the other hand. the former showed a good agreement with that from NMR (i.e.，the KR/Ks value: the ratio of the corresponding equilibrium constants)， supporting our earlier conclusion that FABMS is a good measurement tool for predicting differences (44G°values) in the respective chiral H-G interactions in solution. We also found that when a given guest changes from an amino acid to its corresponding amino acid　ester，the α value by CE dramatically changes from α>1.0 toα<1.0，though the IRIS value by FABMS does not show any such changes. These findings，were considered to be due to the characteristic contributions of the dissociable host\u27s COOH functions under the experimental pH conditions in CE

Preparation of Pickering emulsions through interfacial adsorption by soft cyclodextrin nanogels

Background: Emulsions stabilized by colloidal particles are known as Pickering emulsions. To date, soft microgel particles as well as inorganic and organic particles have been utilized as Pickering emulsifiers. Although cyclodextrin (CD) works as an attractive emulsion stabilizer through the formation of a CD–oil complex at the oil–water interface, a high concentration of CD is normally required. Our research focuses on an effective Pickering emulsifier based on a soft colloidal CD polymer (CD nanogel) with a unique surface-active property.Results: CD nanogels were prepared by crosslinking heptakis(2,6-di-O-methyl)-β-cyclodextrin with phenyl diisocyanate and subsequent immersion of the resulting polymer in water. A dynamic light scattering study shows that primary CD nanogels with 30–50 nm diameter assemble into larger CD nanogels with 120 nm diameter by an increase in the concentration of CD nanogel from 0.01 to 0.1 wt %. The CD nanogel has a surface-active property at the air–water interface, which reduces the surface tension of water. The CD nanogel works as an effective Pickering emulsion stabilizer even at a low concentration (0.1 wt %), forming stable oil-in-water emulsions through interfacial adsorption by the CD nanogels.Conclusion: Soft CD nanogel particles adsorb at the oil–water interface with an effective coverage by forming a strong interconnected network and form a stable Pickering emulsion. The adsorption property of CD nanogels on the droplet surface has great potential to become new microcapsule building blocks with porous surfaces. These microcapsules may act as stimuli-responsive nanocarriers and nanocontainers

Release Behavior of Benzimidazole-Intercalated α-Zirconium Phosphate as a Latent Thermal Initiator in the Reaction of Epoxy Resin

The intercalation compound of benzimidazole with &alpha;-zirconium phosphate (&alpha;-ZrP) was evaluated as a latent thermal initiator in the reaction of glycidyl phenyl ether (GPE) and hexahydro-4-methylphthalic anhydride (MHHPA). No reaction occurred at 60 &deg;C after 1 h. Upon increasing the temperature to 140 &deg;C, the conversion reached 97% after 1 h. The deintercalation ratio of Bim from the intercalation compound of benzimidazole with &alpha;-zirconium phosphate (&alpha;-ZrP&middot;Bim) was measured in the reaction of the GPE-MHHPA system. The deintercalation ratio increased upon increasing the temperature, reaching 97% at 120 &deg;C after 1 h. The storage stability at 25 &deg;C and 40 &deg;C in the reaction of GPE-MHHPA was tested and was found to be maintained for 14 days at 25 &deg;C. The intercalation compound of &alpha;-ZrP&middot;Bim can effectively serve as a latent thermal initiator in the reaction of GPE-MHHPA