Photo-response assisted enantiomer separations on an azobenzene-modified gamma-cyclodextrin stationary phase in micro-HPLC.
The photo-responses of the retention and enantioseparation of several optical isomers were evaluated using an azobenzene-modified gamma-cyclodextrin stationary phase (Az gamma-CDSP) in micro-HPLC. UV light irradiation induced a decrease in the retention and the chiral selectivity for N-(3,5-dinitrobenzoyl)-1-phenylethylamine (DNBPEA) and N-(3,5-dinitrobenzoyl)-1-(1-naphtylethyl)amine (DNBNEA), while an increase was induced for dansylphenylalanine (DnsPhe) using a mixture of methanol and aqueous phosphate buffer as the mobile phase. No changes in the retention and the enantiomer separation of benzoin were observed with UV light irradiation. The retention behaviors were recovered by visible-light irradiation. It was speculated that the main factor of the change in the retention behavior was a change in the pi-pi interaction due to the azobenzene moiety of the stationary phase with photo-irradiation. Comparing the retention behavior before and after UV light irradiation, a suitable condition for obtaining a better resolution and enantiomer separation would be chosen using Az gamma-CDSP.
Macrocycles containing azo groups: recognition, assembly and application
Macrocyclic compounds play an important role in supramolecular chemistry accounting for their unique recognition and self-assembly properties and potential applications in biomedicine and material science. Azo compounds display promising capability in fields of molecular switches, polymers, smart materials and molecular machines because of their photoactive and electroactive properties. Introducing azo groups into macrocycles gives them signal moieties, additional recognition sites, photo-responsive properties, and so on. Herein, we comprehensively review the structures of azo-containing macrocyclic compounds reported up to now. Then we describe representative works on azo macrocycles with their molecular recognition, self-assembly and application emphasized.
Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes
Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F2) or atomic (Fradical dot) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F2 or a specific reagent XeF2, which releases atomic fluorine Fradical dot. Changes of LDPE chemical composition were investigated by FTIR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AFM). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of single bondCF2single bond, was formed during the direct fluorination conditions (F2). For the process performed with XeF2, specific groups single bondCHFsingle bond were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with Fradical dot (originated from XeF2 decomposition) resulted in single bondCHFsingle bond groups in bulk prevailing formation whereas F2 formed mainly single bondCF2single bond groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase.