Fluorescence investigation of model compounds for light-emitting alternating copolymers in heterogeneous environments.
In this paper, the fluorescence spectra of the model compounds M(TPA-PPV) and M(TPA-PAV) of novel light-emitting alternating copolymers, were studied and the effect of KNO3 on the interaction between the model compounds and the ionic micelle-water interface was also investigated. The following is found: (i) the fluorescence changes of M(TPA-PPV) are related to the state of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) solution: (ii) an aggregated state can be formed in M(TPA-PAV) solution at low concentration of CTAB; (iii) higher concentrations of KNO3 may affect the interaction between the model compounds and the ionic micelle-water interface.
The effect of micelle-water interface electric field on the intramolecular charge transfer within ionic micelle - Dual fluorescence of sodium p-dialkylaminobenzoates in cetyltrimethylammonium micelles
Abstract Photoinduced intramolecular charge transfer (CT) of sodium p-(dimethylamino)- and p-(diethylamino) benzoates (SDMAB and SDEAB) in cetyltrimethylammonium bromide and chloride (CTAB and CTAC) micellar solutions was investigated by the CT typical dual fluorescence, in order to identify the effect of micelle–water interface electric field on the CT process occurring within ionic micelle. The CT fluorescence in CTAB and CTAC micelles was blue shifted and enhanced compared to those in pure water. The intensity ratio of the CT fluorescence to the LE fluorescence, Ia/Ib, of either SDMAB or SDEAB was found to be higher in CTAC micelle than in CTAB micelle, while these fluorophores experience the same polarity in both micelle environments. It was proposed that the higher Ia/Ib ratio in CTAC micelle was due to stronger electric field at CTAC micelle–water interface. This was supported by experiments on the dual fluorescence of SDEAB and SDMAB of different CT-state dipole moment in CTAB micelles of varying micelle–water interface electric field. It was demonstrated that the electric field at the ionic micelle–water interface indeed affected the CT process occurring within micelle that the CT process is promoted and the CT emission is enhanced at higher electric field. Ionic micelle was shown capable of acting as the electric field ‘mediator’ for chemo- and biosensing based on the dependence of the CT dual fluorescence on electric field.
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.