Herman J. Verhey

Crosslinking and drying of a two-component waterborne coating monitored by a functionalized charge-transfer fluorescence probe

A donor-bridge-acceptor fluorophore with extreme sensitivity to environmental influences has been attached covalently to a polyamino crosslinker. It was found that the progress of the crosslinking reaction with an aceto-acetate functionalized polyacrylate dispersion can be monitored from the fluorescence wavelength shift of the fluorophore. Also formation and drying of films applied from the resulting labelled dispersion induces a significant wavelength shift of the fluorescence of the incorporated label.

Fluorescence lifetime studies of labelled polystyrene latices

Abstract A charge-transfer fluorescence molecule has been applied to study the structure of polystyrene latices and polystyrene—glycidylmethacrylate core—shell latices. Information on the composition of the latex could be obtained on the basis of the combined application of steady state and time-resolved fluorescence measurements. Time-resolved measurements were done using a frequency-domain approach; the time-resolved data were interpreted using the maximum entropy method of analysis.

Time-resolved spectroscopy of charge-transfer fluorescent molecules in polymer matrices

Time-resolved fluorescence measurements have been carried out on charge-transfer fluorescent molecules incorporated in polymeric lattices, consisting of polystyrene cores and polyglycidylmethacrylate shells, and in polymethylmethacrylate thin films. New approaches to the analysis of fluorescence lifetime data obtained for molecules in polymer matrices had to be applied, since conventional analysis methods appeared not suitable for such strongly heterogeneous systems. The polymer lattices could be characterized by application of phase- resolved fluorescence lifetime measurements followed by maximum-entropy methods for data analysis. The thin films were studied using time-correlated single photon counting fluorescence lifetime measurements and data analysis with a home-built program based on stretched exponential decays. Interactions of the fluorescent guest molecules could be established by combined fluorescence lifetime and depolarization measurements. Suggestions for further improvements in fluorescence lifetime methods for characterization of polymeric materials have been made.

Intramolecular charge-transfer fluorescence of 4-(4-cyano-1-naphthylmethylene)-1-phenylpiperidine in cyclohexane–methyl acetate binary mixtures and related aliphatic esters. Polarity vs. mobility control of the relaxation of a highly dipolar excited state

The charge transfer (CT) emissive behaviour of the dipolar excited state of 4-(4-cyano-1-naphthylmethylene)-1-phenylpiperidine and two of its derivatives, containing an alkyl chain at the para position of the dialkylanilino donor moiety is studied in cyclohexane–methyl acetate binary solvent mixtures and structurally related liquid and solid aliphatic esters. In the liquid matrices, changes of the CT emission maximum can be related to stabilization of the dipolar excited state by the polarity of the matrix sites, which accommodate the probe molecule. However, in solid matrices, the relaxation behaviour of the dipolar excited state is affected mainly by the mobility of the matrix sites.

Intramolecular Charge Transfer Fluorescence of 1-Phenyl-4-(4-Cyano-1-Naphthylmethylene)Piperidine as a Mobility Probe in α,ω-Diacetyl Poly(Ethyleneglycols)

Continuous- and time-resolved fluorescence measurements of l-phenyl-4-(4-cyano-l-naphthyl-methylene)piperidine (Fluoroprobe) dissolved in α,ω-diacetyl poly(ethyleneglycols) show that fluorescence occurs prior to full relaxation of the surrounding matrix sites.