Interactions between hydrophobically modified alkali-swellable emulsion polymers and sodium dodecyl sulfate probed by fluorescence and rheology.

The interactions between a pyrene-labeled hydrophobically modified alkali-swellable emulsion (Py-HASE) polymer and the anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution were investigated with a fluorometer, a rheometer, and a combination of both instruments to probe the fluorescence of the polymer while the solution was being sheared. Different amounts of SDS were added to two solutions with Py-HASE concentrations of 8 and 57 g/L. The pyrene monomer and excimer decays of the Py-HASE solutions were acquired and globally fitted according to the fluorescence blob model (FBM) and the model free (MF) analysis.

Molar absorbance coefficient of pyrene aggregates in water generated by a poly(ethylene oxide) capped at a single end with pyrene.

The molar absorbance coefficient of ground-state pyrene aggregates (ε(E0)(λ)) in water generated by a short poly(ethylene oxide) chain labeled at a single end with a 1-pyrenemethoxide unit, namely, the polymeric construct Py₁-PEO(2.5K), was determined by a combination of UV-vis absorption and time-resolved fluorescence experiments. Since direct excitation of ground-state pyrene aggregates results in instantaneous excimer emission, whereas excimer formation by diffusive encounters between an excited- and a ground-state pyrene is delayed, acquisition of a pyrene monomer and excimer fluorescence decays with 1 nm increments of the excitation wavelength can probe the subtle effect that the excitation wavelength has on the extent of instantaneous excimer formation.

Nanodomain formation in lipid membranes probed by time-resolved fluorescence.

Time-resolved fluorescence measurements on liposomes prepared with 1 mol % pyrene-labeled lipids (PLLs) with a headgroup bearing either an alcohol (PSOH) or an imido diacetic acid (PSIDA) and 99 mol % 1-palmitoyl-2-oleyl-3-sn-phosphatidylcholines (POPC) or 99 mol % distearylphosphatidylcholine (DSPC) were performed to investigate how lipids phase separate within the membrane bilayer. Global analysis of the fluorescence decays with the fluorescence blob model (FBM) led to the conclusion that the PLLs were homogeneously distributed on the surface of POPC vesicles while the PLLs phase-separated in the DSPC vesicles. The analysis yielded the fraction of aggregated pyrenes, f(agg).

Molar absorption coefficient of pyrene aggregates in water.

The molar absorption coefficient of pyrene aggregates, epsilon(E0), was determined for a series of pyrene-labeled poly(N,N-dimethylacrylamide)s (Py-PDMA) having different pyrene contents. Aqueous solutions of Py-PDMA having pyrene contents ranging from 263 to 645 mumol of pyrene per gram of polymer were studied by UV-vis absorbance and time-resolved fluorescence spectroscopy. The global analysis of the monomer and excimer fluorescence decays with the fluorescence blob model yielded the fractions of the overall absorption contributed by all the pyrene species present in solution.

Comparison of the association level of a pyrene-labeled associative polymer obtained from an analysis based on two different models.

A hydrophobically modified alkali swellable emulsion copolymer (HASE) was labeled with pyrene and its fluorescence behavior was monitored by steady-state and time-resolved fluorescence as increasing amounts of the surfactant sodium dodecyl sulfate (SDS) were added to the solution. In aqueous solution, the pyrene pendants are aggregated. As SDS is added, the surfactant binds to the pyrene aggregates, which leads to their breakup at an onset SDS concentration of 1.