Elucidation of multiple-point interactions of pyranine fluoroprobe during the gelation

Phase Transitions in Pure and Hybrid Hydrogels: A Fluorescence Study

“…As the polymerization progresses pyranine can have a chance to bind the polymeric system over two or three functional groups. Here a considerable shift from 508 to 380 nm occurs, as previously observed, [20,21] in the emission spectra when the OH group in pyranine binds covalently to the vinyl group of the growing AAm and NIPA polymer chains. At the same time, the shift in the short-wavelength peak between 380 and 427 nm is due to electrostatic binding of SO À 3 groups on pyranine to the AAm and/or NIPA monomers with protonated amide groups, whether on the same polymer molecule or on the other polymer chains.…”

“…The shifts in the emission spectra of pyranine during the polymerization [13] give more information about the microscopic nature of the polymer-probe interaction as was already described in our previous study. [20] In that study, we proved that the probability of bonding pyranine to the system over more than one functional group may increase with increasing polymer concentration and also with the reaction time. As the polymerization progresses pyranine can have a chance to bind the polymeric system over two or three functional groups.…”

“…The results showed that pyranine can be used as a probe for realtime monitoring of polymerization of the AAm system since it monitors both the progress of the polymerization via chemical binding using OH group and the change in the local density of the polymerizing sample by means of the gradual red shift in the short-wavelength-peak via ionic interactions over SO À 3 groups. [20] Figure 2a-c present the fluorescence intensity of the 512 nm peak, I 512 (corresponding to free pyranine in the sample cell) for the neat AAm, neat NIPA and their hybrids, respectively. Here neat AAm and neat NIPA are added for comparison.…”

Estimation of the Generation and the Weight Fraction of Dense Polymer Regions in Heterogeneous Hydrogels

“…In the synthesis, the polymer chains were chemically linked to the pyranine via radical addition during gelation. [36][37][38] The gels prepared in this way thus were charged with both positive and negative ions: SO À 3 side groups linked chemically to the polymer chains as subgroups of the pyranine, and Na þ counterions that were free in the gel. The covalent binding mechanism of the pyranine to the polymer strands is described in recent literature in detail.…”

Conductivity Percolation of Carbon Nanotubes in Polyacrylamide Gels

“…Here at first the shift from 512 nm to 380 nm in the emission spectra due to a C-O ether bond formation between the hydroxyl oxygen of 3sPyOH and a terminal C-atom of the growing AAm chain. Then the shift in the short-wavelength peak between 380 and 427 nm is probably due to the complexation of 3 SO  groups with protonated amide groups whether on the same polymer molecule or on the other polymer strands (Yılmaz et al, 2009). The reason for the shift in the isoemissive (isostilbic) point is the change in the internal morphology of the system: at the beginning of the polymerization the system is in the "sol" state (all pyranine are free) and above a certain time it turns into the "gel" state (most of pyranine are bonded).…”