| Abstract
| - We have determined the static and time-resolved fluorescence of a poly(dimethylsiloxane)(PDMS)-based three-armed junction that contains a single dansyl reporter group when it is dissolved atlow concentration in three normal liquids (good, ϑ, and poor solvents) and neat methyl-terminated PDMS.The junction results are compared to a “junctionless” analoguedansyl propylamine. We report on theactivation energies for dansyl thermal quenching and rotational reorientation and the dansyl residue'sability to reorient and precess at the junction point. In normal liquids a decrease in solvent quality leadsto a collapse of the junction's PDMS arms around the dansyl reporter group, an inhibition of the dansylresidue's ability to form its twisted intramolecular charge transfer state, and impedance of the dansylresidue's ability to reorient. When the junction is dissolved in neat methyl-terminated PDMS, there isevidence for chain-length-dependent interpenetration of the PDMS “solvent” molecules into the junctionand modulation of the local microenvironment surrounding the dansyl residue at the junction. Theseresults demonstrate the dramatic role solvent can play in tuning the local microenvironment thatsurrounds a polymeric junction point.
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