Eight series of poly(alkyl methacrylate)sbearing different sidechains and one series of poly(methyl acrylate) were randomly labeledwith pyrene, and their ability to form pyrene excimer was characterizedquantitatively by steady-state and time-resolved fluorescence to demonstratethat such measurements provide a quantitative measure of polymer chaindynamics (PCD) in solution. Each series of pyrene-labeled polymershowed increased excimer formation with increasing pyrene content,but the increase was more pronounced for the polymers known to bemore flexible based on their reported glass transition temperature(Tg). In the case of the poly(alkyl methacrylate)swith a linear side chain, a shorter side chain resulted in increasedexcimer formation. Replacing a linear side chain with a more rigidone containing the same number of carbon atoms resulted in decreasedmobility of the polymer. Fluorescence Blob Model (FBM) analysis ofthe fluorescence decays provided a more accurate representation ofthose pyrenes that formed excimer by diffusion and thus reflectedPCD more precisely. Global FBM analysis of the pyrene monomer andexcimer fluorescence decays yielded the blob size Nbloband the product kblob× Nblobwhich reflects PCD. Foreach series, both Nbloband kblob× Nblobremainedconstant with pyrene content. Their average value ⟨Nblob⟩ and ⟨kblob× Nblob⟩ decreasedsubstantially with increasing side-chain length, addition of the α-methylsubstituent to poly(methyl acrylate) to yield poly(methyl methacrylate),or increased rigidity of the side chain, demonstrating that an increasein bulkiness or stiffening of the side- or main chain is associatedwith a pronounced decrease in chain mobility. These experiments arethe first to demonstrate that pyrene excimer formation can be usedto characterize quantitatively PCD in solution in the same mannerthat Tgis being used to characterizePCD in the bulk. [ABSTRACT FROM AUTHOR]