Hydrogen bond donor/acceptor mixed-solvent systems for solutes that exhibit strong specific interactions are not readily characterized with methods that depend On solvatochromic parameters. In this work; the reaction of two monomers, 4,4'-oxidianiline (ODA) and pyromellitic dianhydride (PMDA), to form the common engineering plastic precursor, poly(amic acid) (PAA), are studied for the tetrahydrofuran (THF) mixed-solvent Systems (THF-methanol, THF-ethanol, THF-water) with spectroscopy. Solute-centric (SC) Kamlet-Taft solvatochromic (K-T) parameters for the solvent environment around the monomer are determined using a proposed model that incorporates spectroscopically determined local composition (X-L) around the ODA monomer and the preferential solvation Model. For the example reaction to occur under homogeneous conditions, mixed solvent conditions need have I-IBA-rich local compositions (0.30 < X-HBA(L) < 0.83); high solute-centric basicity (beta(SC) > 0.60), high Solute-centric polarity, (pi(SC)* > 0.63), and low solute-centric acidity (alpha(SC) < 0.63). The method developed allows characterization of mixed-solvent effects and can be readily extended to other systems that have strong specific interactions.