Abstract
The fluoresence intensity of dansyl residues attached to poly(acrylic acid) (PAA) increases sharply when PAA forms complexes with polyoxyethylene (POE) or poly(vinyl pyrrolidone) (PVP), because the emission from this chromophore is more intense in organic media than in water. Fluorescence data could therefore be used to study complexation equilibria as a function of the ratio of PAA to the polymers acting as hydrogen bond acceptors, the chain length of the POE or PVP, pH and concentration of added salt. PVP was found to form more stable complexes than POE and one vinyl pyrrolidone residue seems to complex with one acrylic acid unit. Similar studies with labelled poly(methacrylic acid) (PMA) can be carried out only at pH values where the PMA chain is expanded, but then it forms more stable complexes with PVP than does PAA. After addition of unlabelled PAA to a solution in which dansyl-labelled PAA is complexed with POE or PVP, the decrease in the emission intensity accompanying complex interchange can be followed kinetically. These processes are biphasic.
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