Pyrene-labeled poly(N,N-dimethylacrylamide)s were prepared by radical copolymerization
of N,N-dimethylacrylamide with N-(1-pyrenylmethyl)acrylamide. The progress of the copolymerization
reaction was followed by 1H NMR to ensure that the pyrene-labeled monomer was homogeneously
incorporated into the polymer backbone. Since pyrene is hydrophobic and poly(N,N-dimethylacrylamide)
is water-soluble, a set of water-soluble associative polymers was generated. The effect of solvent quality
toward these associative polymers was investigated. The level of association and the kinetics of encounter
between pendants were determined in N,N-dimethylformamide (DMF), acetone, water, and mixtures of
acetone and water. Analysis of the fluorescence decays with a blob model yields quantitative results
which agree with the qualitative information retrieved by other techniques (static light scattering, intrinsic
viscosity, UV−vis absorption). The level of association between hydrophobic pendants was found to be
small in acetone (a good solvent for pyrene). It increases when water is added to the solution, since pyrene
is insoluble in water. The level of association is smaller in DMF than in acetone, because DMF is a
better solvent than acetone for the polymer, and swelling of the polymer coil results in a decrease of the
interactions existing between the pyrene groups.
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