AGGREGATION OF ASSOCIATING POLYMERS STUDIED BY F-19 NMR

The aggregation in aqueous solution of a hydrophobically modified poly electrolyte was investigated by F-19 n.m.r. The polymer studied was a poly(sodium acrylate) of average molecular weight 5000 bearing 8 mol% of -CH2C7F15 pendant alkyl chains. The F-19 n.m.r. spectra of the modi fied polymer displayed the characteristic features of slow exchange be tween the free and the aggregated states for the alkyl chains. It is t herefore possible to determine the respective fractions of free and ag gregated -CH2C7F15 groups by direct integration of the n.m.r. signals. This behaviour is opposite to the fast exchange occurring for classic al surfacants (sodium pentadecafluorooctanoate, SOF). The exchange pro cess in the polymer case is at least three orders of magnitude slower than in the surfactant system. (C) 1997 Elsevier Science Ltd.