STUDY OF SELF-ASSOCIATING AMPHIPHILIC COPOLYMERS AND THEIR INTERACTION WITH SURFACTANTS

The self-association of copolymers of N-isopropylacrylamide and N-n-oc tadecylacrylamide (Pnipam-C18) in aqueous solutions was studied by mea ns of time-resolved fluorescence quenching. The discrete domains consi st of several polymer chains interacting through their hydrophobic sid e chains, since the number of aliphatic side chains involved in the mi crodomain formation (aggregation number) is larger than the number of aliphatic side chains per polymer. By means of titration microcalorime try, the interaction of the copolymer with surfactants was studied. St rong association between the copolymer and the cationic surfactants N- cetylpyridinium chloride (C1GPyCl) and cetyltrimethylammonium bromide (CTAB) occurs by partitioning of the surfactants in a noncooperative m echanism. Prior to mixed-micelle formation, individual surfactant mole cules adsorb to collapsed polymer coils as can be seen from the large exothermal contribution in the enthalpy curves which result from micro calorimetric titration of surfactant into aqueous Pnipam-C18 solutions .