POLYMER-INDUCED MICROSTRUCTURAL TRANSITIONS IN SURFACTANT SOLUTIONS

The interactions of nonionic polymers poly(vinyl methyl ether) (PVME), poly(propylene oxide) (PPO), poly(acrylic acid) (PAA), and ionic poly(sodium 4-styrenesulfonate) (PSS) with the wormlike micelles in aqueous solutions of nonionic hexaethylene glycol monohexadecyl ether (C(16)E(6)), pentaethylene glycol monododecyl ether (C(12)E(5)), and cationic surfactant cetyltrimethylammonium bromide (CTAB)/sodium salicylate (NaSal) have been investigated by cryo-transmission electron microscopy and shear theology. Ah the surfactant solutions were viscous, wormlike micellar solutions in the absence of polymers. The hydrophobic nonionic PPO induced a wormlike micelle to ribbon-shaped discoid micelle transition in C(16)E(6) solution, and there is no appreciable change in C(12)E(5) upon the addition of PPO and PVME. The results indicate the surfactant-polymer interaction is enhanced with an increase in surfactant alkyl chain length. Both PVME and PPO induced a wormlike-to-spherical micelle transition in the CTAB/NaSal solution. The contrast in the transitions between the C(16)E(6) and CTAB with PPO addition is due to the difference in the head groups which results in a difference in where the polymer resides in the surfactant aggregates. PSS has little effect on the C(i)E(j) systems, and PAA does not destroy the wormlike micelles of the C(i)E(j) before precipitation. The effects of nonionic polymer are interpreted in terms of the theory developed by Nagarajan.