Associative Polymer-Polymer and Polymer-Surfactant Systems: Phase Behaviour and the Influence of Chemical Reactions

Sammanfattning: Aqueous mixtures of two non-ionic polymers, poly(acrylic acid) (PAA) and the amphiphilic triblock copolymer, (EO)27(PO)67(EO)27, known by its trade name Pluronic® P104, showed an associative phase separation (miscibility gap), which decreased with the decrease of PAA length. It was found that PAA is a much less selective “solvent” to P104 molecules than water. P104 aggregates are disintegrated and thus the liquid crystalline structures are destroyed upon replacement of water by PAA. Oppositely charged polyelectrolytes, DNA (double- or single-stranded) and two cationic derivatives of the hydroxyethyl cellulose (cat-HMHEC and cat-HEC) were mixed in water. An asymmetric associative phase separation was observed: small amounts of cat-(HM)HEC could precipitate DNA but large amounts of DNA were needed to precipitate the polycations. The rheological properties of the off-stoichiometric one-phase mixtures were investigated. The viscosity increased as the polymer content was increased and showed an interesting non-monotonic behaviour for the cat-HEC/dsDNA/H2O system. Redissolution of insoluble polyion-surfactant ion complex salts by adding excess surfactant was investigated using the simple approach of preparing the complex salts and mixing them with excess surfactant. The complex salts contained poly(acrylate) homopolymer or copolymers containing acrylate and NIPAM or DAM. The phase diagram for the long homopolyions systems presented a large miscibility gap, while efficient redissolution was obtained for shorter polyions. Incorporation of neutral units (more hydrophobic) originated efficient redissolution. Polymerizations in surfactant systems were performed. The acrylate counterion to the surfactant ion was polymerized under conditions where the growing poly(acrylate) chain was the sole counterion to the surfactant ion aggregates. Therefore the equilibrium phase diagrams constructed using the complex salts and excess surfactant predict the result of different pathways from polymerization reactions: phase diagrams come alive. The structure of the polyion-surfactant ion concentrated phase was changed in situ through the degradation of the surfactant into alcohol. The used cationic surfactant (decyl betainate) had a hydrolyzing ester group sensitive to high pH. The degradation of the surfactant into decanol changes the curvature of the ordered structure of the concentrated phase. Multi-lamellar nano-particles were obtained.

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