The binding of SDS to cellulose polymers in the semidilute concentration regime has been studied by means of NMR, ion-selective electrode, and a time-resolved fluorescence technique. Two polymers have been used, differing only in a low degree of hydrophobic modification of one of them. NMR self-diffusion and activity measurements show that the binding of SDS to the nonmodified polymer has a fairly pronounced critical aggregation concentration (cac), while binding to the hydrophobically modified polymer is less cooperative up to a concentration of about the cac in the nonmodified polymer/SDS system. NMR T 2 relaxation and fluorescence studies indicate that surfactants bound to the hydrophobically modified polymers in the non-cooperative regime have slow dynamics compared to micellized surfactants, to surfactants bound to the unmodified polymer, and to surfactants bound to the hydrophobically modified polymer in the cooperative regime. Furthermore, in the non-cooperative regime the fluorescence studies imply that the SDS aggregation number of the mixed micelles is low and that the number of hydrophobic zones is invariant with respect to the surfactant concentration.

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The interactions between various surfactants (anionic, cationic, and nonionic) and a nonionic ethyl(hydroxyethyl)cellulose (EHEC) polymer or a hydrophobically modified analogue (HM-EHEC) have been examined. The study has been performed as a comparative investigation between the hydrophobically modified polymer and the unmodified parent polymer using rheology. The rheological results have been analyzed with the aid of a simple modified Maxwell model. Information about the low-frequency behavior was extracted from this model, and the rheological features were presented in terms of the complex viscosity and a characteristic relaxation time. In the presence of an ionic surfactant, the rhelogical measurements revealed significant polymer/surfactant interaction for both EHEC and HM-EHEC, but the interaction peak, observed in the different rheological quantities, was more pronounced and located at a lower surfactant concentration for the hydrophobically modified polymer. In the presence of a nonionic surfactant, the polymer/surfactant interaction was weaker. By considering the temperature effect, an important difference in the polymer dynamics between the hydrophobically modified polymer and the unmodified analogue was established. The hydrophobically modified polymer shows a normal temperature dependency, while the motion of the unmodified analogue is slowed down with increasing temperature. The finding for the unmodified polymer is attributed to increased polymer/polymer attractions with an increased temperature. It has also been shown that the hydrophobically modified polymer has features regarding the formation and breakdown of the polymer/surfactant complex in common with other hydrophobically modified polymers (both nonionic and ionic). At a certain surfactant concentration the network starts to lose its connectivity, however, because of an increased surfactant aggregation number of the mixed micelles, the breakdown process is postponed when the surfactant chain length is increased.

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We report on the effects on the phase behavior, microstructure, and rheology in the water-rich part of the ternary nonionic surfactant system comprising pentaethylene glycol dodecyl ether (C12E5)−water−decane, on addition of poly(ethylene oxide) (PEO) and hydrophobically end-capped PEO (HM-PEO). The two polymers destabilize both the micellar and the lamellar phases. With PEO, a segregative phase separation is observed, while with HM-PEO, an associative phase separation is seen. The micellar phase containing HM-PEO was investigated by NMR relaxation and self-diffusion measurements and small-angle neutron scattering as well as low shear viscosity and oscillatory frequency sweep measurements. It was found that the polymer affected the intermicellar interaction, leading to an increased ordering of the micelles, while leaving the micellar size unchanged. Addition of HM-PEO (≤2 wt %) led to a drastic decrease of the micellar self-diffusion coefficient and additionally to an increase of the low shear viscosity by several orders of magnitude. The storage and loss moduli were successfully fitted to a single Maxwell element. Analysis of the fitted parameters and comparison with percolation theory yielded the fraction of polymers that interconnected the micelles (thus forming bridges) as well as the fraction of polymers that did not contribute to the connectivity of the network (resulting in loops).

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