Molecular structure of polyelectrolyte/surfactant complexes vs. polymer tacticity
Introduction
Natural or synthetic polyelectrolytes can be complexed in aqueous solutions by ionic surfactants through electrostatic interaction between the oppositely charged sites of both constituents [1], [2], [3], [4]. Under stoichiometric conditions, the resulting complex is no longer soluble in water but becomes soluble in organic solvents. From these solutions, films can be cast in which the complex forms ordered structures [5], [6], [7], [8] as has been observed with polystyrene sulphonate. So far, studies on polystyrene sulphonate have been restricted to the atactic variety of this polymer [9]. Here, neutron scattering data obtained in the solution state (in n-butanol) and the gel state (nitrobenzene) are presented for two different tacticities of the polymer moiety, atactic (aPS) and isotactic polystyrene (iPS).
Section snippets
Experimental
Perdeuterated styrene was purchased from EURISOTOP and used after proper distillation. Perdeuterated n-butanol and perdeuterated nitrobenzene were also purchased from EURISOTOP, and used without further purification. Protonated cetyltrimethylammonium bromide (CTABH) was obtained from Fluka, hydrogenous n-butanol and hydrogenous nitrobenzene were from Aldrich. Perdeuterated atactic polystyrene was synthesized by classical anionic polymerization (Mw=105 with Mw/Mn=1.26). Perdeuterated isotactic
Solutions in n-butanol
Solutions in n-butanol have been prepared for concentrations ranging from Ccomp=0.018 g/cm3 to Ccomp=0.037 g/cm3. No effect of concentration has been detected. The scattering curves obtained for solutions in perdeuterated n-butanol are drawn by means of a Kratky-plot (q2IA(q) vs. q) in Fig. 1 for iPSSD/CTAH systems for aPSSD/CTAH systems. There is an important outcome as there is no effect of the polymer tacticity: the molecular structures of either complexes are identical in the explored q
Conclusions
The results highlight the absence of the effect of the polymer moiety tacticity on the molecular structure of polystyrene sulphonate/CTAB complexes in solutions. Evidently, the surfactant determines the molecular structure. Conversely, polymer tacticity influences the organization of the gel state. While lamellar structure seems to occur for complexes prepared from atactic polystyrene sulphonate, a much poorer order seems to set in for gels produced from isotactic polystyrene sulphonate.
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Cited by (3)
Influence of polymerization degree on the dynamic interfacial properties and foaming ability of ammonium polyphosphate (APP)-surfactant mixtures
2021, Journal of Molecular LiquidsCitation Excerpt :It is well known that the dynamic interfacial properties and foaming ability of the solution can be controlled by polyelectrolyte and surfactant [11–15]. The addition of surfactants can change the conformation of the polyelectrolyte chain [9,10,16]. Due to the strong electrostatic interaction, hydrophobic complexes are formed in solution, which affects the bulk phase and surface properties of the foaming solution [16–20].