Correlation length of hydrophobic polyelectrolyte solutions

• Published in: Europhysics letters Vol. 62; no. 4; pp. 588 - 594
• Main Authors: Baigl, D, Ober, R, Qu, D, Fery, A, Williams, C. E
• Format: Journal Article
• Language: English
• Published: Les Ulis IOP Publishing 01.05.2003; EDP Sciences; EDP sciences; European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing
• Subjects: 61.10.-i; 61.25.Hq; 82.35.Rs; Applied sciences; Condensed Matter; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Physics; Properties and characterization; Soft Condensed Matter; Solution and gel properties; Polyelectrolyte; Monodispersed polymer; Concentration effect; Styrenesulfonate polymer; Hydrophobic compound; Aqueous solution; Small angle X ray scattering; Experimental study; Power law; Correlation length; Molecular weight property relation
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/epl/i2003-00391-2

The combination of two techniques (Small Angle X-ray Scattering and Atomic Force Microscopy) has allowed us to measure in reciprocal and real space the correlation length ξ of salt-free aqueous solutions of a highly charged hydrophobic polyelectrolyte as a function of the polymer concentration $C_{\ab{p}}$, charge fraction f and chain length N. Contrary to the classical behaviour of hydrophilic polyelectrolytes in the strong-coupling limit, ξ is strongly dependent on f. In particular, a continuous transition has been observed from $\xi \sim C_{\ab{p}}^{-1/2}$ to $\xi\sim C_{\ab{p}}^{-1/3}$ when f decreased from 100% to 35%. We interpret this unusual behaviour as the consequence of the two features characterising the hydrophobic polyelectrolytes: the pearl necklace conformation of the chains and the anomalously strong reduction of the effective charge fraction.