Influence of “Hydrophobicity” on the Composition and Dynamics of Polyelectrolyte Complex Coacervates

Abstract

Various types of specific interactions are believed to supplement the major entropic driving forces responsible for spontaneous liquid−liquid phase separations in mixtures of oppositely charged polyelectrolytes. Among these interactions, hydrophobicity has recently been probed experimentally via the synthesis and complex formation of polyelectrolytes bearing hydrophobic pendant groups or backbones. In this work, poly(4-vinylpyridines), P4VP, were N-alkylated with chains from one to six carbons in length. The fully alkylated polycations were complexed with poly(sodium methacrylate) to yield polyelectrolyte complexes or coacervates (PECs). Counterintuitively, PECs made with N-methyl to N-butyl P4VP were less stable to the addition of salt the longer the alkane chain, being easier to dope and having a lower critical salt concentration for dissolution. In contrast, the linear viscoelastic response of these PECs varied little. A transition in doping and properties was observed with N-pentyl and N-hexyl chains, the latter having a much higher modulus and much less sensitivity to salt concentration. Smallangle X-ray scattering suggested a new morphology for the N-pentyl and N-hexyl P4VP PECs, with interacting/phase separating alkane chains providing a transition into hydrophobicity-dominated PECs.

Hydrophobically modified complex coacervates for designing aqueous pressure-sensitive adhesives

“…42,66 Several research groups have investigated the influence of hydrophobicity on salt resistance, although not all of them came to the same conclusion. 40,42,43,46 Sadman et al 40 and Huang et al 46 found, similar to our work, that the salt resistance increased with increasing hydrophobicity. Huang et al showed an increase in salt resistance for the longest alkyl chains (6 to 12 carbons).…”

“…The effect of controlled hydrophobicity in the complex coacervates on the viscoelasticity has also been the subject of several investigations. 40,42,43 However, a systematic study to test whether or not a timehydrophobicity superposition principle holds for complex coacervates is less known, and therefore addressed in the present work.…”

Validity and Breakdown of Superposition Principles in the Viscoelasticity of Chitosan–Gum Arabic Complex Coacervates

“…Complex coacervates are liquid-like polyelectrolyte complexes (PECs), which can be obtained by mixing polycations and polyanions under specific conditions, depending on parameters like polyelectrolyte (PE) charge density, molecular weight, salt concentration, pH, and many others. , During the last decade, a lot of effort has been made to investigate the effect of various parameters on the viscoelasticity of complex coacervates, including temperature, , salt concentration, , pH, PE stoichiometry, PE molecular weight, , PE chemistry and hydrophobicity, , and the presence of cosolvents . For the majority of these parameters, although depending on the PE system and the parameter range, the spectra of the viscoelastic response can be superimposed.…”

Polyelectrolyte-multivalent molecule complexes: physicochemical properties and applications

“…[11][12][13] Beyond Schlenoff findings, as the systems become more complex, other factors such as hydrophobic interactions, hydrogen bonding, short-range interactions, and functional groups-dependent interactions come into play, and the interplay between these factors ultimately define the characteristics of the condensed phase. 10,14,15 Since any highly-charged macromolecule can be considered as a polyelectrolyte, an extensive variety of PECs with different characteristics and features can be designed from diverse building blocks, such as synthetic polyelectrolytes, natural polyelectrolytes, surfactants, proteins, nucleic acids, and peptides, among others. [16][17][18][19][20][21][22][23][24] As a general rule, macromolecular building blocks need to have enough electrostatic charges and to overcome a minimum molecular weight in order to condense into PECs.…”