Conformational transition of polyelectrolytes in mixed solvent by dielectric spectroscopy: Electrostatic and hydrophobic interactions

We studied conformational transition of poly(acrylic acid)-graft-dodecyl (PAA-g-dodecyl), and PAA-graft-poly(ethylene oxide)-graft-dodecyl (PAA-g-PEO-g-dodecyl) molecules in DMF/H2O solvent by dielectric analysis method utilizing a double-layer polarization theory. In addition to the hydrophobic interaction which has been demonstrated to be vital for their conformational transition with water content, it is confirmed that the electrostatic interaction is crucial. For PAA-g-dodecyl molecules, at a critical value of water content, a peak value of correlation length is reached originating from the delicate balance between electrostatic and hydrophobic interactions. For PAA-g-PEO-g-dodecyl molecules, chains conformation is mainly determined by electrostatic interaction over the entire range of water content due to the low content of dodecyl groups. Meanwhile, H-bond associative interaction prevents the dissociation of free carboxyl groups over the range of lower water content, thus their stretched transition moves to higher water content. Our results provide the underlying insights needed to understand solvent effect on the conformational transition for polyelectrolytes with hydrophobic groups. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019