Interpolymer Complexes of Poly(Sulfonic Acid)s and Poly(Ethylene Oxide): An Unexpected Association

MALDONADO, LILIANA; DEBAIS, GABRIEL; DAVIA, FEDERICO; MÉNDEZ DE LEO, LUCILA; TAGLIAZUCCHI, MARIO

SOFT MATTER

ROYAL SOC CHEMISTRY

Año: 2019 vol. 15 p. 9318 - 9324

1744-683X

The formation of novel interpolymer complexes (IPCs) between poly(sulfonic acid)s and poly(ethylene oxide) (PEO) isreported. The complexes were precipitated from polymer mixtures in aqueous solution and deposited on surfaces as layerby-layer films. Based on evidence from infrared spectroscopy, the interpolymer association in poly(sulfonic acid)/PEO IPCsis ascribed to hydrogen bonding between the sulfonic acid and the ether in PEO. This interaction is not anticipated becausesulfonic acids are fully dissociated in aqueous solutions due to their strong acidity. Theoretical calculations suggest that theunexpected association of PEO and poly(sulfonic acid)s results from the formation of very strong sulfonic-acid/etherhydrogen bonds, which increase the apparent pKas of the poly(sulfonic acid)s and, therefore, decrease the net charge ofthese polymers. It is shown that while poly(styrene sulfonic acid) (PSSA) and Nafion form IPCs with PEO, poly(vynil sulfonicacid) (PVSA) does not. This result is explained in terms of the hydrodrophobic nature of PSSA and Nafion, which stabilizetheir IPCs, and the fact that hydrogen bonds in PSSA/PEO IPCs are predicted to be stronger than in PVSA/PEO IPCs.