Session: POLY/PMSE Poster Session:

The formation of novel interpolymer complexes (IPCs) between poly(sulfonic acid)s and poly(ethylene oxide) (PEO) is reported. The complexes were precipitated from polymer mixtures in aqueous solution and depositated on surfaces as LBL films. The interpolymer association in poly(sulfonic acid)/PEO is ascribed to hydrogen bonding between the sulfonic acid and the ether of PEO, this characterization was confirmed from infrarred spectroscopy evidence. Sulfonic acids are very strong acids, they are fully dissociated. However, we show in this work that some poly(sulfonic acid)s can form ICPs with PEO both in solution and on surfaces, these complexes were precipitated from aqueous solutions and depositated on surfaces in a LBL procedure. The experimental evidence supporting the formation of IPCs of poly(sufonic acid)s and PEO is: (i) polymer precipitation is maximized for a 1:1 monomer stoichiometry and (ii) the two polymers can be sequantially deposited as LBL films, which require a complexation mechanism for assembly. Furthermore, IRRAS experiments demostrate the presence of both PEO and the Poly(acid)s in the films. The formation of IPCs with PEO was successful for poly(styrene sulfonic acid) PSSA and Nafion, but not for PVSA. We explain this result as the combination of two effects: PSSA and Nafion are expected to be more hydrophobic than PVSA because hydrophobic interactions are know to stabilize IPCs and hydrogen bonds in ether/aromatic-sulfonic acid complexes are predicted to be stronger than those in ether/aliphatic sulphonic-acid complexes. The interpolymer bonding in PSSA/PEO and Nafion/PEO was tentatively proposed to result from hydrogen bonding between the non-dissociated sulfonic acid groups (SO₃H) and the ether in PEO because in spectra of Poly(sulfonic acid)/PEO IPCs have an IR band at 3060 cm-1 that is absent in the spectra of the pure polymers. We explained the unexpected formation of PSSA/PEO and Nafion/PEO IPCs in terms of the strenght of the ether/sulfonic hydrogen bond and the fact that its formation displaces the sulfonic-acid/sulfonate acid-base equilibrium toward the protonated SO₃H species.

Federico Davia

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