The role of Na+, Zn2+ cations on the mechanical, thermal and moisture permeation behaviors of poly(vinyl butyral) based ionomeric films

Abstract

In the present study, the inclusion of ionic moieties in the poly(vinyl butyral) matrix was accomplished by co-polymerizing butyraldehyde with poly(vinyl alcohol) and carboxy benzaldehyde in aqueous acidic medium. FT-IR and NMR spectroscopy results confirms the formation of acetal and butyral linkage in the polymer. Mechanical studies (both static and dynamic) of these ionomeric films show flexibility with ionic linkages up to 15 mol % acid neutralized with sodium and zinc ions. Zinc ionomers exhibit enhanced mechanical properties compared to sodium neutralized samples, because of its ionic size and ion-pair association within the multiplets. The moisture permeability studies accessed through calcium degradation test show the films with 15 mol % exhibit enhanced impermeability than other sodium ion neutralized films. The same trend was also observed for organic solar cells that are encapsulated with these films after exposure to external environment for 400 h. The water interaction with ionomer films was also evaluated at various temperatures and the results were presented based on the ionpair clustering and the steric hindrances in due of phenyl ring attachment to the base PVB matrix.