Viscoelastic properties of poly(styrene-co-vinylphosphonate) ionomers
Viscoelastic properties of neat and glycerol plasticized poly(styrene-co-diethyl vinylphosphonate) ionomers were investigated. Nanophase separation of a polar phase occurred due to hydrogen bonding or ionic interactions in the acid derivatives and the metal salts, respectively. Metal–phosphonate ion–dipole interactions were much stronger and more temperature persistent than the hydrogen bonding in the phosphonic acid derivatives, which were manifested by a much broader rubbery region in their viscoelastic behavior. The phosphonate interactions were thermally stable up to >250 °C, and the physically crosslinked network produced suppressed viscous flow of the ionomers to very high temperatures. Time–temperature superposition was not applicable for the SVP ionomers even at an ion content as low as 2.4 mol%. The addition of a polar plasticizer, e.g., glycerol, preferentially solvated the ionic associations and diminished the extent of the rubbery plateau of the ionomer and substantially decreased the terminal relaxation time.