Decoupled ion conduction in poly(2-acrylamido-2-methyl-1-propane-sulfonic acid) homopolymers

Abstract

A family of novel sulfonate based homopolymers has been prepared by partially replacing sodium cations with different types of ionic liquid ammonium counter-cations, leading to an increased degree of decoupling of the conductivity from the glass transition of the ionomers.

Sodium ion dynamics in a sulfonate based ionomer system studied by 23Na solid-state nuclear magnetic resonance and impedance spectroscopy

“…2). This corresponds to the mid-point of the glass transition temperature T g , and the onset for this transition was estimated as 56 C. This is significantly lower than the T g s reported for a previous series of Nacontaining PAMPS-based ionomers recently studied by our group (93 C for a co-polymer of PAMPS and poly(vinyl sulfonate) with Na + and N 1222 in a 2:8 ratio [31], 133 C for a PAMPS homopolymer also with Na and N 1222 in a 2:8 ratio [32]). This can be attributed to the larger co-cation, which has the effect of lowering T g by reducing the number of cross-links as demonstrated by Colby and co-workers [23,24].…”

“…This particular composition was chosen for two reasons. First, Noor et al have recently shown that PAMPS samples with mixed Na and tetraalkylammonium cations generally show higher overall conductivities at lower sodium concentrations [32]. Second, the lithium analogue [N 114(2O1) ] 0.8 [Li] 0.2 has recently been characterised by our group using similar experimental techniques [35], thus this composition allows a direct comparison to be made with both the lithium and non-ether containing equivalents.…”

“…An ionomer system based on the poly(2-acrylamido-2-methyl-1-propane-sulfonate) (PAMPS) monomer and containing Na + and dimethylbutylmethoxyethyl ammonium (N 114(2O1) ) cations in a molar ratio of 2:8 was synthesised according to the literature [31,32]. This particular composition was chosen for two reasons.…”

“…In a co-polymer system with poly(vinyl sulfonate) (PVS), impedance measurements showed that the conductivities increased with decreasing Na + content, with the highest values measured for the [PAMPS-N 1222 ] 0.9 [PVS-Na] 0.1 composition [31]. PAMPS homopolymers were also studied with different Na + content and different quaternary ammonium cation sizes [32]. Crucially, in these studies significant conductivities were measured below T g , indicating the decoupling of the cation mobility from the polymer dynamics.…”

“…Very recently, Noor et al studied a series of PAMPS-based systems containing both Na + and the methyltriethyl ammonium cation (N 1222 , where the subscript numbers indicate the number of carbon sites in each alkyl chain) [31,32]. In a co-polymer system with poly(vinyl sulfonate) (PVS), impedance measurements showed that the conductivities increased with decreasing Na + content, with the highest values measured for the [PAMPS-N 1222 ] 0.9 [PVS-Na] 0.1 composition [31].…”