Executive Summary : | The research proposes a versatile design with periodic morphological changes in solid-state ion-exchange polymers (IEPs) for elevated performance in electrochemical (fuel cells) or electromechanical (polymer based robotic actuator) applications. These IEPs are used as ion conductors in these devices. An ideal IEP shall endure dynamic operating conditions without compromising on performance. Thus it is imperative to design adaptable and versatile IEPs. Irradiation is a cost-effective and simple technique, which can be used to transform the IEP surface morphology. An optimum level of irradiation is known to cause structural changes to IEPs, which lead to enhanced ionic conductivity. However, it drastically reduces strain-to-failure ratio by more than 100%, even though there is a significant enhancement in tensile modulus. As noted, among many well knows techniques, irradiation is one of the techniques that is widely used to alter morphological structure of polymer blends. However, all of these methods result in monotonic change in electric and mechanical properties of functional polymers. This will set a limiting criteria for operating range of these polymers and generally accepted as not very advantageous. On the other hand, a direct and continuous exposure of irradiation (in this study UV light) will result in significant reduction in toughness with increase in hardness. Therefore, a periodic, both in spatial as well as temporal domain, irradiation methodology is adopted to enhance ionic conductivity without compromising on the mechanical toughness. The project proposes a simple experimental method to impart temporal periodicity in irradiation on IEPs, which is expected to induce locally co-continuous structure. This non-continuous irradiation may result in varied cross-link density and elastic stress due to relaxation time. This technique may not provide periodicity in properties on the overall IEP membrane and hence spatial irradiation is proposed. The resulting IEP membranes will be tested for their enhanced functional capabilities in an electrochemical cell, i.e., polymer electrolyte fuel cell (PEFC). In order to assess the localized changes in electric properties (ionic conductivity), a customised multi-grid current sensor plate will be placed in-situ PEFC unit cell, which would quantify current density as a function of operating conditions. The magnitude of this current density is directly proportional to the ionic (proton or H+) conductivity, and hence this practical case will validate the influence of spatiotemporal irradiation on IEPs. Further, localized and average changes in electrical and mechanical properties will be quantified using standard equipments. Overall, the proposed technique provides a convenient way to impart property hotspots in IEPs, which not only retains original physical properties but also imparts a smoothly varying ductile to brittle zones and normal to high ionic conductivity. |