Pentablock Ionomer Based TEOS-TIP Hybrid Nanocomposites: Morphology, Physical Properties, and Ion Transport

Wednesday, 31 May 2017: 11:40
Grand Salon C - Section 16 (Hilton New Orleans Riverside)
F. Huang, W. Zheng, and C. Cornelius (University of Nebraska-Lincoln)
Nowadays, pure materials cannot embody all the physical, chemical, and mechanical properties required for a given application. Therefore, hybrid inorganic-organic composite materials were created to fill this critical void. The hybrid composites depend not only the properties of individual components, but also on the interfacial interactions between inorganic and organic phases. The significance of this work is to control the interaction-structure-property relationships of hybrid inorganic-organic nanocomposites in many applications such as fuel cells, lithium-ion batteries, biomimetic actuator, and water purification.

The PBC based hybrid organic-inorganic films were synthesized based on tetraethylorthosilicate (TEOS), titanium isopropoxide (TIP), and poly(t-butylstyrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-t-butylstyrene) or pentablock copolymer (PBC) via sol-gel chemistry. A ternary phase diagram was estibalished to understand the homogeneity of TEOS-TIP sol-gel system dependent on initial sol composition and reaction conditions leading to controllable materials. All hybrid PBC-TEOS-TIP membranes exhibited higher water uptake than unmodified PBC membranes. Proton conductivity increased 80% from 58 mS/cm for unmodified PBC film to 85 mS/cm for hybrid nanocomposite film due to the role TEOS-TIP within it. This can be attributed to the partial charge transfer from the titanate’s inorganic domains to sulfonate groups that promote acid dissociation and proton attraction. The PBC’s microphase-separated morphology changed from well-ordered lamella-like structure to a random and homogenous distribution of ionic domains with increasing TIP concentration, which was observed from AFM and SAXS results. TGA analyses revealed a decrease in degradation temperature due to titanate's catalytic character, and DMA results demonstrated reduced polymer chain mobility caused by inorganic-organic interactions. Finally, these PBC-TEOS-TIP hybrid composites were used as proton-exchange membranes (PEM) for hygroden fuel cells.