Sprecher
Beschreibung
Poly(ether ether ketone) (PEEK) is of particular interest in the design of chemically stable membranes for use in harsh environments due to its high temperature thermal transitions, high crystallizability, mechanical strength, and low chemical reactivity. Recently, we have discovered that PEEK can be dissolved at elevated temperatures in a non-toxic, benign solvent, 1,3-diphenylacetone (DPA). Upon cooling, these solutions form thermoreversible gels via a thermally induced phase separation (TIPS) process. Morphological analysis using small-angle scattering and scanning electron microscopy shows that these gels contain a hierarchical network of interconnected fibrils of axialitic crystals containing solvent swollen macro-scale and meso-scale pores. Upon introduction of a suitable functionalizing reagent (e.g., a sulfonating reagent), the functionalization is sterically limited to the amorphous chain segments between the crystalline lamella, resulting in a blocky microstructure of the resulting copolymer. Using this method of post-polymerization functionalization, we have synthesized blocky sulfonated SPEEK membranes with remarkably high proton conductivity, rivaling the benchmark Nafion for fuel cell applications. The high mechanical stability of these PEEK gels has also afforded the development of advanced aerogels by solvent extraction with remarkably low thermal conductivity, high porosity, and high surface area. We have also recently discovered that our new benign solvent is ideal for creating new mechanically robust aerogels from waste PET, providing a unique upcycling of single use packaging to long life-time insulation materials.