Correlation Between Structure and Physical Properties of Sulfone-Containing Aromatic Polyimides

Sulfone-containing aromatic polyimides were prepared by chemical imidization using aromatic diamine and dianhydride as monomers. Polymers were synthesized through molecular design based on various monomer combi-nations for potential use as binders for lithium-ion batteries (LIBs). Solubility in N-methyl-2-pyrrolidone (NMP) for slurry production, insolubility in electrolyte, binding to current collector, and glass transition in a wide temperature range were evaluated for stable use in various process conditions and environments. The resulting polymers were all insoluble in the electrolyte and strongly adhered to copper and aluminum foils. As the rotational freedom and the degree of being kinked of the polymer chain increased, the solubility in NMP increased and the glass transition temperature (T_g) decreased. When the effect of hybridization state of the central element in the main chain on the rotational freedom and the effect of linkage position on the degree of being kinked were arbitrarily quantified, a specific relationship was established with T_g. This study is expected to provide a key molecular design guideline for construction of a binder-material library for LIBs by clarifying the correlation between the molecular structure and physical properties of sulfone-containing polyimides.