Crystallization and phase behavior in hybrid organic-inorganic diblock and triblock copolymers with salt

Polymer electrolytes are a promising avenue to enable lithium metal anode batteries. Copolymer electrolytes have highly tunable nanostructures containing ion-conducting domains and mechanically rigid domains. The phase behavior of 2 poly(ethylene oxide) -b-polyhedral oligomeric silsesquioxane (PEO-POSS) diblock copolymers and 1 polyhedral oligomeric silsesquioxane -b-poly(ethylene oxide) -b-polyhedral oligomeric silsesquioxane (POSS-PEO-POSS) triblock copolymer mixed with lithium bis(trifluoromethane)sulfonimide salt are presented. While self-consistent field theory suggests that triblock copolymer architectures stabilize the disordered phase, the opposite case is true. Further, though we expect the increase of chain length stabilizes the ordered phases, we observe a wider disordered window in the larger diblock copolymer system. We postulate that POSS crystallization plays a large role in the phase behavior. POSS domains organize into well-ordered crystals in the triblock copolymer/salt mixtures, while POSS domains remain weakly crystalline or amorphous in the diblock copolymer systems.