Abstract
This dissertation examines how changing the hyperbranching density and structure of
polymer host backbones affects the physical properties of solid state polymer electrolytes. The
structure of interest in this dissertation is the hyperbranching polymer backbone, which includes
tetrabranching and tribranching architectures of varying hyperbranching densities. For a series of
poly(ethylene glycol)-based polymers, we consider how molecular architecture impacts the
electrochemical, thermal, and mechanical properties of the electrolytes on both the bulk and
macromolecular scales. For both architectures, decreasing hyperbranching densities lead to
improved conductivities (tetra- at 9.45 • 10-4 S cm-1 and tri- at 1.95 • 10-3 S cm-1 at 80 ºC) and
improved shear storage moduli (tetra- at 0.63 MPa and tri- at 1.24 at 90 ºC). While having superior
ionic conductivity and shear strength, the tribranching electrolytes were not compatible with
lithium, which is a necessity for lithium-ion battery application. Following successful synthesis
and material characterization, the tetrabranching electrolytes of various hyperbranching densities
and structures are further probed as electrolytes in lithium-ion batteries. This series showed
improved cycling performance with decreasing hyperbranching density (specific capacity of 1175
mAh gSi-1 after 50 cycles), with improved energy storage capabilities relative to the liquid control
electrolyte (763 mAh gSi-1 after 50 cycles). Ultimately, the solid state polymer electrolytes
iii synthesized in this work are promising candidates for further use in energy storage devices due to
their observed thermal, electrochemical, and mechanical stabilities.