Metallopolymers as responsive materials: shifting equilibrium by tuning structure

This thesis describes the synthesis and characterization of a series of poly(ionic liquids) (PILs), or polyelectrolytes, from poly(ferrocenylsilane)s (PFSs) and their applications in responsive materials. PFSs are a fascinating class of metallopolymers, with a backbone consisting of alternating ferrocene and silane units. Redox-active ferrocene units provide unique redox-responsive properties, and the presence of silane groups offers great opportunities for post-polymerization modification. However, synthetic access to soluble, well-characterized metallopolymers with controllable properties, functionalities, and processability in aqueous media has proved to be a significant challenge. In this thesis, poly(ferrocenyl(3-iodopropyl)methylsilane) (PFS-I) was readily synthesized by transition metal-catalyzed ring-opening polymerization and employed as suitable precursor for post-polymerization modification because of the reactivity of its haloalkyl moieties, i.e. via the Menschutkin reaction or Strecker sulfite alkylation. Aiming at diversified functionalities that give rise to enhanced responsiveness to stimuli or even to multiple stimuli, a variety of substituents has been explored in this thesis. By tuning polymer structures and compositions, understanding the dynamic phase behavior, using different cross-linking chemistries, and applying external fields or constraints under appropriate processing conditions, a variety of applications are explored in this Thesis, including artificial muscles from electrospun hydrogel microfibers, porous membranes and micro-particles with breathing pores, an active plasmonic system from AuNP-hydrogel composites, carbon nanotube-hydrogel composites with bi-stable states and tunable resistance, an electrically switched smart window device, and symmetric redox flow batteries.