Synthesis and characterization of linear AB diblock copolymeric styrenic-based energy conducting polymers with pendant ruthenium (II) trisbipyridyl chromophores

Homopolymeric Energy Conducting Polymers (ECPs) composed of a polystyrenic backbone with pendant trisbipyridyl chromophores (RuII, Os II) were previously synthesized and evaluated in collaboration with the Meyer group. Monte Carlo simulations and ultrafast spectroscopy experiments were used to evaluate these ECP's. Upon laser excitation of a mixed-loaded ECP, a RuII excited state formed, propagated via a series of efficient single-step RuII-RuII (>99%) energy transfer hops, and pendant OsII chromophores were efficiently sensitized (98%). The utility of these materials was limited by their inability to segregate into ordered morphologies and consequently, the poor control of the chromophore placement on a surface, in bulk, or in selective solvents.; This work has focused on the synthesis of block copolymeric scaffolds and metallopolymers to ameliorate the limitations of the previously studied ECPs. The synthesis of block copolymeric scaffolds was approached using living anionic and controlled radical polymerization techniques. Useful linear AB diblock copolymeric scaffolds were prepared successfully via Reversible Addition-Fragmentation chain Transfer polymerization (RAFT). The RAFT chain transfer agent, cumyldithiobenzoate, was used to prepare these scaffolds from styrene and t-BOC protected hydroxystyrene monomers. The t-BOC substituents were removed by acid hydrolysis to generate polystyrene-b-poly(4-hydroxystyrene) (PS-b-PSOH) copolymers.; RuII chromophores were attached to a series of PS-b-PSOH copolymers. A PS56-b-PSOH370 scaffold with 25--30% chromophore loading was prepared and found to be insoluble. A series of soluble metallopolymers were prepared using scaffolds with a much longer PS tail. Metallopolymer dissolution was improved when (1) both blocks were long (>200 repeats), (2) when the metal loading was maximized, and (3) unesterified phenolic repeat units were capped with acetic anhydride.