Polyferrocene Diblock Copolymers: Synthesis, Self-Assembly and Morphology Characterizations

Abstract

This thesis describes the synthesis and self-assembly of a series of novel polyferrocenylsilane block copolymers. Polyferrocenyldimethylsilane-' b'-poly(propylene sulfide) (PFDMS-'b'-PPS) copolymers were synthesized by anionic polymerization via a "carbanion pump" strategy. Polyferrocenyldimethylsilane-'b'-poly([epsilon]-benzyloxycarbonyl-L-lysine) (PFDMS-'b'-PZLL) copolymers were synthesized by the ring opening polymerization of [epsilon]-benzyloxycarbonyl-L-lysine N-carboxyanhydride, initiated with amino-terminated PFDMS. In bulk, PFDMS-'b'-PZLL behaves as coil-rod block copolymer. An asymmetric PFDMS-'b'-PZLL sample formed a hexagonal-in-lamellar morphology, referring to the hexagonal packing of the [alpha]-helical PZLL and the phase-segregation of the block copolymer into a lamellar structure. This morphology originates from the liquid crystalline behavior of the PZLL. In dimethylformamide (DMF), a selective solvent for the non-PFDMS blocks, PFDMS-'b'-PPS, PFDMS-'b'-PZLL and polyferrocenyldimethylsilane-' b'-poly([gamma]-benzyl-L-glutamate) (PFDMS-'b'-PBLG) copolymers formed rod-like micelles, driven by the crystallization of the PFDMS. The presence of small amounts of a common solvent, tetrahydrofuran (THF), led to the formation of longer micelles or micelles with a better shape regularity. For PFDMS-'b'-PBLG, rod-like micelles formed in NaCl-saturated DMF. Without NaCl, only large irregular clusters were obtained. Plate-like micelles were prepared from polyferrocenyldimethylsilane-' b'-poly(L-sodium glutamate) (PFDMS-b-PLGNa) copolymers in water in the presence of THF. THF is a good solvent for the core-forming PFDMS and a non-solvent for the corona-forming PLGNa, and helps to promote the formation of these plate-like micelles. Block co-micelles were prepared from various combinations of the PFDMS block copolymers. A spatially selective functionalization of the block co-micelles with inorganic nano-particles was demonstrated. The self-assembly morphologies of polyferrocenylsilane-'b'-polydimethylsiloxane (PFS-'b'-PDMS) copolymers were studied with transmission electron microscopy (TEM). An usual contrast inversion was observed during the TEM measurements, which was possibly caused by electron beam radiation-induced cross-linking of the PDMS. It was also observed that the interfaces of PFS-' b'-PDMS copolymers can be preferentially stained with RuO4 vapor. The effect appears to arise from a competition between reactivity and diffusion.