| Organometallic block copolymers, wherein one block is composed of alternating ferrocene and dialkylsilane units in the main chain, undergo self-assembly to form microphase-separated ordered structures similarly to typical organic block copolymers. The 1,1'-dimethylsilylferrocenophane monomer was synthesized and polymerized anionically with other monomers to make a variety of different organometallic block copolymers. The phase behavior and thermodynamic interactions of anionically synthesized poly(styrene-block-ferrocenyldimethylsilane) (SF) and poly(isoprene-block-ferrocenyldimethylsilane) (IF) copolymers were examined using depolarized light scattering, small angle x-ray and neutron scattering (SAXS and SANS), and transmission electron microscopy. The temperature-dependence of the Flory-Huggins parameter, chi, and the statistical segment lengths of SF and IF copolymers were determined by SAXS and SANS using the random phase approximation.; The thermodynamic interactions in poly(ferrocenyldimethylsilane) diblock copolymers were systematically adjusted by oxidizing the ferrocene moieties with silver salts and examined using SAXS and depolarized light scattering. The polymers retained microphase separated ordered structures upon oxidation and showed systematic changes in the location of the order-disorder transition as a function of extent of oxidation. By controlling the redox properties of the ferrocene moiety in the backbone of the polymer, we present a method for controlling the self-assembled microstructure and hence bulk material properties.; Using electrochemical techniques, a novel means of controlling the order-disorder transition of block copolymers was discovered. By applying very small electrical potentials to disordered solutions of organometallic block copolymers, oriented ordered grains were formed near one electrode, the result of electrochemical reactions. After reversing the electrical bias on the system, the ordered grains disappeared and new oriented ordered regions were formed at the opposite electrode. Our work establishes a fundamentally new mechanism for controlling the self-assembly of block copolymers. |
