Thermodynamic Interactions in Organometallic Block Copolymers

The thermodynamic interactions in anionically synthesized poly(styrene-blockferrocenyldimethylsilane) (SF) copolymers were examined using birefringence, small angle X-ray and neutron scattering (SAXS and SANS). We show that birefringence detection of the order-disorder transition is possible in colored samples provided the wavelength of the incident beam is in the tail of the absorption spectrum. The location of the order-disorder transition was confirmed by SAXS. The temperature-dependence of the Flory-Huggins parameter, χ, of SF copolymers, determined by SAXS, is similar in magnitude to that between polystyrene and polyisoprene chains. We find that χ is independent of block copolymer composition (within experimental error). We also demonstrate that the neutron scattering length densities of styrene and ferrocenyldimethylsilane moieties are identical due to a surprising cancellation of factors related to density and atomic composition.