Thermodynamic interactions in organometallic block copolymers:: Poly(styrene-block-ferrocenyldimethylsilane)

The thermodynamic interactions in anionically synthesized poly(styrene-block-ferrocenyldimethylsilane) (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, chi, of SF copolymers, determined by SAXS, is similar in magnitude to that between polystyrene and polyisoprene chains. We find that chi 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.