Microphase behaviour of ferrocenyldimethylsilane-b-methylmethacrylate diblock copolymers

A series of narrowly distributed diblock copolymers from poly(1,1′-ferrocenyldimethylsilane) (PFS) and polymethylmethacrylate (PMMA) was prepared via anionic polymerisation and characterised with respect to their thermal and morphological behaviour in the bulk. TGA and DSC experiments reveal a high thermal stability of the block copolymers up to temperatures of above 220 °C. Homogeneous films (ca. 1 mm in thickness) were prepared from these materials by standard film-casting procedures followed by annealing at elevated temperatures. These films were characterised by transmission electron microscopy (TEM). Depending on the PFS volume fraction, ϕPFS (0.25≤ϕPFS≤0.48), the three classical microphase morphologies were found, i.e. the spherical, hexagonal and lamellar ones. Due to the strong segregation tendency of PFS and PMMA, no complex morphologies such as the gyroidic were found for the rather high-molecular-weight samples under investigation here. Instead, either the direct transition from the hexagonal into the lamellar morphology was observed when the PFS content crosses the critical value of ϕPFS=0.40, or the coexistence of these two morphologies was found.