Molecular orientation and dynamics in ferroelectric diblock copolymers monitored by FT-IR spectroscopy

In ferroelectric liquid crystalline block copolymers the properties of ferr oelectric liquid crystals (LC) are combined with those of diblock copolymer s: hence, one observes in these materials a microphase separation between t he amorphous polymer (polystyrene [PS]) and the ferroelectric liquid crysta l segment. The latter group can be switched by applying an external electri c field (<10(4) V cm(-1)). FT-IR spectroscopy (time-resolved) was employed to study structure and dynamics in these systems. From analysis of the dich roism of the FT-IR spectra, it was concluded that the components in the PS microphase are oriented randomly while the liquid crystalline groups form a n ordered phase. Time-resolved measurements of the switching of the LC bloc k were performed during the application of an external electric field. It m ay be shown that switching is of an electroclinic type and that the tilt an gle and the mesogenic motion increase with temperature, especially if the P S block is heated above T-g. The orientation of the LC block after heating to the isotropic phase is completely restored due to the memory effect of t he polymer microstructure.