KINETIC CONTROL OF THE PHASE-SEPARATED STRUCTURE AND ELECTROOPTICAL SWITCHING PROPERTIES OF (POLYMER LIQUID-CRYSTAL) COMPOSITE FILMS PREPARED BY A SOLVENT-CAST METHOD

Methods of controlling the size and uniformity of low-molecular-weight liquid crystal (LC) channels or domains and the electro-optical switc hing properties were investigated for (poly(diisopropyl fumarate): (Pd i-iPF)/LC(E8)) composite films prepared by a solvent cast method from a homogeneous solution. The phase-separated structure was controlled o n the basis of the degree of intermolecular interaction between the ma trix polymer and the solvent. In the case of the composite film prepar ed from a mixed solution including a small amount of non-solvent to th e matrix Pdi-iPF, it was found from morphological observations that th e channel or domain sizes of E8 remarkably increased and the degree of distribution of E8 domain sizes decreased. From the rime-resolved lig ht transmittance and light scattering properties during solvent evapor ation. it was found that the resulting size and uniformity of the E8 c hannels or domains were strongly dependent on the degree of solubility between the solvent and the polymer. In other words, the size and uni formity of the E8 domains for the (Pdi-iPF/E8) composite film were str ongly dependent on the Pdi-iPF fraction co-existing in the E8-rich pha se at an early stage of phase separation which was induced by spinodal decomposition. Therefore, the electro-optical properties of the (Pdi- iPF/E8) composite films were directly dependent on the size and unifor mity of the E8 domains in the polymer matrix. The driving voltage decr eased with increasing size and uniformity of the E8 domains in the (Pd i-iPF/E8) composite film.