Engineering side-chain of T-shaped reactive molecules, and its effect on the retardation dispersion and biaxiality

T-shaped reactive molecules with different chemical structure of side-chain were newly synthesized, and retarder films were fabricated using a mixture of a rodlike reactive mesogen (RM) and the T-shaped molecules. The in-plane retardation and the dispersion of retardation of the retarder films were measured. The retarders made from the TRM molecules with the side-chain of stilbene, dibenzothiophene, benzene and naphthalene showed a positive dispersion (PD) of retardation. On the other hand, the retarder made from the TRM molecule with the side-chain of anthracene represented a negative dispersion (ND) of retardation. From out-of-plane retardation and UV–Vis absorption anisotropy measurements, the anthracene of the TRM molecule was found to be aligned orthogonal to the rubbing direction, i.e., parallel to the ordinary refractive index direction, contributing the rapid dispersion of the ordinary refractive index and the ND of retardation.