Effect of Pt(II) coordination on the thermotropic liquid‐crystalline behavior of poly(acrylic ester)s containing 4′‐cyano‐4‐biphenylyloxy mesogenic groups

Poly(acrylic ester)s 3a–f and 4a–g, containing 4′‐cyano‐4‐biphenylyloxy mesogenic groups coordinating to Pt(II) ions with various contents, were synthesized by ligand exchange reaction of poly(acrylic ester)s 1 and 2 with dichlorobis(benzonitrile)platinum (II). The effect of Pt(II) coordination of the mesogen on the thermotropic liquid‐crystalline behavior was examined by DSC, X‐ray diffraction, and polarizing microscopy. For polymers 1, 3a–c with a content x of 4′‐cyano‐4‐biphenylyloxy mesogen coordinating to the Pt(II) ion less than 24 mol‐%, a nematic mesophase was observed between Tg and Tc. For polymers 2, 4a–e with x < 20 mol‐%, a smectic mesophase was found between Tg and Tc. On the other hand, polymers 3d–f and 4 f and g with a high amount of mesogenic groups coordinating to the Pt(II) ion do not form mesophases due to the cross‐linked structure resulting from the coordination of the mesogen to the Pt(II) ion.