A New Route To Stabilize the Smectic C Phase in a Series of Laterally Attached Side-Chain Liquid Crystalline Polynorbornenes with a One-Carbon Spacer

A series of polynorbornenes (PNBEs) with 1,4-bis[(3‘-fluoro-4‘-n-alkoxyphenyl)ethynyl]benzene mesogens (n = 9−12) laterally attached to the polymer backbone through a one-carbon spacer were previously synthesized by ring-opening metathesis polymerization of the corresponding norbornene-based monomers. Wide-angle X-ray diffraction (WAXD) experiments demonstrate that the mesogens organize into the tilted layer structure of a smectic C (SC) phase at room temperature, and polarized light microscopy demonstrates that the highest temperature ordered phase is a nematic (N) phase. Upon heating above room temperature, the tilt angle of the SC phase of all of the PNBEs (n = 9−12) continuously decreases, especially at temperatures above 70 °C for the PNBEs (n = 9−11) and 60 °C for the PNBE (n = 12). However, the SC phase of the PNBEs (n = 9−11) transforms to a N phase before the tilt angle reaches zero. That is, the SA phase is never actually achieved in the PNBEs (n = 9−11), although the decrease in the tilt angles...