| 초록 |
Most laterally attached side-chain liquid crystalline polymers (SCLCPs) synthesized thus far have exhibited only the nematic (N) phase. In order to search for laterally attached SCLCPs having a smectic C phase, a series of polynorbornenes (PNBEs) with 1,4-bis[(3´-fluoro-4´-n-alkoxyphenyl)ethynyl]benzene mesogens (n = 1 - 12) laterally attached to the polymer backbones through a one-carbon spacer was previously synthesized. According to the DSC results, PNBEs (n = 9 – 12) exhibit three thermal events: a broad transition and two overlapped first-order transitions. For n = 1 – 12, as the number of methylene units in the side chains decreases, the broad thermal transition becomes less obvious. Wide angle X-ray diffraction experiments reveal the tilted low-angle reflections for n = 12, indicating that the mesogens organize into a tilted layer structure of a smectic C phase at room temperature. The intensity and sharpness of low-angle reflections decrease with decreasing number of methylene units. The tilt angle of low-angle reflections decreases greatly from 70 ℃ for n = 9 – 11, and 60 ℃for n = 12 on heating. The tilt angle of n = 2 – 4 almost does not change. Therefore, the broad transition observed by DSC is associated with the change in the tilt angle. Polarized light microscopy shows that the highest temperature ordered phase is the N phase. The lower-temperature first-order transition observed for n = 9 – 11 is a smectic C and N phase transition. However, the smectic A phase is observed in fiber pattern of n = 12 around 85 ℃. |
