Ordered nanostructures at two different length scales mediated by temperature: A triphenylene‐containing mesogen‐jacketed liquid crystalline polymer with a long spacer

Abstract

A mesogen‐jacketed liquid crystalline polymer (MJLCP) containing triphenylene (Tp) moieties in the side chains with 12 methylene units as spacers (denoted as PP12V) was synthesized. Its liquid crystalline (LC) phase behavior was studied with a combination of solution 1H NMR, solid‐state NMR, gel permeation chromatography, thermogravimetric analysis, polarized light microscopy, differential scanning calorimetry, and one‐ and two‐dimensional wide‐angle X‐ray diffraction. By simply varying the temperature, two ordered nanostructures at sub‐10‐nm length scales originating from two LC building blocks were obtained in one polymer. The low‐temperature phase of the polymer is a hexagonal columnar phase (ΦH, a = 2.06 nm) self‐organized by Tp discotic mesogens. The high‐temperature phase is a nematic columnar phase with a larger dimension (a′ = 4.07 nm) developed by the rod‐like supramolecular mesogen—the MJLCP chain as a whole. A re‐entrant isotropic phase is found in the medium temperature range. Partially homeotropic alignment of the polymer can be achieved when treated with an electric field, with the polymer in the ΦH phase developed by the Tp moieties. The incorporation of Tp moieties through relatively long spacers (12 methylene units) disrupts the ordered packing of the MJLCP at low temperatures, which is the first case for main‐chain/side‐chain combined LC polymers with MJLCPs as the main‐chain LC building block to the best of our knowledge. The relationship of the molecular structure and the novel phase behavior of PP12V has implications in the design of LC polymers containing nanobuilding blocks toward constructing ordered nanostructures at different length scales. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 295–304

Nanoindentation of Films of Perfluorotridecyl, Perfluorodecyl, and Perfluoroheptyl End‐Functionalized Polystyrene at the Micron Scale

“…This polymer has been shown to exist in four different helical crystalline states I–IV, depending on temperature and pressure and appears to be susceptible to rapid helix reversals at elevated temperatures . In agreement with the above, numerous polymers containing RF pendent‐ or end groups have been shown to exhibit mesogenic properties . In addition perfluorocarbons and RF groups have been shown to give exceptionally low‐surface free energies .…”

Influence of main chain on the phase behaviors of side‐chain liquid‐crystalline polymers with triphenylene mesogens of long alkyl tail substituents

“…The polymers adopted a columnar shape and self‐organized into a hexagonally packed columnar phase. Zhu et al discussed the LC behaviors of mesogen‐jacketed liquid‐crystalline polymers, containing two Tp units, with different number of methylene units between the terephthalate core and Tp moieties in the side chains . With increase in spacer length and temperature, the polymers exhibited interesting phase behaviors.…”

Columnar Phase-Forming Polymers

“…At high temperatures (>150 C), where the entropy has a greater influence, the whole polymer chains act as cylinders and organize in a columnar nematic phase, probably behaving as self-compacting chains. This is supported by the appearance of the isotropic phase when cooling the columnar nematic phase to around 150 C. Further cooling the isotropic phase to~130 C, a Col h phase appears, driven by the formation of TP π-stacks (Zhu et al 2014).…”