Competition and Promotion between Two Different Liquid-Crystalline Building Blocks: Mesogen-Jacketed Liquid-Crystalline Polymers and Triphenylene Discotic Liquid Crystals

Abstract

Mesogen-jacketed liquid-crystalline polymers (MJLCPs) containing two triphenylene (Tp) units in the side chains, denoted as PPnV (n = 3 or 6, which is the number of the methylene units between the terephthalate core and Tp moieties in the side chains), were synthesized through conventional free radical polymerization, and the phase behaviors of these new combined main-chain/side-chain liquid-crystalline (LC) polymers were investigated. The chemical structures of the monomers were confirmed by elemental analysis, high-resolution mass spectrometry, and 1H/13C NMR. The molecular characterizations of the polymers were performed with 1H NMR, gel permeation chromatography, and thermogravimetric analysis. LC behaviors of the polymers were investigated by differential scanning calorimetry (DSC), polarized light microscopy, and wide-angle X-ray diffraction (WAXD). Both polymers exhibit excellent thermal stabilities. DSC and WAXD results indicate that covalently incorporating Tp discotic liquid crystals has a tremendous effect on the LC behaviors of MJLCPs. As expected, the glass-transition temperature decreases as the spacer length increases. Both polymers form rectangular columnar (ΦR) phases at relatively high temperatures. At low temperatures, however, Tp moieties in the side chains form a discotic nematic (ND) phase in conjunction with the ΦR phase developed by the rod-like supramolecular mesogen – the MJLCP chain as a whole, owing to the self-organization of the Tp moieties. For PP6V in particular, a higher symmetry hexagonal columnar (ΦH) phase forms when temperature exceeds 225 °C. Individual ordered structures developed by these two LC building blocks are not only competitive but also promotive to each other.

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

“…The synthetic route for PP12V is analogous to that previously reported for PP n V ( n = 3 or 6) and is depicted in Scheme . Details of the experimental procedures can be found in the Supporting Information.…”

“…Similar hierarchically ordered nanostructures are obtained by altering the calamitic mesogen from biphenyl to azobenzene . A similar molecular design incorporates triphenylene (Tp), a model discotic mesogen, into the side chains of PDAVT in our previous study . Tp moieties and the terephthalate core are linked via 3 or 6 methylene units as flexible spacers (polymers denoted as PP n V, n = 3 or 6).…”

“…Indium tin oxide (ITO) substrate was sequentially cleaned by detergents, deionized water, acetone, and isopropanol, and it was then dried in nitrogen at ambient temperature. All other materials were pretreated as previously reported …”

POSS-Containing Jacketed Polymer: Hybrid Inclusion Complex with Hierarchically Ordered Structures at Sub-10 nm and Angstrom Length Scales

“…15,16 MJLCPs are rod-like polymers with excellent tunability, 14,17 and they have also been used as rod blocks in constructing block copolymers with various self-assembled structures. 18−21 Polyhedral oligomeric silsesquioxane (POSS), which is often regarded as the smallest silica nanoparticle with a diagonal length of approximately 1.0 nm, is a versatile nanobuilding block that is rigid and shape persistent with various peripheral functionalities.…”

Synthesis and liquid crystalline behavior of side chain liquid crystalline polymers containing triphenylene discotic mesogens with different length flexible spacers

“…Two series of Tp-containing polyacetylenes with different peripheral chain lengths [34] and with different flexible spacers [36] show a typical hexagonal (Φ H ) phase. A series of mesogenjacketed liquid crystalline polymers (MJLCPs) containing two Tp units with different lengths of the methylene units between the terephthalate core and Tp moieties in the side chains can exhibit a variety of LC phases with variation of temperature [37,38] .…”