Structures and properties of liquid‐crystalline polymers based on laterally attached oligo p‐phenylenes

Abstract

The structures and properties of liquid‐crystalline polymers containing laterally attached p‐terphenyl and p‐pentaphenyl have been studied. In contrast to their mesogenic groups, that is, p‐terphenyl and p‐pentaphenyl, the polymers have much lower crystallinity and also lower nematic‐to‐isotropic transition temperatures. The significant depression in crystallinity can be attributed to flexible chain segments laterally attached to the oligo p‐phenylene rods, which prevent close packing of the rods and thus disrupt the crystallization. The destabilization of the liquid‐crystalline phase is due to the diluting effect of the flexible polymer backbones; that is, the concentration of the mesogenic groups is reduced. The polymer containing p‐pentaphenyl can still exhibit good solubility in common solvents and emit light at about 402 nm in the solvent tetrahydrofuran. In the solid state, the emission redshifts to 418 nm, which is fairly close to the blue‐light emission. An interdigitated packing structure of mesogenic groups has been proposed to represent the structure of the polymer in the oriented state. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3394–3402, 2005

A Liquid Crystalline Elastomer with a p‐Pentaphenyl Transverse Rod Laterally Attached to the Main Chain

“…[12] A similar packing structure to that in Figure 10 has been proposed previously by He [6] and earlier by Ringsdorf [1] for their nematic LC copolymers containing transverse rods capable of a maximum 608 rotation upon stretching. In these cases, in which there is no siloxane component to drive nanoscale segregation, a quiescent nematic arrangement that either has transverse rods and the polymer chain locally oriented in the same direction [6] or has transverse rods interdigitated at a large acute angle to the local polymer chain direction [1] is possible. In our case, with a regularly spaced siloxane unit driving lamellar organization, the arrangement in Figure 10 is possible.…”

“…There have been previous reports of laterally linked mesogens of high molar mass. [1][2][3][4][5][6][7] The meta linkage was chosen here because it could, in principle, produce a 908 angle between the pentaphenyl rod and the chain direction in the fully extended chain case.…”

Order and strain in main-chain smectic liquid-crystalline polymers and elastomers

“…The third and final system (denoted as TR5; from Atlanta) has a Sm-A phase below about 50 • C. For this material the long direction of the sample coincides with the layer normal. This material is rather peculiar because of the presence of transverse pentaphenyl rods [22]. To maintain the Sm-A symmetry the rods are expected to orient locally parallel to the smectic layer normal, similarly in laterally substituted low-molecular mass systems [23].…”

Inducing out‐of‐plane auxetic behavior in needle‐punched nonwovens

“…In addition to synthetic macromolecular approaches to produce a nanoscale material with intrinsic auxetic properties, there has been extensive effort to induce auxetic response via clever tailoring of processing conditions using conventional polymers. Following on to Lakes treatment of conventional open‐cell polymeric foams to produce a negative Poisson's ratio, process modification of linear polymers such as polyethylene was successful in achieving auxetic response.…”