Meso‐Epitaxial Solution‐Growth of Self‐Organizing Discotic Liquid‐Crystalline Semiconductors

Abstract

Conjugated polymer actuators developed over the last decade have now reached the early stages of commercialization, particularly for use in biomedical devices, such as the blood vessel connector shown in the Figure. This article reviews the motivation for using this class of actuator, the types of devices that have been fabricated, and some of the biomedical applications that are being developed. Recommendations are also presented for future work. CommunicationsSubstituted hexabenzocoronenes (HBCs) form films with supramolecularly ordered columnar stacks that are uniaxially oriented onto poly(tetrafluoroethylene) alignment layers (see Figure). In field-effect transistor (FET) tests, mobilities of up to 10 ±3 cm 2 V ±1 s ±1and high on±off ratios of more than 10 4 were derived for these aligned HBC films, characteristics superior to FETs prepared from isotropic HBC layers.

Mesomorphic Hexabenzocoronenes Bearing Perfluorinated Chains

“…It is important to note that this particular organization of a product in the solid phase upon heating is reported for the first time for a HBC derivative and proves the high ability of these products to self-assemble in well-defined architectures. In contrast, the mesophase of HBC-Rf 6,6 is formed from a succession of various crystalline phases, and at a lower temperature than that of HBC-Rf 4,8 .…”

“…The very high viscosity of the perfluorinated HBC products did not permit, when analyzed under POM, the growth of characteristic optical textures, allowing for an accurate mesophase identification except for HBC-Rf 4,8 . Indeed, this compound revealed an interesting phenomenon: the yellowish amorphous powdered precipitate rapidly transforms to long needlelike crystalline structures on heating when reaching a temperature of ∼110°C (Figure 7).…”

“…It appears that an ethylene spacer does not fully isolate the electron-withdrawing effect of a perfluoroalkylated chain since the corresponding alkylated products were obtained in very good yields 6 even under the milder FeCl 3 /CH 3 -NO 2 conditions. 26 It must be pointed out, however, that both products HBC-Rf 2,8 and HBC-PhRf 2,8 display a very low solubility, which leaves MALDI-TOF as the only technique to detect the presence of the desired products (Figure 1) using the same special sample preparation method reported in the literature, 27 but employing the more efficient DCTB matrix. 28 In an attempt to decouple the perfluoroalkyl chains totally from the HBC core, we synthesized the HBC-Rf 4,8 (28) and HBCRf 6,6 (29) derivatives bearing perfluoroalkylated side chains with alkyl intercalators of four and six aliphatic carbons, respectively, in a scheme requiring fewer steps (Scheme 3).…”

“…4,5 Additionally, its solubility was improved by the addition of peripheral long aliphatic chains which at the same time bestows the molecule with a ditopic property: These HBC derivatives show a liquid crystalline (LC) state over a wide temperature range depending on the length of the aliphatic chain. 6 Moreover, these HBC derivatives exhibit the highest charge carrier mobility recorded so far for an organic molecule both in the solid and in the liquid crystalline states, 7 paving the way toward their application in the domain of electronic 8 and optoelectronic [9][10][11] devices.…”

π-Conjugated polymer-layered structures: synthesis and self-assembly

“…[3][4][5][6][7][8][9][10][11] Because π-conjugated compounds tend to aggregate by π-π stacking, the introduction of non-covalent interactions at appropriate positions increases their association constants and facilitates the formation of higher-ordered structures. 12,13 For example, supramolecular gels can be formed through intermolecular interactions such as hydrogen bonds, 14,15 and multiple long alkyl chains facilitate columnar stacking along the π-stacking direction of supramolecular assemblies [16][17][18][19] (Figure 1a). A variety of assembled structures can be formed through covalent linkages between π-conjugated units (Figure 1b).…”