Hierarchically Controlled Helical Graphite Films Prepared from Iodine-Doped Helical Polyacetylene Films Using Morphology-Retaining Carbonization

Abstract

One-handed helical graphite films with a hierarchically controlled morphology were prepared from iodine-doped helical polyacetylene (H-PA) films using the recently developed morphology-retaining carbonization method. Results from scanning electron microscopy indicate that the hierarchical helical morphology of the H-PA film remains unchanged even after carbonization at 800 °C. The weight loss of the film due to carbonization was very small; only 10-29% of the weight of the film before doping was lost. Furthermore, the graphite film prepared by subsequent heating at 2600 °C retained the same morphology as that of the original H-PA film and that of the helical carbon film prepared at 800 °C. The screwed direction, twisted degree, and vertical or horizontal alignment of the helical graphite film were well controlled by changing the helical sense, helical pitch, and orientation state of the chiral nematic liquid crystal (N*-LC) used as an asymmetric LC reaction field. X-ray diffraction and Raman scattering measurements showed that graphitic crystallization proceeds in the carbon film during heat treatment at 2600 °C. Transmission electron microscopy measurements indicate that ultrasonication of the helical graphite film in ethanol for several hours gives rise to a single helical graphite fibril. The profound potentiality of the present graphite films is exemplified in their electrical properties. The horizontally aligned helical graphite film exhibits an enhancement in electrical conductivity and an evolution of electrical anisotropy in which conductivity parallel to the helical axis of the fibril bundle is higher than that perpendicular to the axis.

Molecular iodine/polymer complexes

“…The doped DPVC showed electrical conductivity in the range of 1.2 × 10 3 S·cm 1 to 2.1 × 10 1 S·cm 1 . Goh et al [273], Kyotani et al [296], and Matsushita et al [297,298] invented a way to make helical polyacety lene and helical carbon and graphite films thereof. Helical polyacetylene (HPAC) was obtained by polymerizing acetylene using the ZieglerNatta catalyst, Ti(OnBu) 4 AlEt 3 , dissolved in an asymmetric nematic liquid crystal (NLC) composed of a mixture of (S)1,1′binaphthyl 2,2′di[p(trans4npentylcyclohexyl)phenoxy1hexyl] ether, p(trans4npropylcyclohexyl)ethoxybenzene, and p(trans4npropylcyclohexyl)butoxybenzene.…”

Supramolecular Chirality: Solvent Chirality Transfer in Molecular Chemistry and Polymer Chemistry

“…Since 1998, Akagi et al have developed the chiral nematic liquid crystal field with the induced polymerization of various polymerizable monomers involving acetylene gas with the help of catalytic and electrochemical polymerization reactions (Figures 29-31) [77,[148][149][150][151][152][153]. The helical shapes of polymers during polymerization are retained, because the resulting polymers are insoluble in these chiral liquid crystals.…”

Helical Nanostructure of Achiral Silver p-Tolylacetylide Molecules

“…Recent development in nanotechnology has produced helical species on the nanoscale. The aggregation of molecules can form nano-helical structures in supramolecular chemistry [1][2][3][4][5]. Helices coiled in the right-handed or left-handed direction can be formed, depending on the chirality of the constituent molecules.…”