Preparation of Ordered Polyacetylene by Solid-State Polymerization in Nanoscale Confinement

Abstract

We report a novel, highly effective strategy for controlling the synthesis of polyacetylene as a guest in an organic host crystal by monitoring in situ an elimination−condensation polymerization reaction. Specifically, in this process, the polymer material is forced to have its chains extended and aligned such that translational periodicity applies, producing a bond alternation potential that has a symmetric double minimum. The synthetic approach used is photochemical elimination of iodine from a conjugated diene, (E,E)-1,4-diiodo-1,3-butadiene, which forms a commensurate and fully ordered urea inclusion compound. Photochemical cleavage of the terminal C−I bonds results in elimination of iodine from the single crystal and formation of C−C bonds between adjacent radicals to produce the conjugated 1,8-diiodo-1,3,5,7-octatetraene and subsequent longer polyene species. The combination of in situ crystal mass-loss measurements and vibrational Raman spectroscopy demonstrates clearly the presence of new polyene chains and loss of iodine from the urea substructure. The first few product oligopolyenes exhibit very strong Raman scattering with the most intense vibrational features decreasing in frequency for longer chains approaching an asymptotic limiting frequency that mimics the behavior of conjugated polyenes of known lengths from previous vibrational Raman studies. With extensive irradiation, the mass loss approaches that anticipated from the crystal stoichiometry and, at the same time of irradiation, the Raman intensity largely disappears. These results demonstrate that the reaction reported here proceeds to completion, leading to a quasi-one-dimensional array of isolated polyacetylene chains that are constrained to be in a continuous extended, all-trans conformation within the tunnels formed by the urea crystal lattice.

Stable solar water splitting with wettable organic-layer-protected silicon photocathodes

“…Quantitative in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) and Raman spectroscopy did not show any evidence of conductive functional groups 50 or conductive materials 51 formed in Si/TMOS at elevated temperature (Fig. S21 ).…”

Laser-induced ultrafast spin-transfer processes in non-linear zigzag carbon chain systems

“…[83][84][85] Notice that those systems are cut out of a graphene sheet, with hydrogen atoms saturating the bonds wherever necessary. Our systems belong to the polyacetylene chains [86][87][88][89][90][91][92][93][94][95] and carbon systems groups. [96][97][98][99][100] The idea of employing polyacetylene chains to connect the magnetic centers over large distances stems from cutting stripes out of graphene sheets.…”

Acetylenedicarboxylate as a linker in the engineering of coordination polymers and metal–organic frameworks: challenges and potential

“…143,144 The polymerization in the solid-state is favored, when the unsaturated moieties in the respective material are correctly oriented to each other with short contacts between them (< 4.2 Å). 145 Molecules with C-C triple bonds are especially interesting for SSP, as they would yield the formation of π-conjugated polymers, which can result in materials with interesting electrical and non-linear optical properties. 146 However, the SSP of "all-organic" acetylenes is usually very limited.…”