Cooperativity in the Folding of Helicalm-Phenylene Ethynylene Oligomers Based upon the `Sergeants-and-Soldiers' Principle

Abstract

The 'Sergeants-and-Soldiers' principle has been examined in a series of m-phenylene ethynylene oligomers containing both chiral and achiral side chains. Circular dichroism (CD) spectroscopy was used to examine the twist sense bias of the helical conformation in the polar solvent acetonitrile. A non-linear dependence of the CD signal on the amount of chiral side chains was observed revealing cooperative interactions among the side chains through the backbone. On the other hand, the experiments indicate that in acetonitrile a full bias of the helicity cannot be accomplished by chiral side chains alone. Nevertheless, the folded oligomers are highly ordered since the placement of a single chiral side chain at the beginning of an oligomer results in the induction of a strong twist sense bias into the ordered helical conformation.

Particles of polyacetylene and its derivatives: preparation and applications

“…130 nm, while in the case of microemulsion polymerization, the polymer particles were about 25 nm in diameter. Following the versatile strategies established by Mecking et al, more polymer particles can be expected from 75 acetylene and the derivatives. The studies from Mecking group also open new opportunities for practical applications of polymer emulsions derived from acetylenics, since the aforementioned disadvantages of polyacetylene and the derivatives can be, at least to some degree, circumvented by directly using and processing 80 polymer emulsions.…”

“…(2) In applications: The practices dealing with aqueous and nonaqueous acetylenic polymer particles shall provide advanced materials and feasible processing routes for polyacetylenes. They are also beneficial for 75 overcoming the disadvantages of polyacetylenes mentioned above.…”

Poly(aryleneethynylene)s

“…Solvophobic interactions drive helix formation, leading to a dynamic structure in which stability is controlled by solvent composition, temperature, oligomer length, and secondary interactions [30, [34][35][36][37]. Further, the chirality of the helix can be controlled by chiral side chains [38,39] or wrapping around chiral guest molecules [40][41][42]. Moore investigated the well-defined core of the foldamer as a ''reactive sieve'' [43], similar to the amino acid sieving mechanism of tRNA synthetase enzyme [44,45], where the reactivity of substrates is differentiated through size discrimination.…”

Self‐assembly of supramolecular polymers into tunable helical structures

“…[46][47][48][49][50][51][52] An example includes the amphiphilic meta-linked oligo (m-phenylene ethylene)s (OPEs) that can self-assemble into a helical conformation by combination of solvophobic effect and p-p interactions. 47 The formations of these helical conformations were confirmed by several spectroscopic techniques, including UV-vis absorption, fluorescence, and CD spectroscopies.…”