Induced chiral helical effect on the main chain of aliphatic polyacetylenes

Abstract

11‐Dodecyn‐1‐ol as an achiral, aliphatic, monosubstituted acetylene was copolymerized with cholesteryl 3‐butynyl carbonate as a chiral, aliphatic, monosubstituted acetylene with Rh(nbd)[B(C6H5)4] (nbd = norbornadiene) in tetrahydrofuran. The main chain of the obtained copolymers seemed to be mainly composed of the cis‐type structure. The backbone π–π* transition of these copolymers showed significant circular dichroism (CD), indicating an excess of one‐handed helical conformation. These CD signals were varied with the contents of the cholesteryl units in the copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 913–917, 2001

Helical Conjugated Polymers: Synthesis, Stability, and Chiroptical Properties of Poly(alkyl phenylpropiolate)s Bearing Stereogenic Pendants

“…It is, however, noteworthy that, though the magnitudes of the [α] 20 D 's of the polymers vary with solvent, their signs (+ or −) remain unchanged. This is in contrast to what observed in the helical monosubstituted polyacetylene systems, where not only the magnitudes of their [α] 20 D 's change vigorously but also their signs reverse with a change in solvent. − For example, the [α] 20 D values of a poly(phenylacetylene) bearing l-alanine pendants are +440.0° and −953.2° in THF and chloroform, respectively (noting the sign inversion) . A disubstituted polyacetylene chain is generally more rigid than a monosubstituted one, and it is believed that the chain stiffness of P 1 −P 4 has helped keep their helical-sense preference unaltered by the solvent perturbation.…”

“…Attachments of appropriate pendants to the polyacetylene backbone can not only help improve the processability and stability but also generate new polyacetylene derivatives with functional properties that are absent in the parent form. , An example in this regard is the incorporation of stereogenic groups into polyacetylene chains. Enthusiastic synthetic effort in the area has resulted in the creation of a large variety of helical substituted polyacetylenes, most of which are soluble, some of which are stable, and all of which are optically active, although the optical activity varies considerably from one polymer to another. − …”

“…Most of the optically active polyacetylenes bear one substituent in each of their monomer repeat units (and are hence monosubstituted ), with an overwhelming majority of them being poly(phenylacetylene) and polypropargyl derivatives. − While the monosubstituted polyacetylenes are more stable than their unsubstituted polyacetylene parent, their stabilities are still of concern for many practical applications. , One way to further enhance the polymer stability is to add one more substituent into the repeat unit to make a disubstituted polyacetylene, which is generally more stable than its monosubstituted homologue. 3a, For example, poly(1-chloro-2-phenylacetylene), an achiral disubstituted polyacetylene, does not degrade when heated in air at 120 °C for 20 h, whereas poly(phenylacetylene) readily decomposes when treated under the same conditions …”

Helix Inversion of Polyaniline by Introducing o-Toluidine Units

“…Copolymerization greatly increases the ability of the polymer scientists to tailor-make a material with specifically desired properties. In addition, copolymerization of enantiopure chiral monomers with achiral monomers or with an enantiomeric excess (ee) of one enantiomer over the other was reported as an effective route to obtain polymers with a preferential screw-sense main chain . It is the presence of the enantiopure chiral “seeds” which results in the adoption of a preferential helical screw sense in even non-enantiopure-substituted backbone regions by the preferential stereorelationship between enantiopure chiral side chains and their nearest neighbors.…”

Synthesis and characterization of novel crosslinkable polymers with a nonlinear optical chromophore as a pendant group

“…However, polyacetylene has not been fully investigated because of its low solubility, processability, and thermal stability. To circumvent these problems, several methods have been developed, mostly based on the introduction of substituents into the polymer main chain;13, 14 this improves solubility in common organic solvents and air and thermal stability. The direct synthesis of poly(arylene vinylene) derivatives with all trans ‐vinylene bonds has been accomplished via acyclic diene metathesis with 1,4‐divinylbenzene.…”