Abstract
The design, synthesis and structure elucidation of helical polymers with a predominant helical sense have been actively studied during the last years due to the different applications that these materials can present. The helical sense of a polymer can be determined by the chirality of the pendants and is directly related to the distance from the chiral centre to the backbone. In order to achieve the best folding this distance between the polymeric backbone and the chiral centre should be small, so the closer is the pendant to the backbone the better is the helical control. Nevertheless, few examples have demonstrated that the helical control is also possible when a spacer is placed between the pendant and the backbone. Related to this, our research group has proved that is possible to have chiral teleinduction when the chiral centre is separated form the backbone through a flexible spacer. Recently, we have also demonstrated that the transmission of information is also possible when a long rigid and achiral spacer is employed observing that, although the chiral centre is placed in a remote position, its chirality is transmitted to the polyene backbone through a previous organization into a helical fashion of the rigid spacer. Herein we describe another family of polymers bearing an achiral rigid spacer between the pendant and the backbone, evaluating the effect that the aromatic substitution pattern of the rigid spacer has over the final folding of the polymer.
Highlights
Dynamic helical polymers have emerged as an attractive field due to the possibility of tuning the helical sense and/or the elongation of the helical structure
In the case of chiral dynamic helical polymers, a conformational change is produced in the chiral moiety, whereas in the case of achiral polymers the modulation of the pendant is produced by the addition of a chiral molecule
Some examples have demonstrated that the transmission of chiral information from a remote position can occur at long distances through space, overcoming the distance generated by the spacer—teleinduction [2]—or by the achiral spacer itself— conformational switch [3]—We have recently reported for the first time a novel mechanism for the transmission of chiral information in helical polymers derived from poly(phenylacetylene)s (PPAs)
Summary
Dynamic helical polymers have emerged as an attractive field due to the possibility of tuning the helical sense and/or the elongation of the helical structure. 2020, 1, FOR PEER REVIEW bearing an oligo(p-phenyleneethynylene) (OPE) spacer between the pendant and the backbone [4] In this new family of polymers—poly(p-oligophenyleneethynylene)s (POPEPAs)—the helical induction is produced by a combination of chiral teleinduction together with a chiral harvesting process—the chiral information is transmitted to the achiral spacer resulting into a stacking of the OPE units, which is further harvested by the polyene backbone— and is effective for a distance of 2.4 nm. This helix induction was observed to occur despite modifying the aromatic substitution pattern. Taking into account these remarkable results, we decided to evaluate the effect that the introduction of a meta- substituted OPE spacer [oligo(m-phenyleneethynylene)] will have over the folding of the helical structure
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