Chiral Cooperativity in Helical Polymers

Abstract

Human experience informs us of the two extreme consequences of crowding: random behavior of the individuals, in which each takes a singular path; and cooperative behavior, in which the individuals in the crowd act in a predictable uniform manner, such as in a military organization These extremes find parallels in the crowded situations encountered at the molecular level, exemplified for the former by glassy states, such as often encountered in polymeric materials,1 or for the latter, in the uniform archetypal arrangements of crystals or liquid crystals. Here we review the cooperative characteristics of uniform arrangements that take a chiral form and explore how these characteristics lead to left‐ and right‐handedness. These studies lead us to understand the basis of amplification of chirality in regular arrays, in which small influences have large consequences, and how chiral cooperativity acts in the resolution of conflict between influences favoring left‐ and right‐handedness.2

The First Suspension Polymerization for Preparing Optically Active Microparticles Purely Constructed from Chirally Helical Substituted Polyacetylenes

“…Optically active particles, as a newly emerging type of functional materials, elegantly combine in one entity the interesting properties of chiral polymers and the advantages of particulate materials such as a large specific surface area relative to the corresponding bulk material. In particular, particles consisting of chirally helical polymers, which often show the well‐known “chiral amplification” effects, are expected to exhibit remarkable optical activity.…”

Helix control in polymers

“…In such chains the helical sense excess, as measured by the CD intensity, should track with chain length, that is, with degree of polymerization. As the chain length increases, the helical reversal energy allows the possibility of reversals and the CD intensity should level off and become independent of degree of polymerization, but should decrease greatly with increasing temperatures 24 , 25 . These expectations are precisely observed, and in combination with theoretical calculations 24 have led to determination of the helical reversal energy in the range of 4,000 cal/mole, which at ambient temperature corresponds to one reversal approximately every 800 units along the chain.…”

Optically active helical polymers with pendent thiourea groups: Chiral organocatalyst for asymmetric michael addition reaction

“…Owing to their unique helical structures, these biomacromolecules play extremely significant roles in living organisms. Stimulated by natural helical macromolecules, so far various artificial polymers with chiral helical structures have been successfully designed and prepared . These helical polymers demonstrated fascinating features and found applications in enantioselective crystallization, chiral recognition, and so forth.…”