Both the role of the absolute configuration and the tendency of a chiral monomer to promote a certain helical scaffold in a poly(phenylacetylene) (PPA) have been evaluated to study the communication between two chiral monomers within a copolymer chain. Nineteen different PPA copolymer series-47 helical copolymers altogether-were prepared to explore the existence of a chiral-to-chiral communication mechanism. From the data obtained, we found that communication between two different chiral monomers emerges when both exhibit two special features: (a) a different conformational composition-one must exist in a single low-energy conformation ("chiral Sergeant") and the other must present two conformers ("chiral Soldier")-and (b) the induction of a similar scaffold in the PPA, either cis-cisoidal or cis-transoidal. In the selected systems, the chiral Soldier includes the 4-ethynylanilide (para position) of either (R)- or (S)-2-methoxy-2-phenylacetic acid pendants characterized by their conformational flexibility (equilibrium between synperiplanar and antiperiplanar conformations). The chiral Sergeant contains the same chiral groups but linked to the backbone in meta position [3-ethynylanilide of (R)- or (S)-2-methoxy-2-phenylacetic acid] and is selected on the basis of its restricted antiperiplanar conformation. Incorporation of a very small amount (1%) of the Sergeant into a chain composed of just the Soldier transforms the originally axially racemic chain into a helix with strong sense preference (either M or P) that is determined by the absolute configuration of the Soldier.

Cation–π interactions determine the helical sense adopted by a polyphenylacetylene bearing (R)-α-methoxy-α-phenylacetamide as a pendant group (poly-1).

An ew multi-sensor material based on helical copolymers showing the chiral conflict effect have been prepared. It can successfully detect and identify diverse metal cations in solution. The design of this material has taken into account not only the opposite helical senses induced by the two chiral monomers in the copolymer,b ut also their dynamic behavior.T he induced helical sense can thus be enhanced, diminished, or inverted by interaction with different stimuli (that is,m etal ions). Thus,d epending on both the copolymer compositions (such as monomer ratios and absolute configurations) and the nature of the metal ion, the response of these dynamic helical copolymers to adopt as ingle-handed PorM helix is unique,m aking it possible not only to detect their presence,b ut also to identify them individually.N ew multisensors materials based and inspired on this effect should arise in the future choosing appropriate monomers and stimuli.The helical structures of dynamic polymers,s uch as poly-(phenylacetylene)s (PPAs), are usually stabilized by supramolecular interactions between monomer repeating units along the polymer chains,w ith steric effects also playing arole. [1][2][3][4][5][6][7][8][9][10] Controlled conformational changes at the pendant groups modulate these supramolecular and/or steric interactions, resulting in variations on the helical structure of the polymer, that is,e longation [11][12][13] and/or helical sense. [14,15] Thus,c hiral amplification, helical enhancement, or helix inversion can be induced by the action of appropriate external stimuli. [1][2][3][4][5][6][7][8][9][10] In the case of copolymers formed by the combination of chiral and achiral monomers,t he modulation of the helical structure may occur through ac onformational communication mechanism (going from the chiral to the achiral pendants) that originates ac hiral amplification phenomenon denoted as the sergeants and soldiers effect. [16][17][18][19][20][21][22][23][24][25][26][27][28] In such acase,the presence of asmall amount of the chiral monomer (minor component, sergeant) commands the secondary structure of the whole copolymer chain, that is,e ither M or P helices,b yi nducing ac ertain spatial orientation in the achiral units (major component, soldier). Recently,our group extended the concept of the sergeants and soldiers effect to am ore complex situation of PPAc opolymers;s pecifically, bipolymers,that is,c opolymers derived from two monomers, in which the two components are chiral. [16,17] In this way,one of them acts as ac hiral sergeant, while the other acts as ac hiral soldier.H ence,w hile the helical sense of the copolymer (that is,i ts M or P helicity) is commanded by the absolute configuration of the sergeant (minor component), the chirality at the periphery of the helix depends on the intrinsic chirality of the soldier (major component).Those studies showed that this chiral-to-chiral communication phenomenon, which is operative along ac opolymer chain and responsible of the enhancement of asingle-handed helicity,w...

The interaction of a highly dynamic poly(aryl acetylene) (poly-1) with Li(+), Na(+), and Ag(+) leads to macroscopically chiral supramolecular nanospheres, nanotubes, toroids, and gels. With Ag(+), nanospheres with M helicity and tunable sizes are generated, which complement those obtained from the same polymer with divalent cations. With Li(+) or Na(+), poly-1 yields chiral nanotubes, gels, or toroids with encapsulating properties and M helicity. Right-handed supramolecular structures can be obtained by using the enantiomeric polymer. The interaction of poly-1 with Na(+) produces nanostructures whose helicity is highly dependent on the solvation state of the cation. Therefore, structures with either of the two helicities can be prepared from the same polymer by manipulation of the cosolvent. Such chiral nanotubes, toroids, and gels have previously not been obtained from helical polymer-metal complexes. Chiral nanospheres made of poly(aryl acetylene) that were previously assembled with metal(II) species can now be obtained with metal(I) species.