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...
A precise tuning of the four possible states of a helix (P/M helical sense and stretched/compressed helical backbone) is attained by controlling the complexation between Li and a poly(phenylacetylene) that bears amide, ester and phenyl ring functionalities at the pendant group. Depending on the MeOH ratio that is present as a cosolvent, different coordination sites are involved in interactions leading to complexes I-III, each one with a characteristic structure (tri-, bi-, and unipodal) and an associated helical state. This dynamic coordination allows the selective modification of the helical sense or the stretching/compression backbone of a helical polymer.
A new 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, but also their dynamic behavior. The induced helical sense can thus be enhanced, diminished, or inverted by interaction with different stimuli (that is, metal ions). Thus, depending 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 a single‐handed P or M helix is unique, making it possible not only to detect their presence, but also to identify them individually. New multi‐sensors materials based and inspired on this effect should arise in the future choosing appropriate monomers and stimuli.
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