Memory Of Macromolecular Helicity Research Articles

Thermally stable and rewritable circularly polarized luminescent helical poly(diphenylacetylene)s: stabilization of macromolecular helicity memoryviareversible ion-pair formation

An enhancement of stability of helicity memory, solubility, and fluorescence properties of a poly(diphenylacetylene) has been achieved through ion-pair formation.

Helical Polymers with Dynamic and Static Macromolecular Helicity Memory: The Power of Helicity Memory for Helical Polymer Synthesis and Applications

Abstract In this Account, we describe the recent progress in the synthesis and unique features and functions of helical polymers with a controlled handedness based on the noncovalent helicity induction and subsequent memory of the helicity strategy that we have developed during the past two decades. Remarkable progress has been achieved in the emerging research area of helical polymers over the past decades, producing a number of helical polymers with various structures and functions. Nevertheless, the helical polymers with dynamic and static helicity memory have been proved to be exceptional and like no other among a huge number of helical polymers prepared so far because of their unique and exclusively outstanding features, such that an excess handed helicity, once induced by noncovalent weak chiral interactions, is immediately memorized accompanied by a significant amplification of the helical chirality, leading to a long-lasting helicity memory. This finding has a significant impact on the development of novel advanced chiral materials, such as switchable chiral stationary phases for separating enantiomers and asymmetric catalysts, which will also be described in this Account.

Catalytic one-handed helix-induction and memory of amphiphilic poly(biphenylylacetylene)s in water

A series of amphiphilic biphenylylacetylene-based homo- and copolymers (PBPAs) carrying chiral and/or achiral oligo(ethylene glycol) pendants at the 4′-position of the biphenyl units were synthesized and the amplification of the macromolecular helicity through noncovalent and/or covalent chiral interactions followed by the memory of the helicity were investigated in both water and organic solvents. The macromolecular helicity was efficiently induced in the homopolymers of achiral monomers through specific encapsulation of a catalytic amount of hydrophobic chiral guests in water and their induced helicities were stably memorized in water after complete removal of the optically-active guests, while an excess helical sense was not biased at all in the homopolymers in toluene. One-handed macromolecular helicities were also efficiently induced in the chiral homopolymers through chiral information transfer from covalently linked optically-active pendants with a point chirality to biphenyl units with a dynamic axial chirality, whose helical senses were almost perfectly inverted in water and organic solvents. The achiral/chiral copolymers displayed a unique bidirectional (P and M) strong chiral amplification of the macromolecular helicity in water and toluene assisted by the solvent-induced helix-inversion, and their macromolecular helicities were further enhanced or inverted through encapsulation of a catalytic amount of enantiomeric alcohols in water, which could be further memorized in water after removing the encapsulated guests. We also demonstrated that the left- and right-handed circularly polarized lights could be generated through chirality transfer from the one-handed helical polymers with a macromolecular helicity memory, consisting entirely of achiral monomer units, to an achiral fluorescent dye in the blended films. Importantly, the resulting luminescence dissymmetry factors (ca. 2 × 10–3) were virtually the same as those of chiral homopolymers composed of the optically-pure repeating units.

Helicity Induction and Its Static Memory of Poly(biphenylylacetylene)s Bearing Pyridine N‐Oxide Groups and Their Use as Asymmetric Organocatalysts

ABSTRACTNovel poly(biphenylylacetylene) derivatives carrying different types of pyridine N‐oxide units with a bulky or less‐bulky substituent at a different position as the functional pendant groups (poly‐2a and poly‐2b) were synthesized by the rhodium‐catalyzed polymerization of the corresponding monomers. The influence of the steric environment around the catalytically active pyridine N‐oxide sites on the helicity induction and its static memory as well as the asymmetric catalytic activities of the resulting helical polymers with a macromolecular helicity memory was investigated. The polyacetylenes formed an excess one‐handed helical conformation upon noncovalent interactions with optically active alcohols and the induced macromolecular helicities of the polyacetylenes were efficiently memorized after the removal of the chiral inducers. Poly‐2b with the macromolecular helicity memory showed an enantioselectivity for the catalytic asymmetric allylation of benzaldehydes, producing optically active allyl alcohols, although their enantioselectivities were low. On the other hand, poly‐2a exhibited a negligible catalytic activity probably due to the bulky substituent at the o‐position of the pyridine N‐oxide residues, while poly‐2a underwent a unique helix‐inversion with the increasing concentration of chiral alcohols and the opposite helicity of poly‐2a was further successfully memorized. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2481–2490

Macromolecular Helicity Induction and Memory in a Poly(biphenylylacetylene) Bearing an Ester Group and Its Application to a Chiral Stationary Phase for High-performance Liquid Chromatography

Abstract An optically inactive poly(biphenylylacetylene) bearing an ester group at the 4′-position of the pendants formed a preferred-handed helical conformation and biased axial chirality in the pendants through a noncovalent interaction with a chiral alcohol, both of which were retained (memorized) even after removal of the chiral alcohol. The chiral stationary phase for high-performance liquid chromatography, prepared by coating the polymer with macromolecular helicity memory on silica gel, showed good chiral recognition ability towards various racemates.

Enantioseparation on poly(phenyl isocyanide)s with macromolecular helicity memory as chiral stationary phases for HPLC

A series of novel optically active poly(phenyl isocyanide)s bearing achiral benzanilide pendant groups was prepared based on the noncovalent “helicity induction and memory strategy”. The polymers that exhibited an optical activity due to the macromolecular helicity memory were immobilized to 3-aminopropyl-silanized silica gel through chemical bonding or coated on the silica gel to obtain chiral packing materials for high-performance liquid chromatography (HPLC). The chiral recognition abilities toward a variety of racemic compounds with different functionalities were investigated by HPLC. The obtained CSPs separated various racemates into enantiomers, in particular, a right-handed helical poly(phenyl isocyanide) carrying achiral anilide pendants showed an excellent chiral recognition ability and completely or partially resolved nine racemates, including cyclic ether, amine, ketones and metal acetylacetonate complexes, among twelve racemates.

Helix-Sense-Controlled Synthesis of Optically Active Poly(methyl methacrylate) Stereocomplexes

Optically active poly(methyl methacrylate) (PMMA) stereocomplexes were prepared through the helix-sense-controlled supramolecular inclusion of an isotactic (it) PMMA within the helical cavity of an optically active, fullerene-encapsulated syndiotactic (st) PMMA with a macromolecular helicity memory. The observed and calculated vibrational circular dichroism spectra revealed that the it-PMMA replaced the encapsulated fullerenes to fold into a double-stranded helix with the same handedness as that of the st-PMMA single helix through the formation of a topological triple-stranded helix.

Synthesis of functional poly(phenyl isocyanide)s with macromolecular helicity memory and their use as asymmetric organocatalysts

To develop a novel polymer-based asymmetric organocatalyst, a series of helical poly(phenyl isocyanide)s with functional pendant groups were prepared by modifying the side groups of the optically active helical poly(4-carboxyphenyl isocyanide) with a macromolecular helicity memory. Helical polyisocyanides partially modified with achiral amines, such as piperazine, maintained their chiral memory and enantioselectively catalyzed a direct aldol reaction. Although the enantioselectivity was low, the original helical poly(4-carboxyphenyl isocyanide) showed no catalytic activity. These results indicated that the macromolecular helicity of the modified polyisocyanides together with bifunctional amino and carboxy acid pendant residues arranged in a helical array along the polymer backbones plays an important role in the enantioselectivity.

Encapsulation of Fullerenes in a Helical PMMA Cavity Leading to a Robust Processable Complex with a Macromolecular Helicity Memory

Ein Gebrauchskunststoff – syndiotaktisches Poly(methylmethacrylat) (st-PMMA) – bildet in Gegenwart von (R)- oder (S)-1-Phenylethanol (1) rechts- bzw. linksgängige Helices, die Fullerene einschließen können. Dadurch entstehen beständige, optisch aktive Komplexe, die ihre Helizität auch nach Entfernen des chiralen Alkohols beibehalten (siehe Schema, rechts). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2008/z703655_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Encapsulation of Fullerenes in a Helical PMMA Cavity Leading to a Robust Processable Complex with a Macromolecular Helicity Memory

Encapsulation of Fullerenes in a Helical PMMA Cavity Leading to a Robust Processable Complex with a Macromolecular Helicity Memory

Unexpected Thermally Stable, Cholesteric Liquid‐Crystalline Helical Polyisocyanides with Memory of Macromolecular Helicity

The achiral sodium salt of poly(4-carboxyphenyl isocyanide) (poly-1-Na) folds into a one-handed helix induced by optically active amines in water. The induced helicity remains when the optically active amines are completely removed, and further modification of the side groups to amide residues is possible without loss of memory of macromolecular helicity. Although the helical poly-1-Na loses its chiral memory at high temperature, helical polyisocyanides modified with achiral primary amines, which no longer have any chiral components, keep their memory perfectly even at 100 degrees C in N,N-dimethylformamide in some cases and exhibit cholesteric liquid-crystalline phases, thus providing a robust scaffold with heat resistance to which a variety of functional groups can be introduced.

Cover Picture: Unexpected Thermally Stable, Cholesteric Liquid‐Crystalline Helical Polyisocyanides with Memory of Macromolecular Helicity (Chem. Asian J. 6/2007)

A good memory for macromolecular helicity is displayed by the one‐handed helical sodium salt of poly(4‐carboxyphenyl isocyanide) after the complete removal of the optically active amines that induced the helicity. This memory persists even with further modification to the side groups of the amide residues, thus giving designer helical polyisocyanides with outstanding thermal stability in solution, some of which also exhibit liquid crystallinity. To find out more, turn to the Full Paper by E. Yashima et al. on page 755 ff.

Enantioselective Esterification of Prochiral Phosphonate Pendants of a Polyphenylacetylene Assisted by Macromolecular Helicity: Storage of a Dynamic Macromolecular Helicity Memory

A poly(phenylacetylene) bearing a phosphonic acid monoethyl ester as the pendant forms a one-handed helical structure induced by an optically active amine, and this helicity can be "memorized"after the amine is replaced by achiral diamines. The helicity memory lasts for an extremely long time but spontaneously disappears after the achiral diamines are removed by a stronger acid, indicating the dynamic nature of the helicity memory. Here we report that such a dynamic memory could be "stored" after the pendant was converted to its methyl ester with diazomethane, resulting in the generation of a phosphorus stereogenic center with optical activity. The esterification enantioselectively proceeded through chirality transfer from the induced helical conformation or the helicity memory of the polyacetylene backbone. Although the enantioselectivity was low, the pendant chirality was significantly amplified in the polymer backbone at low temperatures, resulting in higher optical activity as an excess single-handed helix than that expected from the enantiomeric excess of the pendants.

Layer-by-layer assembly of charged poly(phenylacetylene)s with induced macromolecular helicity

The macromolecular helicity of charged poly(phenylacetylene)s induced by small chiral guests in water can be retained by the alternative deposition of achiral polyelectrolytes with opposite charges, resulting in optically active multilayer thin films with a macromolecular helicity memory.

An Optically Active Hydrogel Composed of Cross-linked Poly(4-carboxyphenyl isocyanide) with a Macromolecular Helicity Memory

Abstract Hydrogels composed of a poly(phenyl isocyanide) bearing a carboxylate group with a macromolecular helicity memory were synthesized by cross-linking with achiral diamines in water, and the obtained hydrogels were found to maintain their memory even at 90 °C in water, although the helical polymer before the cross-linking lost its memory at high temperature.

Mechanism of helix induction on a stereoregular Poly((4-carboxyphenyl)acetylene) with chiral amines and memory of the macromolecular helicity assisted by interaction with achiral amines.

Cis-transoidal poly((4-carboxyphenyl)acetylene) (poly-1) is an optically inactive polymer but forms an induced one-handed helical structure upon complexation with optically active amines such as (R)-(1-(1-naphthyl)ethyl)amine ((R)-2) in DMSO. The complexes show a characteristic induced circular dichroism (ICD) in the UV-visible region of the polymer backbone. Moreover, the macromolecular helicity of poly-1 induced by (R)-2 can be "memorized" even after complete replacement of (R)-2 by various achiral amines. We now report fully detailed studies on the mechanism of the helicity induction and memory of the helical chirality of poly-1 by means of UV-visible, CD, and infrared spectroscopies. We have found that a one-handed helix is cooperatively induced on poly-1 upon the ion pair formation of the carboxy groups of poly-1 with optically active amines and that the bulkiness of the chiral amines plays a crucial role for inducing an excess of a single-handed helix. On the other hand, the free ion formation was found to be essential for the macromolecular helicity memory of poly-1 after the replacement of the chiral amine by achiral amines, since the intramolecular electrostatic repulsion between the neighboring carboxylate ions of poly-1 significantly contributes to reduce the atropisomerization process of poly-1. On the basis of the mechanism of helicity induction and the memory of the helical chirality drawn from the present studies, we succeeded in creating an almost perfect memory of the induced macromolecular helicity of poly-1 with (R)-2 by using 2-aminoethanol as an achiral chaperoning molecule to assist in maintaining the memory of helical chirality.

An unprecedented memory of macromolecular helicity induced in an achiral polyisocyanide in water.

We have found an unprecedented memory of macromolecular helicity induced in an achiral sodium salt of poly(4-carboxyphenyl isocyanide) (poly-1-Na). Poly-1-Na folds into a one-handed helix through configurational isomerization around the C=N backbones by interactions with optically active amines in water. The helix remains when the optically active amines are completely removed, and further modifications of the side group to carboxy and esters can be possible without loss of the macromolecular helicity memory.

Memory of macromolecular helicity assisted by interaction with achiral small molecules

The helicity of biological macromolecules such as DNA and proteins is largely governed by the homochirality of their components (D-sugars and L-amino acids). In polymer and supramolecular chemistry, control of helicity is an attractive goal because of possible applications in materials science, chemical sensing and enantioselective catalysis1,2,3,4,5,6,7,8,9,10,11,12,13. We reported recently that macromolecular helicity can be induced in a polymer by an optically active amine14. Here we show that this helicity can be ‘memorized’ when the amine is replaced by various achiral amines. Although the maintenance of helicity in the polymer is not perfect, it can ‘repair’ itself over time. Small structural changes in the achiral amines influence the efficiency of helicity retention markedly.