Dimension Changes in a Chemomechanical Polymer Containing Ethylenediamine and Alkyl Functions as Selective Recognition Units

Schneider, Hans‐Jörg; Liu, Tianjun; Lomadze, Nino

doi:10.1002/ejoc.200500633

Cited by 19 publications

(48 citation statements)

References 58 publications

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“…The changes in the size of the gel particles (generally 0.8 0.8 0.4 mm; volume 0.26 mm 3 after swelling in water) were determined as described earlier [10] with the help of a measuring microscope connected to a digital camera with suitable software. The changes in the length and width were used to calculate the volume changes.…”

Section: Methodsmentioning

confidence: 99%

Direct Translation of Chiral Recognition into Mechanical Motion

Schneider

Katō

2007

Angew Chem Int Ed

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Chiral recognition is of fundamental importance in nature, and also for a manifold of chemical applications. Enantioselectivity is the landmark of many new synthetic strategies and the basis of separation techniques, for example, for drugs. In all these processes the recognition manifests itself in the predominant formation of one enantiomer, be it after the synthesis or after the separation. The direct translation of chiral recognition into mechanical motions has to the best of our knowledge never been reported. The influence of chiral effector compounds or constituents on gelation, on the structure of gel materials, [1] and on phase or sol-gel transitions [2] has received increasing attention. Until now, supramolecular reactions in chemomechanical polymers has been only known to be selective with respect to regioisomeric effector molecules.[3] We describe here how interaction of a chemomechanical hydrogel with chiral effector molecules in the aqueous surrounding can lead to a volume decrease of 95 %, whereas the optical isomer triggers a change of less than 20 %, depending on the effector concentration.We used chitosan as the hydrogel as it contains aminoglucose units as chiral centers, and has been used, for example, for the separation of enantiomers.[4] The gel contains about 47 % water after preswelling with water; the gels exhibit additional volume expansion if exposed to anionic effector molecules which can bind to the protonated chitosan amino groups. Preliminary tests showed with O,O'-dibenzoyltartaric acids (DBTA, 1 c) that significant differences between the optical isomers already exist, and become smaller with increasing pH value (see the Supporting Information). Dramatically increased effects could be observed with gels containing acetic acid as cofactors. Investigations with other chemomechanical polymers have already shown that the cooperative action of different effector compounds in a gel can lead to significant alterations and enlargements of the volume changes. [5] Treatment of chitosan first with 50 mm acetic acid yields a gel with higher water content (96 %). Exposure of this gel to a number of different anionic effectors then results in significant volume contraction instead expansion.[6] The volume differences of the resulting gels formed with l-or d-DBTA can amount to be almost a factor of ten, depending on the effector concentration (Figure 1). Noticeably, the d isomer triggers large motions at quite low concentrations, at which the l enantiomer is barely active. As expected, a racemic mixture ([d + l-DBTA] = 5 mm) leads to a slightly smaller effect (À93 %) than that of the d isomer (À95 %), as the l isomer binds to a lesser degree.At higher concentrations, in contrast, the l isomer has larger effects than the d enantiomer. The concentration profiles can be ascribed to a higher affinity of the d isomer, so that the l enantiomer is fully bound only at higher concentrations. The contraction is believed to be the result of ionic cross-linking by the two carboxylate groups of the DBTA, which...

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Section: Methodsmentioning

confidence: 99%

Direct Translation of Chiral Recognition into Mechanical Motion

Schneider

Katō

2007

Angew Chem Int Ed

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“…Analyte specificity and responsiveness can be achieved with molecular imprinting strategies [117,150,151]. Molecular imprinting was shown to improve selectivity for glucose in one sensor design [118,119] and selectivity to metal ions in another [152]. Watanabe et al [153] produced norephedrine- and adrenaline-imprinted stimuli-responsive gel with molecular recognition achieved by molecular imprinting.…”

Section: Overview Of Gel-based Materials By Applicationmentioning

confidence: 99%

Role of mechanical factors in applications of stimuli-responsive polymer gels – Status and prospects

Goponenko

Dzenis

2016

Polymer

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Due to their unique characteristics such as multifold change of volume in response to minute change in the environment, resemblance of soft biological tissues, ability to operate in wet environments, and chemical tailorability, stimuli responsive gels represent a versatile and very promising class of materials for sensors, muscle-type actuators, biomedical applications, and autonomous intelligent structures. Success of these materials in practical applications largely depends on their ability to fulfill application-specific mechanical requirements. This article provides an overview of recent application-driven development of covalent polymer gels with special emphasis on the relevant mechanical factors and properties. A short account of mechanisms of gel swelling and mechanical characteristics of importance to stimuli-responsive gels is presented. The review highlights major barriers for wider application of these materials and discusses latest advances and potential future directions toward overcoming these barriers, including interpenetrating networks, homogeneous networks, nanocomposites, and nanofilamentary gels.

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“…The water-swollen hydrogels already contain up to 98 % water before the addition of an effector: all reported effector-induced changes refer to this starting value. Figure 2 shows that indeed most of the observed volume change is due to additional water uptake, with only minor contributions from the effector molecules themselves 23. The importance of solvation changes in host-guest complexation has been stressed for many years; in chemomechanical polymers such changes can be quantified by gravimetry,23 and also by FT-IR measurements 24.…”

Section: Principles: Expansion and Contraction / Water Uptake And mentioning

confidence: 98%

Supramolecular Interactions in Chemomechanical Polymers

2009

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ConspectusMolecular recognition is the basis for the operation of most biological functions; outside of nature, it has also been developed to a high degree of sophistication within the framework of supramolecular chemistry. More recently, selective noncovalent interactions-which constitute molecular recognition-are being used in intelligent new materials that transform chemical signals into actions, such as the release of drugs. The presence of supramolecular binding sites allows chemomechanical polymers to operate as sensors and actuators within a single unit without the need for any additional devices such as transducers or power supplies.A polymer can be designed so that a particular chemical substance, most often in aqueous surroundings, will trigger either a large expansion or a large contraction, depending on the mechanism. The translation of binding energy into mechanical motion can, with a suitable arrangement of the materials in tubes or on flexible films, be harnessed for unidirectional drives, flow control, the liberation of drugs, or the uptake of toxic compounds, among other applications. Miniaturization of the polymer particles allows one to enhance both the sensitivity and speed of the response, which is of particular importance in sensing.The basis for the selective response to external effector compounds, such as metal ions, amino acids, peptides, or nucleotides, is their noncovalent interaction with complementary functions covalently bound to the polymer network. With suitable polymers, selectivity between structural isomers-and even between enantiomers-as triggers can be achieved. As with supramolecular complexes in solution, the underlying interactions in polymers comprise a variety of noncovalent binding mechanisms, which are not easy to distinguish and quantify-and more so with polymers, which are not monodisperse. In this Account, we present systematic comparisons of different polymers and effector classes that allow, for the first time, the characterization of these contributions in chemomechanical polymers: they comprise ion pairing, metal coordination, stacking, cation-π, dispersive, and hydrophobic forces. In contrast, hydrogen bonding has a major role primarily in the hydrogel network structure.The fully reversible polymer volume changes are essentially determined by water uptake or release. In gels derived from boronic acid, glucose can serve as a cross-linking effector in promoting contractions via strong, reversible covalent bond formation in a highly distinctive manner. Cooperativity between two different effector compounds is more frequently seen with such polymers than in solution: it leads to logical AND gates by different motions of the particles, with a direct communication link to the outside world. For example, with a polymer that bears several recognition sites, triggering peptides induce motion only if Zn 2+ or Cu 2+ ions are simultaneously present.The molecular recognition mechanisms that cause volume changes in polymers share similarities with extensively studied supram...

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Dimension Changes in a Chemomechanical Polymer Containing Ethylenediamine and Alkyl Functions as Selective Recognition Units

Cited by 19 publications

References 58 publications

Direct Translation of Chiral Recognition into Mechanical Motion

Direct Translation of Chiral Recognition into Mechanical Motion

Role of mechanical factors in applications of stimuli-responsive polymer gels – Status and prospects

Supramolecular Interactions in Chemomechanical Polymers

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