Hierarchische Ordnung bei flüssigkristallinen Polykapseln

Castellano, Ronald K.; Nuckolls, Colin; Eichhorn, S. Holger; Wood, Malcolm R.; Lovinger, Andrew J.; Rebek, Julius

doi:10.1002/(sici)1521-3757(19990903)111:17<2764::aid-ange2764>3.0.co;2-0

Cited by 27 publications

(16 citation statements)

References 46 publications

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“…In these systems the addition of guest molecules induces the formation of polymer strands, while the H‐bonded capsules serve as connector units. Recently, it was also shown that mesogeneity can be induced by incorporating long aliphatic chains 442…”

Section: Properties and Applications Of H‐bonded Assembliesmentioning

confidence: 99%

Noncovalent Synthesis Using Hydrogen Bonding

Prins

Reinhoudt

Timmerman

2001

Angew. Chem. Int. Ed.

1,252

765

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Hydrogen bonds are like human beings in the sense that they exhibit typical grouplike behavior. As an individual they are feeble, easy to break, and sometimes hard to detect. However, when acting together they become much stronger and lean on each other. This phenomenon, which in scientific terms is called cooperativity, is based on the fact that “1+1 is more than 2”. By using this principle, chemists have developed a wide variety of chemically stable structures that are based on the reversible formation of multiple hydrogen bonds. More than 20 years of fundamental studies on these phenomena have gradually developed into a new discipline within the field of organic synthesis, and is nowadays called “noncovalent synthesis”. This review describes noncovalent synthesis based on the reversible formation of multiple hydrogen bonds. Starting with a thorough description of what the “hydrogen bond” really is, it guides the reader through a variety of bimolecular and higher order assemblies and exemplifies the general principles that determine their stability. Special focus is given to reversible capsules based on hydrogen‐bonding interactions that exhibit interesting encapsulation phenomena. Furthermore, the role of hydrogen‐bond formation in self‐replicating processes is actively discussed, and finally the review briefly summarizes the development of novel materials (nanotubes, liquid crystals, polymers, etc.) and principles (dynamic libraries) that recently have emanated from this intriguing field of research.

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Section: Properties and Applications Of H‐bonded Assembliesmentioning

confidence: 99%

Noncovalent Synthesis Using Hydrogen Bonding

Prins

Reinhoudt

Timmerman

2001

Angew. Chem. Int. Ed.

1,252

765

View full text Add to dashboard Cite

show abstract

“…Unlike traditional polymers, the chains use reversible interactions and are formed under equilibrium conditions. Polarized light microscopy studies on concentrated solutions of 61 reveal that the polymer displays a nematic liquid crystalline state, that is, the polymer chains self‐organize in a linear array 135. Chiral nematic (cholesteric) liquid crystalline phases emerge from analogous chiral monomers.…”

Section: Form To Functionmentioning

confidence: 99%

Molecular Encapsulation

Hof

Craig

Nuckolls

et al. 2002

Angew. Chem. Int. Ed.

Self Cite

954

473

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Louis Kahn, architect of the Salk Institute in La Jolla, said1 “even a common, ordinary brick wants to be something more than it is.” Suppose that were also true of molecules. We know that they can and do aggregate; they give complex structures, and by doing so they acquire new properties—functions that may not be apparent from a study of the individual components. This review is about molecular aggregates of a certain sort, namely, those that assemble and more or less completely surround other molecules. Taking part in this intimacy imparts unique properties to the participants, and new functions emerge from the aggregate as a whole. For the most part, we emphasize self‐complementary structures. Their ability to assemble—an expression of the molecule's desire to be something more than it is—results from instructions engineered into the molecules during their creation.

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“…eversible polymers offer many advantages over their traditional covalent counterparts because of their benign processing conditions and ability to organize rapidly into ordered systems with few imperfections (1)(2)(3). A range of noncovalent polymeric systems based on hydrogen bonding has appeared in recent years, and ordered films and fibers have been produced that display a rich array of structures (4)(5)(6)(7)(8).…”

mentioning

confidence: 99%

Emergent mechanical properties of self-assembled polymeric capsules

Castellano

Clark

Craig

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

118

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Synthetic self-assembled systems combine responsiveness and reversibility with the ability to perform chemical tasks such as molecular recognition and catalysis. An unmet challenge is the construction of polymeric materials that, like nature's tubulin, are simultaneously reversible and capable of useful physical tasks. We report here a class of reversibly formed polymers that show covalent-polymer mechanical integrity in solution and in the solid state. Non-Newtonian, polymeric behavior is observed despite the low molecular weight of the individual subunits and the seemingly weak forces holding the assemblies together. These polymers assemble through self-complementary hydrogen bonding and by physical encapsulation of small molecules; accordingly, the emergent macroscopic structure and function can be controlled by appropriate chemical signals. Reversible polymers offer many advantages over their traditional covalent counterparts because of their benign processing conditions and ability to organize rapidly into ordered systems with few imperfections (1-3). A range of noncovalent polymeric systems based on hydrogen bonding has appeared in recent years, and ordered films and fibers have been produced that display a rich array of structures (4-8). Stadler and coworkers (5, 9) were among the first to examine the solid-state bulk dynamic properties of polymers in which hydrogen bonds partly define the polymer main chain. Likewise, Meijer and coworkers (6) showed that reversible polymers constructed from strongly associating subunits (K a Ͼ 10 6 M Ϫ1 ) can exhibit increased viscosities in solution and covalent polymer viscoelasticity in the bulk. We have previously used NMR spectroscopy (10) and light scattering to verify the polymeric nature of assemblies composed of reversibly formed encapsulation complexes. All of these polymers are formed from specific interactions that are well-characterized in solution. Although weak, noncovalent forces are known to contribute to polymeric viscoelasticity in other systems, e.g., micelles (11) and organometallic assemblies (12), little is known about the mechanical properties of linear, hydrogen-bonded, main-chain polymers in solution (13). We now report that synthetic reversible polymeric capsules-the polycaps-evince mechanical properties and viscoelastic behavior that are characteristic of covalent polymers. Materials and Methods Proton 1H NMR spectra were recorded on a Bruker (Billerica, MA) DRX-600 (600 MHz) spectrometer. IR spectra were recorded on a Perkin-Elmer Paragon 1000PC Fourier-transform infrared spectrometer. Electrospray ionization mass spectrometry experiments were performed on an API III Perkin-Elmer SCIEX triple quadrupole mass spectrometer. Rheometry measurements were obtained with both parallel-plate and cone-andplate geometries on a Rheometric Scientific (Piscataway, NJ) SR-5000 dynamic stress rheometer. Rheology studies were performed in o-dichlorobenzene, which is both high boiling (180°C) and an excellent guest for the calixarene capsules. Temperature cont...

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Hierarchische Ordnung bei flüssigkristallinen Polykapseln

Cited by 27 publications

References 46 publications

Noncovalent Synthesis Using Hydrogen Bonding

Noncovalent Synthesis Using Hydrogen Bonding

Molecular Encapsulation

Emergent mechanical properties of self-assembled polymeric capsules

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