Polycaps: Reversibly formed polymeric capsules

Castellano, Ronald K.; Rudkevich, Dmitry M.; Rebek, Julius

doi:10.1073/pnas.94.14.7132

Cited by 205 publications

(151 citation statements)

References 20 publications

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“…Strikingly, two peaks were observed in the SEC traces of 7a in dilute (Ͻ10 Ϫ4 M) THF solutions. One peak corresponded to the same species seen in toluene (e.g., 12-mer), whereas the other had a very high polystyrene-based molecular weight (Ͼ85,000) consistent with formation of polymer (7) n (12,17,23). Another notable feature of the assemblies formed by 7 a-c is their exceptional stability-in particular the hexamer formed from 7c.…”

Section: Resultsmentioning

confidence: 92%

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

Corbin

Lawless

et al. 2002

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

170

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Hydrogen bond-mediated self-assembly is a powerful strategy for creating nanoscale structures. However, little is known about the fidelity of assembly processes that must occur when similar and potentially competing hydrogen-bonding motifs are present. Furthermore, there is a continuing need for new modules and strategies that can amplify the relatively weak strength of a hydrogen bond to give more stable assemblies. Herein we report quantitative complexation studies on a ureidodeazapterin-based module revealing an unprecedented stability for dimers of its self-complementary acceptoracceptor-donor-donor (AADD) array. Linking two such units together with a semirigid spacer that carries a first-, second-, or third-generation Fré chet-type dendron affords a ditopic structure programmed to self assemble. The specific structure that is formed depends both on the size of the dendron and the solvent, but all of the assemblies have exceptionally high stability. The largest discrete nanoscale assembly is a hexamer with a molecular mass of about 17.8 kDa. It is stabilized by 30 hydrogen bonds, including six AADD⅐DDAA contacts. The hexamer forms and is indefinitely stable in the presence of a hexamer containing six ADD⅐DAA hydrogen-bonding arrays. A t the most fundamental level, the readout of stored information in biochemical systems requires both a code and the machinery for expressing the code (1). Distinction at the molecular level is critical in such processes and in its simplest form involves a molecular recognition event. The code may be, for example, the primary sequence of a polypeptide, which through a series of recognition events folds into a specific secondary or tertiary structure, or it may be a linear array of recognition sites that are sequentially processed through a distinctive engagement at each site. However, a distinctive chemical process alone (e.g., DNA base pairing) is not sufficient. It must be coupled with a biological process (e.g., replication) to be considered authentic information retrieval.Inspired by nature's ability to create extraordinarily complex systems from comparatively simple information codes, and with an eye toward creating nanoscale devices (2), chemists have sought to develop small molecules capable of self-assembling into larger structures (3-10). Molecular recognition sites within these small molecules carry the code that guide the assembly. Thus, the information retrieval process is expressed through the formation of the self-assembled structure, which can further manifest itself through the bulk properties of the material formed (11,12). Despite the many successful examples that have appeared over the past decade, the power of this biomimetic self-assembly strategy has not been fully realized largely because of the limited number of recognition motifs available, and, in particular, their relatively low stability (4, 13). Moreover, nearly all self-assembling systems reported to date use a single type of distinction. Developing systems where bi-or polyinstructional codes guide ...

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Section: Resultsmentioning

confidence: 92%

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

Corbin

Lawless

et al. 2002

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

170

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“…Synthesis of the linear polycap monomer 1 has been previously reported (10). The tetravalent cross-linker 2 was achieved as follows.…”

Section: Materials and Methods Protonmentioning

confidence: 99%

“…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.…”

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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“…123 1 H NMR spectroscopy revealed the dynamic nature of the polycaps formed from two covalently linked calix [4]arene tetraureas, that can depolymerize upon the addition of monofunctional chain stoppers. 123 The polycaps are also able to encapsulate guests like benzene or p-difluorobenzene in their cavities.…”

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confidence: 99%

Controlling supramolecular polymerization through multicomponent self‐assembly

Besenius

2016

J. Polym. Sci. Part A: Polym. Chem.

128

102

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The self-assembly into supramolecular polymers is a process driven by reversible non-covalent interactions between monomers, and gives access to materials applications incorporating mechanical, biological, optical or electronic functionalities. Compared to the achievements in precision polymer synthesis via living and controlled covalent polymerization processes, supramolecular chemists have only just learned how to developed strategies that allow similar control over polymer length, (co)monomer sequence and morphology (random, alternating or blocked ordering). This highlight article discusses the unique opportunities that arise when coassembling multicomponent supramolecular polymers, and focusses on four strategies in order to control the polymer architecture, size, stability and its stimuli-responsive properties: (1) endcapping of supramolecular polymers, (2) biomimetic templated polymerization, (3) controlled selectivity and reactivity in supramolecular copolymerization, and (4) living supramolecular polymerization. In contrast to the traditional focus on equilibrium systems, our emphasis is also on the manipulation of selfassembly kinetics of synthetic supramolecular systems. V C 2016

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Polycaps: Reversibly formed polymeric capsules

Cited by 205 publications

References 20 publications

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

Emergent mechanical properties of self-assembled polymeric capsules

Controlling supramolecular polymerization through multicomponent self‐assembly

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