Spatiotemporal Control of Supramolecular Polymerization and Gelation of Metal-Organic Polyhedra

In coordination-based supramolecular materials such as metallogels, simultaneous temporal and spatial control of their assembly remains challenging. Here, we demonstrate that the combination of light with acids as stimuli allows for the spatiotemporal control over the architectures, mechanical properties, and shape of porous soft materials based on metal-organic polyhedra (MOPs). First, we show that the formation of a colloidal gel network from a preformed kinetically trapped MOP solution can be triggered upon addition of trifluoroacetic acid (TFA), and that acid concentration determines the reaction kinetics. As determined by time-resolved dynamic light scattering, UV-vis absorption and 1H NMR spectroscopies and rheology measurements, the consequences of the increase in acid concentration are (i) an increase in the cross-linking between MOPs; (ii) a growth in the size of the colloidal particles forming the gel network; (iii) an increase in the density of the colloidal network; and (iv) a decrease in the ductility and stiffness of the resulting gel. We then demonstrate that irradiation of a dispersed photoacid generator, pyranine, allows the spatiotemporal control of the gel formation by locally triggering the self-assembly process. Using this methodology, we show that the gel can be patterned into a desired shape. Such precise positioning of the assembled structures, combined with the stable and permanent porosity of MOPs, could allow their integration into devices for applications such as sensing, separation, catalysis, or drug release.

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Understanding of the Multiscale Self-Assembly of Metal-Organic Polyhedra Towards Functionally Graded Porous Gels

10.26434/chemrxiv.9746177.v1 ◽

2019 ◽

Author(s):

alexandre legrand ◽

Gavin A. Craig ◽

Mickaele Bonneau ◽

Saori Minami ◽

Kenji Urayama ◽

...

Keyword(s):

Self Assembly ◽

Energy Transport ◽

Soft Materials ◽

Functionally Graded ◽

Colloidal Gels ◽

Time Resolved ◽

Colloidal Aggregation ◽

Synthetic Materials ◽

Multiple Length Scales ◽

Metal Organic

Spatial heterogeneity and gradients within porous materials are key for controlling their mechanical properties and mass/energy transport, both in biological and synthetic materials. However, it is still challenging to induce such complexity in well-defined microporous materials such as crystalline metal-organic frameworks (MOFs). Here we show a method to generate a continuous gradient of porosity over multiple length scales by taking advantage of the amorphous nature of supramolecular polymers based on metal-organic polyhedra (MOPs). First, we use time-resolved dynamic light scattering (TRDLS) to elucidate the mechanism of hierarchical self-assembly of MOPs into colloidal gels and to understand the relationship between the MOP concentrations and the architecture of the resulting colloidal networks. These features directly impact on the viscoelastic response of the gels and their mechanical strength. We then show that gradients of stiffness and porosity can be created within the gel by applying centrifugal force at the point of colloidal aggregation. These results with the creation of asymmetric and graded pore configuration in soft materials could lead to the emergence of advanced properties that are coupled to asymmetric molecule/ion transport as seen in biological systems.

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Controlled sequential assembly of metal-organic polyhedra into colloidal gels with high chemical complexity

10.33774/chemrxiv-2021-6dhhs ◽

2021 ◽

Author(s):

Min Ying Tsang ◽

Shun Tokuda ◽

Po-Chun Han ◽

Zaoming Wang ◽

Alexandre Legrand ◽

...

Keyword(s):

Colloidal Particles ◽

Soft Materials ◽

Chemical Components ◽

Colloidal System ◽

Synthetic Process ◽

Chemical Complexity ◽

Porous Networks ◽

Synthetic Strategy ◽

Colloidal Gel ◽

Metal Organic

Assembling many chemical components into a material in a controlled manner is one of the biggest challenges in chemistry. Particularly porous materials with multivariate character within their scaffolds are expected to demonstrate synergistic properties. In this study, we show a synthetic strategy to construct porous networks with multiple chemical components. By taking advantage of the hierarchical nature of a colloidal system based on metal-organic polyhedra (MOPs), we developed a two-step assembly process to form colloidal networks; assembling of MOPs with the organic linker to the formation of MOP network as a colloidal particle, followed by further connecting colloids by additional crosslinkers, leading to colloidal networks. This synthetic process allows not only for the use of different organic linkers for connecting MOPs and colloidal particles, respectively, but for assembling different colloidal particles formed by various MOPs. The proof-of-concept of this tuneable multivariate colloidal gel system offers an alternative to developing functional porous soft materials with multifunction.

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Understanding of the Multiscale Self-Assembly of Metal-Organic Polyhedra Towards Functionally Graded Porous Gels

10.26434/chemrxiv.9746177 ◽

2019 ◽

Author(s):

alexandre legrand ◽

Gavin A. Craig ◽

Mickaele Bonneau ◽

Saori Minami ◽

Kenji Urayama ◽

...

Keyword(s):

Self Assembly ◽

Energy Transport ◽

Soft Materials ◽

Functionally Graded ◽

Colloidal Gels ◽

Time Resolved ◽

Colloidal Aggregation ◽

Synthetic Materials ◽

Multiple Length Scales ◽

Metal Organic

Spatial heterogeneity and gradients within porous materials are key for controlling their mechanical properties and mass/energy transport, both in biological and synthetic materials. However, it is still challenging to induce such complexity in well-defined microporous materials such as crystalline metal-organic frameworks (MOFs). Here we show a method to generate a continuous gradient of porosity over multiple length scales by taking advantage of the amorphous nature of supramolecular polymers based on metal-organic polyhedra (MOPs). First, we use time-resolved dynamic light scattering (TRDLS) to elucidate the mechanism of hierarchical self-assembly of MOPs into colloidal gels and to understand the relationship between the MOP concentrations and the architecture of the resulting colloidal networks. These features directly impact on the viscoelastic response of the gels and their mechanical strength. We then show that gradients of stiffness and porosity can be created within the gel by applying centrifugal force at the point of colloidal aggregation. These results with the creation of asymmetric and graded pore configuration in soft materials could lead to the emergence of advanced properties that are coupled to asymmetric molecule/ion transport as seen in biological systems.

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Porous Colloidal Hydrogels Formed by Coordination-Driven Self-Assembly of Charged Metal-Organic Polyhedra

10.26434/chemrxiv.13621220.v1 ◽

2021 ◽

Author(s):

Zaoming Wang ◽

Gavin Craig ◽

alexandre legrand ◽

Frederik Haase ◽

Saori Minami ◽

...

Keyword(s):

Self Assembly ◽

Soft Materials ◽

Building Blocks ◽

Internal Cavity ◽

Hydroxyl Groups ◽

Gel Formation ◽

Gas Sorption ◽

Coordination Cages ◽

Metal Organic ◽

Supramolecular Polymerization

Introduction of porosity into supramolecular gels endows soft materials with functionalities for molecular encapsulation, release, separation and conversion. Metal-organic polyhedra (MOPs), discrete coordination cages containing an internal cavity, have recently been employed as building blocks to construct polymeric gel networks with potential porosity. However, most of the materials can only be synthesized in organic solvents, and the examples of porous, MOP-based hydrogels are scarce. Here, we demonstrate the fabrication of porous hydrogels based on [Rh2(OH-bdc)2]12, a rhodium-based MOP containing hydroxyl groups on its periphery (OH-bdc = 5-hydroxy-1,3-benzenedicarboxylate). By simply deprotonating [Rh2(OH-bdc)2]12 with the base NaOH, the supramolecular polymerization between MOPs and organic linkers can be induced in the aqueous solution, leading to the kinetically controllable formation of hydrogels with hierarchical colloidal networks. When heating the deprotonated MOP, Nax[Rh24(O-bdc)x(OH-bdc)24-x], to induce gelation, the MOP was found to partially decompose, affecting the mechanical property of the resulting gels. By applying a post-synthetic deprotonation strategy, we show that the deprotonation degree of the MOP can be altered after the gel formation without serious decomposition of the MOPs. Gas sorption measurements confirmed the permanent porosity of the corresponding aerogels obtained from these MOP-based hydrogels, showing potentials for applications in gas sorption and catalysis.

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Soft Materials with Diverse Suprastructures via the Self-Assembly of Metal–Organic Complexes

Accounts of Chemical Research ◽

10.1021/acs.accounts.8b00663 ◽

2019 ◽

Vol 52 (3) ◽

pp. 802-817 ◽

Cited By ~ 57

Author(s):

Yan Sun ◽

Chongyi Chen ◽

Peter J. Stang

Keyword(s):

Self Assembly ◽

Soft Materials ◽

The Self ◽

Organic Complexes ◽

Metal Organic

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Multiscale Structural Control of Linked Metal-Organic Polyhedra Gel by Aging-Induced Linkage-Reorganization

10.26434/chemrxiv.14481855 ◽

2021 ◽

Author(s):

Zaoming Wang ◽

Christian Villa Santos ◽

alexandre legrand ◽

Frederik Haase ◽

Yosuke Hara ◽

...

Keyword(s):

Structural Control ◽

Colloidal Particles ◽

Hierarchical Structures ◽

Porous Metal ◽

Soft Materials ◽

Supramolecular Polymer ◽

Polymer Systems ◽

Multiple Length Scales ◽

Metal Organic ◽

Supramolecular Networks

Assembly of permanently porous metal-organic cages with functional polymers forms soft supramolecular networks featuring both porosity and processability. However, the amorphous nature of such soft materials complicates their characterization and thus limits structural control. Here we demonstrated that aging is an effective strategy to control the hierarchical network of supramolecular gels, which are assembled from organic ligands as linkers and metal-organic polyhedra (MOP) as junctions. Normally, the initial gel formation by rapid gelation leads to a kinetically trapped structure with low controllability. Through a controlled post-synthetic aging process, we show that it is possible to tune the network of the linked MOP gel over multiple length scales. This process allows control on the molecular-scale rearrangement of interlinking MOPs, mesoscale fusion of colloidal particles and macroscale densification of the whole colloidal network. In this work we elucidate the relationships between the gel properties, such as porosity and rheology, and their hierarchical structures, which suggest that porosity measurement can be used as a powerful tool to characterize the microscale structural transition of the amorphous gels. This aging strategy can be applied in other supramolecular polymer systems particularly containing kinetically controlled structures and shows an opportunity to engineer the structure and porosity of amorphous porous soft materials for further applications.

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Mechanical Properties of Colloidal Gels

MRS Proceedings ◽

10.1557/proc-155-83 ◽

1989 ◽

Vol 155 ◽

Cited By ~ 14

Author(s):

W.-H. Shih ◽

J. Liu ◽

W. Y. Shih ◽

S. I. Kim ◽

M. Sarikaya ◽

...

Keyword(s):

Power Law ◽

Particle Concentration ◽

Colloidal Particles ◽

Colloidal Suspension ◽

The Other ◽

Colloidal Gels ◽

Yield Strain ◽

Colloidal Gel ◽

Type Of Behavior ◽

Gel Network

A colloidal suspension can be either dispersed or flocculated depending on the interaction between the colloidal particles. If the interaction is repulsive, particles can relax to the minimum of the potential due to their neighboring particles, and the system can reach an equilibrium dispersed state. In the case of attractive interaction, particles form aggregates that settle to the bottom of the container. As the concentration of particles is increased, the overcrowding of the aggregates produces a continuous network throughout the suspension before they settle and a colloidal gel is formed. A major difference between a colloidal gel and a colloidal suspension is that the gel can sustain finite stress and is therefore viscoelastic. Previously we studied the storage modulus and the yield strain of boehmite gels and found that they are related to the particle concentration in a power-law fashion [1]. Similar scaling behavior of the shear modulus was found for other colloidal particulate networks by Buscall et al. [2]. We developed a scaling theory [1] which successfully explains the experimental results on boehmite gels. The theory further predicts that there can be two types of power-law behavior depending on the relative elastic strength of the clusters to that of the links between clusters within the gel network. Furthermore, there can be a crossover from one type of behavior to the other as the particle concentration is varied.

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Multiscale Structural Control of Linked Metal-Organic Polyhedra Gel by Aging-Induced Linkage-Reorganization

10.26434/chemrxiv.14481855.v1 ◽

2021 ◽

Author(s):

Zaoming Wang ◽

Christian Villa Santos ◽

alexandre legrand ◽

Frederik Haase ◽

Yosuke Hara ◽

...

Keyword(s):

Structural Control ◽

Colloidal Particles ◽

Hierarchical Structures ◽

Porous Metal ◽

Soft Materials ◽

Supramolecular Polymer ◽

Polymer Systems ◽

Multiple Length Scales ◽

Metal Organic ◽

Supramolecular Networks

Assembly of permanently porous metal-organic cages with functional polymers forms soft supramolecular networks featuring both porosity and processability. However, the amorphous nature of such soft materials complicates their characterization and thus limits structural control. Here we demonstrated that aging is an effective strategy to control the hierarchical network of supramolecular gels, which are assembled from organic ligands as linkers and metal-organic polyhedra (MOP) as junctions. Normally, the initial gel formation by rapid gelation leads to a kinetically trapped structure with low controllability. Through a controlled post-synthetic aging process, we show that it is possible to tune the network of the linked MOP gel over multiple length scales. This process allows control on the molecular-scale rearrangement of interlinking MOPs, mesoscale fusion of colloidal particles and macroscale densification of the whole colloidal network. In this work we elucidate the relationships between the gel properties, such as porosity and rheology, and their hierarchical structures, which suggest that porosity measurement can be used as a powerful tool to characterize the microscale structural transition of the amorphous gels. This aging strategy can be applied in other supramolecular polymer systems particularly containing kinetically controlled structures and shows an opportunity to engineer the structure and porosity of amorphous porous soft materials for further applications.

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Gamma Radiation- and Ultraviolet-Induced Polymerization of Bis(amino acid)fumaramide Gel Assemblies

Polymers ◽

10.3390/polym14010214 ◽

2022 ◽

Vol 14 (1) ◽

pp. 214

Author(s):

Tomislav Gregorić ◽

Janja Makarević ◽

Zoran Štefanić ◽

Mladen Žinić ◽

Leo Frkanec

Keyword(s):

Amino Acid ◽

Ultraviolet Radiation ◽

Self Assembly ◽

Gamma Ray ◽

Methyl Esters ◽

Three Dimensional ◽

Soft Materials ◽

Polymerization Reaction ◽

Vinyl Esters ◽

Gel Network

Controlling the polymerization of supramolecular self-assembly through external stimuli holds great potential for the development of responsive soft materials and manipulation at the nanoscale. Vinyl esters of bis(leu or val)fumaramide (1a and 2a) have been found to be gelators of various organic solvents and were applied in this investigation of the influence of organogelators’ self-assembly on solid-state polymerization induced by gamma and ultraviolet irradiation. Here, we report our investigation into the influences of self-assemblies of bis(amino acid vinyl ester)fumaramides on gamma-ray- and ultraviolet-induced polymerization. The gelator molecules self-assembled by non-covalent interactions, mainly through hydrogen bonds between the amide group (CONH) and the carboxyl group (COO), thus forming a gel network. NMR and FTIR spectroscopy were used to investigate and characterize supramolecular gels. TEM and SEM microscopy were used to investigate the morphology of gels and polymers. Morphology studies showed that the gels contained a filamentous structure of nanometer dimensions that was exhaustive in a three-dimensional network. The prepared derivatives contained reactive alkyl groups suitable for carrying out the polymerization reaction initiated by gamma or ultraviolet radiation in the supramolecular aggregates of selected gels. It was found that the polymerization reaction occurred only in the network of the gel and was dependent on the structure of aggregates or the proximity and orientation of double bonds in the gel network. Polymers were formed by the gels exposure to gamma and ultraviolet radiation in toluene, and water/DMF gels with transcripts of their gel structure into polymers. The polymeric material was able to immobilize various solvents by swelling. Furthermore, methyl esters of bis(leu and val)fumaramide (1b and 2b) were synthesized; these compounds showed no gelling properties, and the crystal structure of the valine derivative 2b was determined.

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