Low-molecular-weight gelators: Elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model

Andrew R. Hirst; Ian A. Coates; Thomas R. Boucheteau; Juan F. Miravet; Beatriu Escuder; Valeria Castelletto; Ian W. Hamley; David K. Smith

doi:10.1021/ja801804c

Low-molecular-weight gelators: Elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model

Andrew R. Hirst, Ian A. Coates, Thomas R. Boucheteau, Juan F. Miravet, Beatriu Escuder, Valeria Castelletto, Ian W. Hamley, David K. Smith

Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

This paper highlights the key role played by solubility in influencing gelation and demonstrates that many facets of the gelation process depend on this vital parameter. In particular, we relate thermal stability (T-gel) and minimum gelation concentration (MGC) values of small-molecule gelation in terms of the solubility and cooperative self-assembly of gelator building blocks. By employing a van't Hoff analysis of solubility data, determined from simple NMR measurements, we are able to generate T-calc values that reflect the calculated temperature for complete solubilization of the networked gelator. The concentration dependence of T-calc allows the previously difficult to rationalize "plateau-region" thermal stability values to be elucidated in terms of gelator molecular design. This is demonstrated for a family of four gelators with lysine units attached to each end of an aliphatic diamine, with different peripheral groups (Z or Bee) in different locations on the periphery of the molecule. By tuning the peripheral protecting groups of the gelators, the solubility of the system is modified, which in turn controls the saturation point of the system and hence controls the concentration at which network formation takes place. We report that the critical concentration (C-crit) of gelator incorporated into the solid-phase sample-spanning network within the gel is invariant of gelator structural design. However, because some systems have higher solubilities, they are less effective gelators and require the application of higher total concentrations to achieve gelation, hence shedding light on the role of the MGC parameter in gelation. Furthermore, gelator structural design also modulates the level of cooperative self-assembly through solubility effects, as determined by applying a cooperative binding model to NMR data. Finally, the effect of gelator chemical design on the spatial organization of the networked gelator was probed by small-angle neutron and X-ray scattering (SANS/SAXS) on the native gel, and a tentative self-assembly model was proposed.

Original language	English
Pages (from-to)	9113-9121
Number of pages	9
Journal	Journal of the American Chemical Society
Volume	130
Issue number	28
DOIs	https://doi.org/10.1021/ja801804c
Publication status	Published - 16 Jul 2008

Keywords

2-COMPONENT DENDRITIC GEL
GLYCOSYLATED AMINO-ACID
BUILDING-BLOCKS
PHASE MATERIALS
SUPRAMOLECULAR POLYMERS
FUNCTIONAL MATERIALS
FIBER NETWORKS
ARCHITECTURE
ORGANOGELS
RECOGNITION

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10.1021/ja801804c

http://pubs.acs.org/doi/abs/10.1021/ja801804c

Cite this

@article{c8748ec53ef14abda0b7f65fd12c0958,

title = "Low-molecular-weight gelators: Elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model",

abstract = "This paper highlights the key role played by solubility in influencing gelation and demonstrates that many facets of the gelation process depend on this vital parameter. In particular, we relate thermal stability (T-gel) and minimum gelation concentration (MGC) values of small-molecule gelation in terms of the solubility and cooperative self-assembly of gelator building blocks. By employing a van't Hoff analysis of solubility data, determined from simple NMR measurements, we are able to generate T-calc values that reflect the calculated temperature for complete solubilization of the networked gelator. The concentration dependence of T-calc allows the previously difficult to rationalize {"}plateau-region{"} thermal stability values to be elucidated in terms of gelator molecular design. This is demonstrated for a family of four gelators with lysine units attached to each end of an aliphatic diamine, with different peripheral groups (Z or Bee) in different locations on the periphery of the molecule. By tuning the peripheral protecting groups of the gelators, the solubility of the system is modified, which in turn controls the saturation point of the system and hence controls the concentration at which network formation takes place. We report that the critical concentration (C-crit) of gelator incorporated into the solid-phase sample-spanning network within the gel is invariant of gelator structural design. However, because some systems have higher solubilities, they are less effective gelators and require the application of higher total concentrations to achieve gelation, hence shedding light on the role of the MGC parameter in gelation. Furthermore, gelator structural design also modulates the level of cooperative self-assembly through solubility effects, as determined by applying a cooperative binding model to NMR data. Finally, the effect of gelator chemical design on the spatial organization of the networked gelator was probed by small-angle neutron and X-ray scattering (SANS/SAXS) on the native gel, and a tentative self-assembly model was proposed.",

keywords = "2-COMPONENT DENDRITIC GEL, GLYCOSYLATED AMINO-ACID, BUILDING-BLOCKS, PHASE MATERIALS, SUPRAMOLECULAR POLYMERS, FUNCTIONAL MATERIALS, FIBER NETWORKS, ARCHITECTURE, ORGANOGELS, RECOGNITION",

author = "Hirst, {Andrew R.} and Coates, {Ian A.} and Boucheteau, {Thomas R.} and Miravet, {Juan F.} and Beatriu Escuder and Valeria Castelletto and Hamley, {Ian W.} and Smith, {David K.}",

year = "2008",

month = jul,

day = "16",

doi = "10.1021/ja801804c",

language = "English",

volume = "130",

pages = "9113--9121",

journal = "Journal of the American Chemical Society",

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publisher = "American Chemical Society",

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T1 - Low-molecular-weight gelators

T2 - Elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model

AU - Hirst, Andrew R.

AU - Coates, Ian A.

AU - Boucheteau, Thomas R.

AU - Miravet, Juan F.

AU - Escuder, Beatriu

AU - Castelletto, Valeria

AU - Hamley, Ian W.

AU - Smith, David K.

PY - 2008/7/16

Y1 - 2008/7/16

N2 - This paper highlights the key role played by solubility in influencing gelation and demonstrates that many facets of the gelation process depend on this vital parameter. In particular, we relate thermal stability (T-gel) and minimum gelation concentration (MGC) values of small-molecule gelation in terms of the solubility and cooperative self-assembly of gelator building blocks. By employing a van't Hoff analysis of solubility data, determined from simple NMR measurements, we are able to generate T-calc values that reflect the calculated temperature for complete solubilization of the networked gelator. The concentration dependence of T-calc allows the previously difficult to rationalize "plateau-region" thermal stability values to be elucidated in terms of gelator molecular design. This is demonstrated for a family of four gelators with lysine units attached to each end of an aliphatic diamine, with different peripheral groups (Z or Bee) in different locations on the periphery of the molecule. By tuning the peripheral protecting groups of the gelators, the solubility of the system is modified, which in turn controls the saturation point of the system and hence controls the concentration at which network formation takes place. We report that the critical concentration (C-crit) of gelator incorporated into the solid-phase sample-spanning network within the gel is invariant of gelator structural design. However, because some systems have higher solubilities, they are less effective gelators and require the application of higher total concentrations to achieve gelation, hence shedding light on the role of the MGC parameter in gelation. Furthermore, gelator structural design also modulates the level of cooperative self-assembly through solubility effects, as determined by applying a cooperative binding model to NMR data. Finally, the effect of gelator chemical design on the spatial organization of the networked gelator was probed by small-angle neutron and X-ray scattering (SANS/SAXS) on the native gel, and a tentative self-assembly model was proposed.

AB - This paper highlights the key role played by solubility in influencing gelation and demonstrates that many facets of the gelation process depend on this vital parameter. In particular, we relate thermal stability (T-gel) and minimum gelation concentration (MGC) values of small-molecule gelation in terms of the solubility and cooperative self-assembly of gelator building blocks. By employing a van't Hoff analysis of solubility data, determined from simple NMR measurements, we are able to generate T-calc values that reflect the calculated temperature for complete solubilization of the networked gelator. The concentration dependence of T-calc allows the previously difficult to rationalize "plateau-region" thermal stability values to be elucidated in terms of gelator molecular design. This is demonstrated for a family of four gelators with lysine units attached to each end of an aliphatic diamine, with different peripheral groups (Z or Bee) in different locations on the periphery of the molecule. By tuning the peripheral protecting groups of the gelators, the solubility of the system is modified, which in turn controls the saturation point of the system and hence controls the concentration at which network formation takes place. We report that the critical concentration (C-crit) of gelator incorporated into the solid-phase sample-spanning network within the gel is invariant of gelator structural design. However, because some systems have higher solubilities, they are less effective gelators and require the application of higher total concentrations to achieve gelation, hence shedding light on the role of the MGC parameter in gelation. Furthermore, gelator structural design also modulates the level of cooperative self-assembly through solubility effects, as determined by applying a cooperative binding model to NMR data. Finally, the effect of gelator chemical design on the spatial organization of the networked gelator was probed by small-angle neutron and X-ray scattering (SANS/SAXS) on the native gel, and a tentative self-assembly model was proposed.

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KW - GLYCOSYLATED AMINO-ACID

KW - BUILDING-BLOCKS

KW - PHASE MATERIALS

KW - SUPRAMOLECULAR POLYMERS

KW - FUNCTIONAL MATERIALS

KW - FIBER NETWORKS

KW - ARCHITECTURE

KW - ORGANOGELS

KW - RECOGNITION

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DO - 10.1021/ja801804c

M3 - Article

SN - 0002-7863

VL - 130

SP - 9113

EP - 9121

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 28

ER -

Low-molecular-weight gelators: Elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model

Abstract

Keywords

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