Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

Autoren

Pol Besenius
Isja de Feijter
Nico AJM Sommerdijk
Paul HH Bomans
Anja RA Palmans

DOI

10.3791/3975

eISSN

1940-087X

Ausgabe der Veröffentlichung

66

Zeitschrift

Journal of Visualized Experiments

Sprache

en

Online publication date

2012

Status

Published online

Herausgeber

MyJove Corporation

Herausgeber URL

http://dx.doi.org/10.3791/3975

Datum der Datenerfassung

2023

Titel

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

Datenquelle: Crossref

Abstract

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult. At the same time, the ability to do so is highly important in view of a number of applications in functional soft matter including electronics, biomedical engineering, and sensors. In the past, successful strategies to control the size and shape of supramolecular polymers typically focused on the use of templates, end cappers or selective solvent techniques. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing electrostatic repulsive interactions on the hydrophilic rim and attractive non-covalent forces within the hydrophobic core of the polymerizing building block, we manage to create small and discrete spherical objects. Increasing the salt concentration to screen the charges induces a sphere-to-rod transition. Intriguingly, this transition is expressed in an increase of cooperativity in the temperature-dependent self-assembly mechanism, and more stable aggregates are obtained. For our study we select a benzene-1,3,5-tricarboxamide (BTA) core connected to a hydrophilic metal chelate via a hydrophobic, fluorinated L-phenylalanine based spacer (Scheme 1). The metal chelate selected is a Gd(III)-DTPA complex that contains two overall remaining charges per complex and necessarily two counter ions. The one-dimensional growth of the aggregate is directed by π-π stacking and intermolecular hydrogen bonding. However, the electrostatic, repulsive forces that arise from the charges on the Gd(III)-DTPA complex start limiting the one-dimensional growth of the BTA-based discotic once a certain size is reached. At millimolar concentrations the formed aggregate has a spherical shape and a diameter of around 5 nm as inferred from (1)H-NMR spectroscopy, small angle X-ray scattering, and cryogenic transmission electron microscopy (cryo-TEM). The strength of the electrostatic repulsive interactions between molecules can be reduced by increasing the salt concentration of the buffered solutions. This screening of the charges induces a transition from spherical aggregates into elongated rods with a length > 25 nm. Cryo-TEM allows to visualise the changes in shape and size. In addition, CD spectroscopy permits to derive the mechanistic details of the self-assembly processes before and after the addition of salt. Importantly, the cooperativity -a key feature that dictates the physical properties of the produced supramolecular polymers- increases dramatically upon screening the electrostatic interactions. This increase in cooperativity results in a significant increase in the molecular weight of the formed supramolecular polymers in water.

Addresses

Organic Chemistry Institute and CeNTech, Westfälische Wilhelms-Universität Münster.

Autoren

Pol Besenius
Isja de Feijter
Nico AJM Sommerdijk
Paul HH Bomans
Anja RA Palmans

DOI

10.3791/3975

eISSN

1940-087X

Externe Identifier

PubMed Identifier: 22895608
PubMed Central ID: PMC3476753

Open access

true

ISSN

1940-087X

Ausgabe der Veröffentlichung

66

Zeitschrift

Journal of visualized experiments : JoVE

Schlüsselwörter

Water
Benzamides
Gadolinium DTPA
Phenylalanine
Chelating Agents
Cryoelectron Microscopy
Microscopy, Electron, Transmission
Circular Dichroism
Models, Molecular
Hydrophobic and Hydrophilic Interactions

Sprache

eng

Medium

Electronic

Online publication date

2012

Open access status

Open Access

Paginierung

e3975

Datum der Veröffentlichung

2012

Status

Published

Publisher licence

CC BY-NC-ND

Datum der Datenerfassung

2012

Titel

Controlling the size, shape and stability of supramolecular polymers in water.

Sub types

Video-Audio Media
research-article
Journal Article

Files

https://www.jove.com/pdf/3975/controlling-size-shape-stability-supramolecular-polymers https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22895608/pdf/?tool=EBI https://europepmc.org/articles/PMC3476753?pdf=render

Datenquelle: Europe PubMed Central

Abstract

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult. At the same time, the ability to do so is highly important in view of a number of applications in functional soft matter including electronics, biomedical engineering, and sensors. In the past, successful strategies to control the size and shape of supramolecular polymers typically focused on the use of templates, end cappers or selective solvent techniques. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing electrostatic repulsive interactions on the hydrophilic rim and attractive non-covalent forces within the hydrophobic core of the polymerizing building block, we manage to create small and discrete spherical objects. Increasing the salt concentration to screen the charges induces a sphere-to-rod transition. Intriguingly, this transition is expressed in an increase of cooperativity in the temperature-dependent self-assembly mechanism, and more stable aggregates are obtained. For our study we select a benzene-1,3,5-tricarboxamide (BTA) core connected to a hydrophilic metal chelate via a hydrophobic, fluorinated L-phenylalanine based spacer (Scheme 1). The metal chelate selected is a Gd(III)-DTPA complex that contains two overall remaining charges per complex and necessarily two counter ions. The one-dimensional growth of the aggregate is directed by π-π stacking and intermolecular hydrogen bonding. However, the electrostatic, repulsive forces that arise from the charges on the Gd(III)-DTPA complex start limiting the one-dimensional growth of the BTA-based discotic once a certain size is reached. At millimolar concentrations the formed aggregate has a spherical shape and a diameter of around 5 nm as inferred from (1)H-NMR spectroscopy, small angle X-ray scattering, and cryogenic transmission electron microscopy (cryo-TEM). The strength of the electrostatic repulsive interactions between molecules can be reduced by increasing the salt concentration of the buffered solutions. This screening of the charges induces a transition from spherical aggregates into elongated rods with a length > 25 nm. Cryo-TEM allows to visualise the changes in shape and size. In addition, CD spectroscopy permits to derive the mechanistic details of the self-assembly processes before and after the addition of salt. Importantly, the cooperativity -a key feature that dictates the physical properties of the produced supramolecular polymers- increases dramatically upon screening the electrostatic interactions. This increase in cooperativity results in a significant increase in the molecular weight of the formed supramolecular polymers in water.

Autoren

Pol Besenius
Isja de Feijter
Nico AJM Sommerdijk
Paul HH Bomans
Anja RA Palmans

Autoren-URL

https://www.ncbi.nlm.nih.gov/pubmed/22895608

DOI

10.3791/3975

eISSN

1940-087X

Externe Identifier

PubMed Central ID: PMC3476753

Ausgabe der Veröffentlichung

66

Zeitschrift

J Vis Exp

Schlüsselwörter

Benzamides
Chelating Agents
Circular Dichroism
Cryoelectron Microscopy
Gadolinium DTPA
Hydrophobic and Hydrophilic Interactions
Microscopy, Electron, Transmission
Models, Molecular
Phenylalanine
Water

Sprache

eng

Country

United States

Paginierung

e3975

PII

3975

Datum der Veröffentlichung

2012

Status

Published online

Datum, an dem der Datensatz öffentlich gemacht wurde

2012

Titel

Controlling the size, shape and stability of supramolecular polymers in water.

Sub types

Journal Article
Video-Audio Media

Datenquelle: PubMed

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

Files

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