A simple route to responsive, particle-stabilized foams using bare silica nanoparticles

Web writer Rob Woodward highlights a hot article from the journal


Defined as bubbles of gas in liquid-film matrix, foams are important precursors in the food and cosmetic industry and for the production of macroporous materials. In this report a simple, effective route to silica nanoparticle stabilised responsive aqueous foams has been demonstrated by the Binks group. Stimuli-responsive surface active particles have generated growing interest in recent years, utilising triggers including pH, temperature and light irradiation to create ‘switchable’ foams, i.e. the ability to “switch-off” the foaming capability of the particles. However, the production of responsive surface active particles usually involves surface coating of mineral particles or the complicated synthesis of functional polymer particles.

In order to address this problem Binks et al. utilise the interaction of N’-dodecyl-N,N-dimethylacetamidinium bicarbonate, a responsive surfactant, with anionic silica nanoparticles in water. By exposure to either CO2 or N2 the responsive surfactant can be switched between a cationic species and a surface-inactive neural form, respectively. On the formation of the cationic species, complexation of the surfactant to anionic silica nanoparticle surfaces gives an in situ increase in the hydrophobicity of the silica, yielding surface-active nanoparticles. Agitation of the resulting complexed system gives foams, however, on exposure to N2 the responsive surfactant returns to its neutral state and desorbs from the surface of the silica particles, resulting in desorption of the particles from the water-air interface.

This simple route to switchable particle-stabilized aqueous foams removes the need for the complicated synthesis of particles as ‘bare’ silica nanoparticles can be used. The synergistic effect of the responsive surfactant and the nanoparticles also allows for the production of foams using a much lower concentration of surfactant than in a responsive-surfactant system alone.

Micrographs of the bubbles in foams produced by shaking 10 cm3 of a dispersion of 0.5 wt% particles in a surfactant solution at different concentrations in bottles (25 cm3) taken immediately after shaking. Surfactant concentrations from A to F are: 0.1, 0.2, 0.3, 0.6, 1.0 and 2.0 mM.

To find out more read the full article:

Responsive aqueous foams stabilised by silica nanoparticles hydrophobised in situ with a switchable surfactant

Yue Zhu, Jianzhong Jiang, Zhenggang Cui and Bernie Binks

Soft Matter, 2014, Accepted Manuscript

DOI: 10.1039/C4SM01970A

This post was written by web writer Rob Woodward. Rob is currently based in Imperial College London working in the Polymer and Composite Engineering (PaCE) group. Rob has a background in both responsive polymeric surfactants and microporous organic polymers for carbon capture and storage.

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On polydispersity and the hard sphere glass transition – an overview of a hot article

On polydispersity and the hard sphere glass transition, Emanuela Zaccarelli, Siobhan M. Liddle and Wilson C. K. Poon, Soft Matter, 2014

DOI: 10.1039/C4SM02321H

The aim of this work was to investigate the dynamics of polydisperse hard spheres at high packing fractions φ. The effects of polydispersity and the detailed shape of the particle size distribution (PSD) were studied.


The glass transition is not fully understood despite many decades of research. The discovery that hard-spheres, sterically-stabilised polymethylmethacrylate (PMMA) colloids, underwent kinetic arrest at a packing fraction of φ = φg ≈ 0.58 led to hard sphere colloids becoming the preferred method to test mode coupling theory (MCT). This is a significant piece of work by Emanuela Zaccarelli, Siobhan M. Liddle and Wilson C. K. Poon who are the first to present simulations of a polydisperse system of hard spheres with a size distribution essentially identical to the experimental data. The findings of the authors are novel and very important, they also put forward a new interpretation of what is going on in glass transition of MCT experiments. Assumptions with regard to PSD are not made and a model as close to the experimental one as possible is designed.

Event-driven Molecular Dynamics (MD) simulations of hard spheres with different PSD were performed. Experimentally obtained PSD from ≈ 2200 PMMA particles were measured by transmission electron microscopy (TEM). N = 2309 particles were simulated with the experimental PSD, measurement noise was included to produce a realistic system representation. N = 2000 particles taken from Gaussian and top hat distributions were considered for comparison.

It was found that a mixed state of ergodic small particles and glassy large particles in a window of concentrations is present and results in a hybrid dynamical state that is fluid for a long time but shows an unusual type of ageing. The breakdown of the MCT-predictions is due to the existence of partial decoupling, which is not accounted for in the monodisperse-version of MCT. However, the results of MCT are recovered once the polydispersity is reduced. There is a non-monotonic dependence of the quality of the glass former on the polydispersity index, s. When s = 0, the system is prone to crystallization and strong glasses are formed when s = <8%. The glass transition is smeared out due to the emergence of the “ageing liquid” for higher values of s as well as for samples drawn from peaked distributions. The precise form of the size distribution is relevant, a peaked distribution that allows a distinction between small and large particles is essential but this is not the case in the top hat particle distribution.

In conclusion, at a fixed relative standard deviation of the PSD the exact shape of the PSD has little influence on the general behaviour of the dynamics, large differences between the dynamics of “small” and “large” particles are found for realistic PSD shapes.

The glass transition is smeared out in polydisperse hard spheres due to decoupling between small and large particles

Please follow the link for the full article.

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12th International Conference on Materials Chemistry (MC12) – call for abstracts

We are delighted to announce that 12th International Conference on Materials Chemistry (MC12) will be held at the University of York on 20 – 23 July 2015. Abstracts are now invited for this event so submit today and take advantage of this excellent opportunity to present your work alongside scientists from across the globe.

This cutting edge international research conference is organised around four exciting and diverse areas of the application of materials chemistry. One prominent theme at MC12 is Soft Matter Materials, which aims to cover the wide and varied aspects of soft matter materials showing the power of the interplay between a priori design and physical function. Visit http://rsc.li/mc12 to find out more and submit your abstract today.

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HOT articles for November!

Molecular geometry, twist-bend nematic phase and unconventional elasticity: a generalised
Maier–Saupe theory Cristina Greco, Geoffrey R. Luckhurst and Alberta Ferrarini 

Graphical abstract: Molecular geometry, twist-bend nematic phase and unconventional elasticity: a generalised Maier–Saupe theory

 
“Crystal-clear” liquid–liquid transition in a tetrahedral fluid
Francis W. Starr and Francesco Sciortino

Graphical abstract: “Crystal-clear” liquid–liquid transition in a tetrahedral fluid

These articles will be free until 1st December 2014


Peeling-angle dependence of the stick-slip instability during adhesive tape peeling
Marie-Julie Dalbe, Stéphane Santucci, Loïc Vanel and Pierre-Philippe Cortet  

Graphical abstract: Peeling-angle dependence of the stick-slip instability during adhesive tape peeling

Multi-blob coarse graining for ring polymer solutions
Arturo Narros, Christos N. Likos, Angel J. Moreno and Barbara Capone 

Graphical abstract: Multi-blob coarse graining for ring polymer solutions

These articles will be free until 9th  December 2014


 
Relating foam and interfacial rheological properties of β-lactoglobulin solutions
M. Lexis and N. Willenbacher

Graphical abstract: Relating foam and interfacial rheological properties of β-lactoglobulin solutions

 
Controlling mechanisms in directional growth of aggregated archaeal cells
Viktor Milkevych and Damien J. Batstone

Graphical abstract: Controlling mechanisms in directional growth of aggregated archaeal cells

These articles will be free until 16th  December 2014


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Making light of food allergies

Written by Katie Bayliss

Researchers in Spain are taking steps towards ‘allergy-free’ food, by treating allergy-inducing proteins with a pulsed light treatment that makes them easier to digest.

 The scientists at the University of Granada and the AZTI-Tecnalia Food Research Institute studied the protein β-lactoglobulin, which acts as an excellent emulsifier in milk and other food products but has a compact structure that defies easy digestion. This lack of digestibility is linked to allergenicity, explains team member Julia Maldonado-Valderrama: ‘If the protein is not completely digested, the body reacts as if it is an allergen, which can trigger an allergic reaction.’ Pre-treatment could break down the protein structure before eating; however, it’s a balancing act. ‘If you break the protein down too much in order to facilitate digestion, they lose their functionality and can’t be used to make foams and emulsions in food products,’ says Maldonado-Valderrama.

To read the full article please visit Chemistry World.

Improved digestibility of β-lactoglobulin by pulsed light processing: dilatational and shear study
Teresa del Castillo-Santaella, Esther Sanmartín-Sierra, Miguel Cabrerizo-Vílchez, J Arboleya and Julia Maldonado-Valderrama 
Soft Matter, 2014
DOI: 10.1039/C4SM01667J, Paper

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Block Copolymer Spheres or Block Copolymer Worms: Which Pickering Emulsifier Has More Backbone?

Web writer Rob Woodward highlights a hot article from the journal

This recent publication from the Armes group investigates the ability of a number of amphiphilic block copolymer nanoparticles to stabilize n-dodecane-in-water emulsions. The aim of the work was to compare spherical and worm-like nano-structures and their efficiency as Pickering emulsifiers, i.e. the ability of these solid particles to adsorb irreversibly at the liquid-liquid interface to form a Pickering emulsion.

Graphical abstract: Are block copolymer worms more effective Pickering emulsifiers than block copolymer spheres?

In previous work by the University of Sheffield group, a number of both linear and branched block copolymers were produced in the form of vesicular structures. It was found that branching was necessary in order to prevent the vesicles dissociating into individual copolymer chains when exposed to high-shear homogenization. In this work linear and branched analogues of the copolymer poly(glycerol monomethacrylate)–poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) are synthesized as both spherical and worm-like nanoparticles. Armes et al. report that the linear nano-structures are not sufficiently robust enough to survive the high-shear conditions necessary for emulsification, whereas the cross-linked copolymer structures are more likely to retain their morphologies and yield genuine Pickering emulsions. Spherical and worm-like structures are provided greater covalent stabilization via chemical cross-linking, allowing structures to survive homogenization as with the vesicles reported previously.

The use of the more hydrophobic poly(benzyl methacrylate) (PBzMA) in place of PHPMA was also investigated in order to examine if increased amphiphilicity could enhance the stability of linear nano-objects in the absence of chemical cross-linking. Both the spherical and worm-like structures comprised of these linear polymer chains formed stable Pickering emulsions, suggesting that branching is not mandatory for the formation of the particulate surfactants.

Due to strong adsorption at the liquid-liquid interface and their ability to produce smaller droplets at a given nanoparticle concentration, it is concluded that branched copolymers with worm-like morphologies are the more effective Pickering emulsifiers. This is also aided by the suggestion that they are at least as efficiently adsorbed at the interface as their spherical analogues.

K. L. Thompson, C. J. Mable, A. Cockram, N. J. Warren, V. J. Cunningham, E. R. Jones, R. Verber and S. P. Armes

This post was written by web writer Rob Woodward. Rob is currently based in Imperial College London working in the Polymer and Composite Engineering (PaCE) group. Rob has a background in both responsive polymeric surfactants and microporous organic polymers for carbon capture and storage.

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HOT articles for October!

 
Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal
Alenka Mertelj, Natan Osterman, Darja Lisjak and Martin Čopič 

 Graphical abstract: Magneto-optic and converse magnetoelectric effects in a ferromagnetic liquid crystal
 
Trajectories of probe spheres in generalized linear viscoelastic complex fluids
Manas Khan and Thomas G. Mason  

Graphical abstract: Trajectories of probe spheres in generalized linear viscoelastic complex fluids

These articles will be free until 29th October 2014


Capillary tube wetting induced by particles: towards armoured bubbles tailoring
Farzam Zoueshtiagh, Michael Baudoin and David Guerrin

Graphical abstract: Capillary tube wetting induced by particles: towards armoured bubbles tailoring

 
Measuring cellular forces using bis-aliphatic hydrazone crosslinked stress-relaxing hydrogels
D. D. McKinnon, D. W. Domaille, T. E. Brown, K. A. Kyburz, E. Kiyotake, J. N. Cha and K. S. Anseth

Graphical abstract: Measuring cellular forces using bis-aliphatic hydrazone crosslinked stress-relaxing hydrogels

These articles will be free until 13th November 2014


Chiral random grain boundary phase of achiral hockey-stick liquid crystals
Dong Chen, Haitao Wang, Min Li, Matthew A. Glaser, Joseph E. Maclennan and Noel A. Clark

Graphical abstract: Chiral random grain boundary phase of achiral hockey-stick liquid crystals
 
Self-assembly of hard helices: a rich and unconventional polymorphism
Hima Bindu Kolli, Elisa Frezza, Giorgio Cinacchi, Alberta Ferrarini, Achille Giacometti, Toby S. Hudson, Cristiano De Michele and Francesco Sciortino

Graphical abstract: Self-assembly of hard helices: a rich and unconventional polymorphism

These articles will be free until 19th November 2014


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HOT articles for September!

Engineering entropy in soft matter: the bad, the ugly and the good
Fernando A. Escobedo 

Graphical abstract: Engineering entropy in soft matter: the bad, the ugly and the good

3D Viscoelastic traction force microscopy
Jennet Toyjanova, Erin Hannen, Eyal Bar-Kochba, Eric M. Darling, David L. Henann and Christian Franck

Graphical abstract: 3D Viscoelastic traction force microscopy

These articles will be free until 10th October 2014


 
Approach to universal self-similar attractor for the levelling of thin liquid films
Michael Benzaquen, Paul Fowler, Laetitia Jubin, Thomas Salez, Kari Dalnoki-Veress and Elie Raphaël  

Graphical abstract: Approach to universal self-similar attractor for the levelling of thin liquid films
 
Discovery of a tetracontinuous, aqueous lyotropic network phase with unusual 3D-hexagonal symmetry
Gregory P. Sorenson, Adam K. Schmitt and Mahesh K. Mahanthappa  

Graphical abstract: Discovery of a tetracontinuous, aqueous lyotropic network phase with unusual 3D-hexagonal symmetry

These articles will be free until 15th October 2014


Extracting the dynamic correlation length of actin networks from microrheology experiments
Adar Sonn-Segev, Anne Bernheim-Groswasser and Yael Roichman

Graphical abstract: Extracting the dynamic correlation length of actin networks from microrheology experiments

Tuning the surface properties of hydrogel at the nanoscale with focused ion irradiation
Y. Kim, A. Y. Abuelfilat, S. P. Hoo, A. Al-Abboodi, B. Liu, Tuck Ng, P. Chan and J. Fu  

Graphical abstract: Tuning the surface properties of hydrogel at the nanoscale with focused ion irradiation 
 

These articles will be free until 22nd  October 2014


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Top 10 most-read Soft Matter articles – Q2 2014

This month sees the following articles in Soft Matter that are in the top ten most accessed from April – June:

Edible nanoemulsions: Fabrication, properties, and functional performance 
David Julian McClements    
Soft Matter, 2011,7, 2297-2316 
DOI: 10.1039/C0SM00549E 

Amphiphilic Janus Particles at Fluid Interfaces 
Ankit Kumar, Bum Jun Park, Fuquan Tu and Daeyeon Lee 
Soft Matter, 2013,9, 6604-6617 
DOI: 10.1039/C3SM50239B 

Control of Mesogen Configuration in Colloids of Liquid Crystalline Polymers 
Sönke Haseloh, Paul van der Schoot and Rudolf Zentel 
Soft Matter, 2010,6, 4112-4119 
DOI: 10.1039/C0SM00125B 

Directed Self-Assembly of Block Copolymers: A Tutorial Review of Strategies for Enabling Nanotechnology with Soft Matter 
Hanqiong Hu, Manesh Gopinadhan and Chinedum O. Osuji  
Soft Matter, 2014,10, 3867-3889 
DOI: 10.1039/C3SM52607K 

Manipulation of micro- and nanostructure motion with magnetic fields 
Roger S. M. Rikken, Roeland J. M. Nolte, Jan C. Maan, Jan C. M. van Hest, Daniela A. Wilson and Peter C. M. Christianen   
Soft Matter, 2014,10, 1295-1308 
DOI: 10.1039/C3SM52294F 

Polyelectrolyte adsorption, interparticle forces, and colloidal aggregation 
Istvan Szilagyi, Gregor Trefalt, Alberto Tiraferri, Plinio Maroni and Michal Borkovec    
Soft Matter, 2014,10, 2479-2502 
DOI: 10.1039/C3SM52132J 

Bioinspired materials that self-shape through programmed microstructures 
André R. Studart and Randall M. Erb 
Soft Matter, 2014,10, 1284-1294 
DOI: 10.1039/C3SM51883C 

Traction Force Microscopy in Physics and Biology 
Robert W. Style, Rostislav Boltyanskiy, Guy K. German, Callen Hyland, Christopher W. MacMinn, Aaron F. Mertz, Larry A. Wilen, Ye Xu and Eric R. Dufresne 
Soft Matter, 2014,10, 4047-4055 
DOI: 10.1039/C4SM00264D 

Gel architectures and their complexity 
Walter Richtering and Brian R. Saunders 
Soft Matter, 2014,10, 3695-3702 
DOI: 10.1039/C4SM00208C 

Self-assembly of poly(benzyl methacrylate)-block-poly(2-(dimethylamino)ethyl methacrylate) diblock copolymer films at the air/water interface and deposition on solid substrates via Langmuir-Blodgett transfer: aggregation behavior, morphological characteristics and subphase pH effects 
P. Cecilia dos Santos Claro, Marcos E. Coustet, Carolina Diaz, Eliana Maza, M. Susana Cortizo, Félix G. Requejo, Lía I. Pietrasanta, Marcelo Ceolín and Omar Azzaroni 
Soft Matter, 2013,9, 10899-10912 
DOI: 10.1039/C3SM52336E 

Why not take a look at the articles today and blog your thoughts and comments below.

Fancy submitting an article to Soft Matter? Then why not submit to us today!

To keep up-to-date with all the latest research, sign up for the Soft Matter e-Alert or RSS feeds or follow Soft Matter on Twitter or Facebook

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Colloidal caterpillars get a wiggle on

Article written by Katie Bayliss.

Researchers have devised a new method to transport micro cargo – by attaching it to chains of colloidal particles that wiggle their way through liquid crystals.

The research team, led by Hiroshi Orihara from Hokkaido University, Japan, and Christian Bahr from the Max Planck Institute for Dynamics and Self-Organization, Germany, created colloidal ‘caterpillars’ from surface-modified silica particles which self-assemble into chains when placed in a liquid crystal medium. To make them move, the team exploit an effect called electrohydrodynamic convection (EHC), where the application of an electric field creates a convective pattern of parallel rolls within the medium. The caterpillars travel in an undulating motion across successive rolls, driven by a combination of hydrodynamic flow and electric field effects. Excitingly, the caterpillars can be attached to and used to transport larger particles and liquid droplets, which are in themselves too big to be moved by the EHC rolls.

To read the full article visit Chemistry World.

Colloidal Caterpillars for Cargo Transportation
Yuji Sasaki, Yoshinori Takikawa, VSR Jampani, Hikaru Hoshikawa, Takafumi Seto, Christian Bahr, Stephan Herminghaus, Yoshiki Hidaka and Hiroshi Orihara  
Soft Matter, 2014, Accepted Manuscript
DOI: 10.1039/C4SM01354A, Paper

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