Physical Aspects of Polymer Science

This week saw the 25th biennial meeting of the UK’s Polymer Physics Group (PPG) take place at the University of Surrey. The PPG is part of the Institute of Physics and has strong ties with the Royal Society of Chemistry. This year celebrates the 25th meeting of the group and is also the 50th anniversary of the UK’s first ever meeting on the physics of polymers, which was held in Bristol in 1961. For those interested the proceedings of that first meeting were published in the British Journal of Applied Physics.

Along with a full oral and poster programme and invited talks from Olli Ikkala, Cait MacPhee, William Koros and Dieter Richter, a number of prizes were awarded at the conference. Prof. Tom McLeish from the University of Durham was awarded the Founders Prize. He is the sixth recipient of this award, which is given to a scientist who has made an outstanding contribution to Polymer Physics in the UK or Ireland.

Katherine Thomas (me!) was awarded the Students Prize for her paper on the non-equilibrium behaviour observed in thin polymer films published in Phys. Rev. E. This work looks at the interplay of the polymer film deposition procedure, the resulting non-equilibrium behaviour and the relaxation towards thermal equilibrium. A follow up paper to this work on the direct measurement of stresses in spin-cast films was recently published in Soft Matter. A previous post on this topic can be found here.

The exchange lecture with the American Physical Society Division of Polymer (DPoly) was given by Bradley Olsen. Proteins and enzymes are interesting materials for photovoltaics, catalysts and CO2 reduction and sequestration. Olsen is interested in incorporating proteins into materials so that they can be used in the above applications. He does this by forming protein-polymer diblock copolymers. These block copolymers can then be self-assembled enabling their structure to be easily controlled. His recent papers in Soft Matter can be found here and here.

The first place poster prize was awarded to Mike Smith at the University of Nottingham. Smith had three posters at the conference on ‘Optical properties of large amyloid spherulites’, ‘ Stretching dense colloidal suspensions: from flow to fracture’ and ‘Cracking in thin films of colloidal particles on elastomeric substrates’.

Congratulations to all the prize winners. The conference was very successful and highly enjoyable. It was one of the best conferences I have been to (and not just because they gave me a prize). I would highly recommend that those interested attend their next meeting in two years time.

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Top Ten most-read Soft Matter articles in July

This month sees the following articles in Soft Matter that are in the top ten most accessed in July:

Soft microorigami: self-folding polymer films
Leonid Ionov
Soft Matter, 2011, 7, 6786-6791
DOI:10.1039/c1sm05476g 

Biopolymers in nanopores: challenges and opportunities 
Hemant Kumar, Yves Lansac, Matthew A. Glaser and Prabal K. Maiti 
Soft Matter, 2011, 7, 5898-5907
DOI:10.1039/c0sm01517b 

Stimulus responsive nanogels for drug delivery 
Liusheng Zha, Brittany Banik and Frank Alexis
Soft Matter, 2011, 7, 5908-5916
DOI:10.1039/c0sm01307b 

Janus particles at an oil–water interface 
Bum Jun Park, Teresa Brugarolas and Daeyeon Lee 
Soft Matter, 2011, 7, 6413-6417 
DOI:10.1039/c1sm05460k 

Biomimetic morphogenesis of micropottery: helical coiling of mesostructured silica nanofibers 
Longping Zhou, Jianfeng Ye, Guosong Hong and Limin Qi 
Soft Matter, 2011, Advance Article 
DOI:10.1039/c1sm05593c 

Fabrication and evaluation of reduction-sensitive supramolecular hydrogel based on cyclodextrin/polymer inclusion for injectable drug-carrier application 
Jiahui Yu, Honglei Fan, Jin Huang and Jinghua Chen 
Soft Matter, 2011, 7, 7386-7394 
DOI:10.1039/c1sm05426k 

Bio-inspired anisotropic micro/nano-surface from a natural stamp: grasshopper wings 
Tong Zhang, Mingzhu Li, Bin Su, Changqing Ye, Kan Li, Weizhi Shen, Li Chen, Zhongxin Xue, Shutao Wang and Lei Jiang 
Soft Matter, 2011, 7, 7973-7975 
DOI:10.1039/c1sm05366c 

Self-assembly of double hydrophilic block copolymers in concentrated aqueous solution 
Adam Blanazs, Nicholas J. Warren, Andrew L. Lewis, Steven P. Armes and Anthony J. Ryan 
Soft Matter, 2011, 7, 6399-6403 
DOI:10.1039/c1sm05771e 

Mechanics of random fiber networks—a review 
R. C. Picu
Soft Matter, 2011, 7, 6768-6785 
DOI:10.1039/c1sm05022b 

Biomimetic microlens array with antireflective “moth-eye” surface 
Doo-Hyun Ko, John R. Tumbleston, Kevin J. Henderson, Larken E. Euliss, Joseph M. DeSimone, Rene Lopez and Edward T. Samulski 
Soft Matter, 2011, 7, 6404-6407 
DOI:10.1039/c1sm05302g 

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 or alternatively email us  your suggestions.

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Triblock copolymers—Yield stress fluids—Lipid rafts

Read for free until 30 September>>>

Amphiphilic triblock copolymers: A new study demonstrates that the length of a polyethylene glycol (PEG) spacer has a crucial impact on the association behaviour of temperature sensitive triblock copolymers at elevated temperatures. Findings show that a short PEG length promotes formation of interchain complexes at high temperatures. Atoosa Maleki, Kaizheng Zhu, Ramón Pamies, Ricardo Rodríguez Schmidt, Anna-Lena Kjøniksen, Göran Karlsson, José G. Hernández Cifre, José García de la Torre and Bo Nyström, Soft Matter, 2011, DOI: 10.1039/C1SM05679D

Yield stress fluids: Stress-induced fluidization of a simple yield stress fluid, namely a carbopol microgel, is addressed through extensive rheological measurements coupled to simultaneous temporally and spatially resolved velocimetry. A clear link between the transient regime of the fluidization process and the steady-state rheology is presented for the first time. Thibaut Divoux, Catherine Barentin and Sébastien Manneville, Soft Matter, 2011, DOI: 10.1039/C1SM05607G

Lipid rafts: Ligand-induced transbilayer coupling of rafts is simulated in this Hot Article. Using coarse grained molecular dynamics (CGMD) simulations the authors show that raft registration arises spontaneously in bilayers with a calcium- or ligand-crosslinked ordered phase segregating from a liquid disordered phase. Diego A. Pantano, Preston B. Moore, Michael L. Klein and Dennis E. Discher, Soft Matter, 2011, DOI: 10.1039/C1SM05490B

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Active and passive liquid crystals

Example of nematic texture and defect structures observed in LC confined in micro-channels.

Example of nematic texture and defect structures observed in liquid crystals confined in micro-channels.

Can the flow of active and passive liquid crystals be accurately described using the same theoretical model? This was the question posed by Miha Ravnik, from the University of Oxford in a recent seminar. The motivation for this work is to improve the understanding of liquid crystal (LC) flow in micro-channels. The coupling of material flow with orientation in LC, via internal material stress, is very interesting both technologically, as a driving mechanism for controlling material flow, and for understanding the behaviour of artificial and biological swimmers. Flow is also important for understanding topological defects in LC (Soft Matter doi: 10.1039/B810933H).

The model of Ravnik is based on the phenomenological Beris-Edwards model, solved using a hybrid lattice-Boltzmann method. The equations couple the orientation, described by an order parameter, with the flow velocity field, which is modelled using a generalised Navier-Stokes description. The orientation describes the LC alignment in the flow, the molecular field and the internal motility of the LC (this is zero for passive LC). The results show that for both passive and active LC the behaviour is dependent on the magnitude of the driving flow and the dimensions of the channel. This includes the LC orientation and flow profiles and the position of defect lines.

Similar behaviour was recently observed experimentally by Sengupta et al. (Soft Matter doi: 10.1039/C1SM05052D), who studied the flow of nematic LC through micro-channels. Different textures and defect structures were observed to develop depending on the channel dimensions and the flow rate applied. Some very nice movies, showing the formation of these structures, can be found as supplementary information with the article.

Miha Ravnik is also interested in understanding the behaviour of topological defect loops seen when colloidal particles are added to liquid crystals (Soft Matter doi: 10.1039/B913065A). The controlled manipulation of these defect loops was discussed in a previous post.

A talk given by Ravnik on liquid crystal colloids can be found here. The talk presents routes for the functionalisation of colloidal particles and continuum liquid crystals.

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Hot Articles: Liquid crystals, anti-pathogenic and stimuli-responsive hydrogels

Read free until 23 September>>>

Antimicrobial and antiviral hydrogels: This brief review provides some illustrative examples of different types of antimicrobial (antibacterial/antifungal) and antiviral hydrogels. The triggered response of the  hydrogels is discussed and a focus is placed on formulation principles, and on how the physicochemical properties of such hydrogels influence their antimicrobial/antiviral action. Martin Malmsten, Soft Matter, 2011, DOI: 10.1039/C1SM05809F

Thermal liquid crystal phases: An interaction assisted approach for realization of biaxiality in smectic A phases is demonstrated in addition to the effectiveness of perfluoroarene-arene and C-H/F interactions as the intermolecular interactions. The slow rotation of the molecules showed unique phenomena such as no clear odd–even effect in their clearing and melting points. Keiki Kishikawa, Takahiro Inoue, Yoshiyuki Sasaki, Sumihiro Aikyo, Masahiro Takahashi and Shigeo Kohmoto, Soft Matter, 2011, 7, 7532-7538, DOI: 10.1039/C1SM05887H

Stimuli-responsive hydrogels: Researchers have functionalised poly(N-isopropylacrylamide) gel with spirobenzopyrans and evaluated the effects of spontaneous ring-opening rates of the photo-chromic molecules on the light-responsive volume change of the subsequent gels. Rates of reswelling from the light-induced shrunken state of the spirobenzopyran-functionalized gels increased with increasing ring-opening rates of spirobenzopyrans in the gels. Taku Satoh, Kimio Sumaru, Toshiyuki Takagi and Toshiyuki Kanamori, Soft Matter, 2011, DOI: 10.1039/C1SM05797A

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Editorial Board Member wins Soft Matter prize

Professor Alejandro Rey (McGill University), who is on the Editorial Board for Soft Matter has won the Stanley George Mason Award. The Canadian Society of Rheology presents the award every three years to a Canandian scientist who has distinguished themselves in the field of Rheology. Read more here.

Soft Matter recently published a Themed Issue on the Dynamics and Rheology of Complex Fluid-Fluid Interfaces, see here…

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Polyelectrolytes and soft matter nanofabrication

Lipid bilayers, vesicles and lipid-polyelectrolyte phases forming on polyelectrolyte multilayers.

Sergio Moya is a soft matter scientist at the CIC biomaGUNE in San Sebastian, Spain. His research focuses on the nano-fabrication of soft matter for various applications including medical applications, to form membranes for water filtration and to study nano-toxicity. Moya is particularly interested in utilising polyelectrolytes as they are “easy to assemble, pattern and synthesise”.

Moya studies polyelectrolyte growth and behaviour using, amongst other things, a quartz crystal micro-balance in tandem with ellipsometry and atomic force microscopy. This allows the growth and assembly of polyelectrolyte multilayers to be monitored along with their mechanical properties and water content (doi: 10.1021/ma1015984).

Polyelectrolyte multilayers have a number of different uses including the non-covalent functionalisation of particles (doi: 10.1021/la803360n). Once coated with polyelectrolytes Moya has shown that the core particles can subsequently be removed without damaging the multilayer coating.  The multilayer can also be selectively removed or attached using the appropriate surfactants (doi:10.1021/jp908608u). Polyelectrolyte multilayers have also been used to support lipid bilayer membranes and study their formation (Soft Matter, doi: 10.1039/b805754k). Bilayers, absorbed vesicles and 3D lipid-polyelectrolyte phases have all been seen to form (see figure).

Finally, in a recent Soft Matter paper, not discussed in his talk, Moya has shown that the toxicity of carbon nanotubes can be reduced when coated with polyelectrolyte-lipid layers (Soft Matter, doi: 10.1039/C0SM01511C).

Sergio Moya recently gave a seminar at the Max-Planck Institute for Dynamics and Self-Organization as part of the Dynamics of Complex Fluids seminar series.

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Soft Matter poster prize winner

Congratulations to Rona Chandrawati from The University of Melbourne, Australia, for winning a Soft Matter poster prize at ESF-EMBO Symposium: Biological Surfaces and Interfaces held at Hotel Eden Roc, Sant Feliu de Guixols, Spain.

The title of Chandrawati’s winning poster was: Capsosomes: Enzyme-Loaded Liposomal Subcompartments within Polymer Carrier Capsules.

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Hot Articles on Biomimetic Soft Matter

These Hot Articles are from an upcoming Themed Issue on “Biomimetic Soft Matter” with Guest Editor Professor Ian Hamley (University of Reading and Diamond Light Source, UK). Keep an eye out for this and other Soft Matter Themed Issues here.

Proteins in biomimetic membranes: promises and facts. A Review on proteins immobilized on surfaces in different orientations to form protein-tethered bilayer lipid membranes, with the protein as the essential building block. Renate L. C. Naumann, Christoph Nowak and Wolfgang Knoll, Soft Matter, 2011, DOI: 10.1039/C1SM05626C

A reversible enzymatic trigger is reported by Samuel Stupp and co-workers, which controls the assembly and disassembly of peptide amphiphile nanostrucutres. This ability to control nanostructure through an enzymatic switch could allow for the preparation of highly sophisticated and biomimetic materials that incorporate a biological sensing capability to enable therapeutic specificity. Matthew J. Webber, Christina J. Newcomb, Ronit Bitton and Samuel I. Stupp, Soft Matter, 2011, DOI: 10.1039/C1SM05610G

These papers can be read for free until September 16.

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EPFDC-2011

Images of two nematodes (Panagrellus redivivus) merging.

Last week (8-12th August) saw the 5th European postgraduate fluid dynamics conference (EPFDC-2011) take place in Goettingen, Germany. The conference was jointly hosted by the Institute of Aerodynamics and Flow technology and the Max Planck Institute for Dynamics and Self-Organization. Organised by postgraduate students, the conference is an open-forum for PhD students allowing them to present their results in talks and posters to an audience of their peers.

The sessions were wide ranging in their themes, which included turbulent flows, applied aerodynamics, hydrodynamic stability and geophysical flows. The conference also featured talks on the swimming of micro-organisms, biofluid dynamics and the patterning of polymer melt films.

The hydrodynamics of swimming micro-organisms

Douglas Brumley is a PhD student at DAMTP, University of Cambridge. His talk focused on his work on the low Reynolds number swimmer Volvox carteri. Volvox forms spherical colonies of up to 50,000 biflagelated cells. The cells on the surface of the colony beat their flagella in a coordinated fashion, resulting in a net fluid motion around the colony. Various pictures and videos of the flagella and fluid motion can be found on the DAMTP website. Brumley’s work focuses on modelling the flow fields around the Volvox colonies and characterising the metachronal wave propagating on its surface.

Recent publications in Soft Matter on similar low Reynolds number swimmers include: Hydrodynamic synchronization at low Reynolds number doi: 10.1039/C0SM01121E, The collective motion of nematodes in a thin liquid layer doi: 10.1039/C0SM01236J and Swimmer-tracer scattering at low Reynolds number doi: 10.1039/C0SM00164C.

Flow through shunts at low Reynolds number

Adriana Setchi is currently a PhD student at Imperial College London. In her talk Setchi discussed her work on the modelling of flow in shunts in the small intestine. Shunts are used by doctors in the small intestine to by-pass diseased areas, or to shorten the intestine for weight loss. While medical doctors are able to carry out the implantation of shunts effectively, the dynamics of flow in these by-passes are not well understood. To model the flow, Setchi finds solutions to the Papkovich-Fadle-eigenfunction and applies them to various flow scenarios.

Recent publications in Soft Matter on dynamics in the small intestine include: The adsorption and competitive adsorption of bile salts and whey protein at the oil-water interface doi: 10.1039/C1SM05840A, Transitions in the internal structure of lipid droplets during fat digestion doi:10.1039/C0SM00491J.

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