Polymer changes colour in the heat of the moment

Charlie Quigg writes about a hot Chemical Science article for Chemistry World

Scientists in China, the UK and the Netherlands have engineered a polydiacetylene polymer that reversibly changes colour within 1 second of being heated or cooled

Thermochromic polymers have a wide range of potential uses, from biological sensors to smart windows. However, the irregular structure and weak molecular interactions in established thermochromic polymers results in long response times, slow reversibility and a narrow working temperature range. 

The peptide linkers are stable, while the conjugated bonds within the alkyl chain undergo a reversible conformational transition

 


 

Read the full article in Chemistry World» 

Read the original journal article in Chemical Science – it’s free to access until 28th August:
Ultrafast and Reversible Thermochromism of Conjugated Polymer Material Based on Assembling of Peptide Amphiphiles
Zhengzhong Shao, Hui Guo, Jinming Zhang, David Porter, Huisheng Peng, Dennis Lowik, Yu Wang, Zhidong Zhang and Xin Chen  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC01696C, Edge Article

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Successful poster sessions attract the crowds at ISACS13

Two lively poster sessions saw the room packed out at the recent ISACS13 meeting on “Challenges in Inorganic and Materials Chemistry”, held in Dublin. Over 120 posters were presented, attracting large crowds and yielding 5 winners.   

Katie-Louise Finney of Durham University, UK was awarded the first prize, sponsored by Chemistry World, for her poster on PARASHIFT proton magnetic resonance imaging and spectroscopy. She receives £250 and a Chemistry World mug.  

Katie-Louise Finney with Neil Withers (Chemistry World Features Editor)  L-R: Lily Dixon, Pierre Sutra, Jane Hordern (Chemical Science Deputy Editor), Paolo Pirovano 

Lily Dixon (University of Cambridge, UK), Pierre Sutra (Université de Toulouse, France) and Dariusz Matoga (Jagiellonian University, Poland) each received a Chemical Science Poster Prize, while Paolo Pirovano (Trinity College Dublin, Ireland) was awarded a Dalton Transactions Poster Prize.  

The runners-up all receive a certificate and a copy of ‘The Case of the Poisonous Socks’ from the Royal Society of Chemistry’s popular science collection. 

Delegates at ISACS13 pack out the room at one of the poster sessions

You can find out more about ISACS13 and view the full programme online. 

The ISACS (International Symposia on Advancing the Chemical Sciences) series is organised in partnership with Chemical Science and brings together leading scientists from across the world. Find out more about upcoming conferences on the website, and view the speakers and programmes for previous events.

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Hot Chemical Science articles for July

All of the referee-recommended articles below are free to access until 20th August 2014

Aqueous photoinduced living/controlled polymerization: tailoring for bioconjugation
Jiangtao Xu, Kenward Jung, Nathaniel Alan Corrigan and Cyrille Boyer  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC01309C, Edge Article


Electric field control of the optical properties in magnetic mixed-valence molecules
Andrew Palii, Juan M. Clemente-Juan, Boris Tsukerblat and Eugenio Coronado  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC01056F, Edge Article


Multi-step and multi-component organometallic synthesis in one pot using orthogonal mechanochemical reactions
José G. Hernández, Ian S. Butler and Tomislav Friščić  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC01252F, Edge Article


Non-equilibrium transition state rate theory
Haidong Feng, Kun Zhang and Jin Wang  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00831F, Edge Article

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Lighting Up the Polymer World, Reversibly

Researchers from the UK have developed a polymeric system that exhibits reversible fluorescent behaviour. Anthea Blackburn writes more…

Fluorescent imaging is one of the most useful techniques in modern day medicine, as it provides us with a method of visualizing the inside of a body to allow for diagnosis and treatment of disease. Typically, an organic fluorophore is attached to a biomolecule that, upon introduction to the body, is able to interact with a specific type of molecule in the body, such as a cancerous cell or a molecule that carries out a particular and important function. More recently, in addition to the use of biomolecules, fluorescent labeling has turned to the polymer world for applications in targeted drug delivery or cell patterning to name but a few examples. Fluorescence becomes important in these applications, as the introduction of non-biological molecules to the body requires a method of locating them to track and monitor their activity.

There are a number of methods of introducing organic fluorophores to polymers, for example, polymerization of fluorescently labeled monomer units, end-group attachment, or post-synthetic modification, all of which offer advantages and disadvantages. The one factor that all of these approaches have in common however, is that one needs to beware of how the attachment of fluorophores, which are typically large, will change the chemistry of the polymer. It would therefore be advantageous if small, yet fluorescent, groups could be attached to polymers without otherwise changing their properties.

It is this interest in synthesising fluorescent polymers using small molecules that Mathew Robin and Rachel O’Reilly from the University of Warwick sought to tackle. They were able to demonstrate that the introduction of dithiomaleimide functional groups, which have a large Stokes shift (250 nm) and bright emission, to acrylate or methacrylate polymers did not change the properties of the polymer itself. Perhaps even more interestingly is that it was demonstrated that the functional groups could be introduced both pre-synthetically and post-synthetically. In this way, polymer fluorescence could be both turned on in a profluorescent polymer that contained a reactive dibromomaleimide monomer unit, as well as reversibly turned off through a dithiol exchange reaction to a non-fluorescent dithiomaleimide monomer unit.

The development of a relatively simple system whose fluorescence can be reversible turned on and off is an exciting step forward in developing polymers, especially since the end groups of this functionalised polymer allows for its further incorporation into more complex polymeric systems. These polymers could have applications in not only the biomedical uses discussed, but also in a numerous other applications such as organic electronic devices, sensing materials and polymer materials like nanoparticles and hydrogels.

Read this HOT Chemical Science Edge article in full for free*!

Fluorescent and chemico-fluorescent responsive polymers from dithiomaleimide and dibromomaleimide functional monomers

Mathew P. Robin and Rachel K. O’Reilly
Chem. Sci.20145, 2717.
DOI: 10.1039/C4SC00753K, Edge Article

About the Writer

Anthea Blackburn is a guest web writer for Chemical Science. Anthea is a graduate student hailing from New Zealand, studying at Northwestern University in the US under the tutelage of Prof. Fraser Stoddart (a Scot), where she is exploiting supramolecular chemistry to develop multidimensional systems and study the emergent properties that arise in these superstructures. When time and money allow, she is ambitiously attempting to visit all 50 US states before graduation.

*Access is free untill 08.08.14 through a registered RSC account – click here to register

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Small Molecule Mimics of Transport Proteins

Philip Gale, Chair of our sister Journal ChemSocRev, et al report the first use of thiosquaramides as anion receptors and pH-switchable anion transporters.

Many diseases are caused by faulty anion transport across cell membranes, such as faulty chloride transport leading to cystic fibrosis. Therefore, in recent years interest has grown in developing small molecule mimics of transport proteins that can be used to restore or disrupt the chemical processes within cells and thus cure or kill a range of diseases.

Researchers from the University of Southampton and the University of Sydney have produced a series of thiosquaramides which investigate pH dependent chloride transport properties. It was observed that the anion transport ability of the thiosquaramides was completely turned on below a pH of 7.2 but fully switched off at a pH value of 7.2 or higher. The developed thiosquaramides can promote chloride efflux mainly via a chloride/nitrate antiport process.

One of the thiosquaramide derivative with bound chloride anion

This paper provides one of the few examples of truly controllable and switchable anion transport by small synthetic molecules. Thiosquaramides form interesting targets for developing future biologically active anion transporters –  read the paper today to find out how to make them!

To read the details, check out the Chem Sci article in full for free:

Nathalie Busschaert, Robert B. P. Elmes, Dawid D. Czech, Xin Wu, Isabelle L. Kirby, Evan M. Peck, Kevin D. Hendzel, Scott K. Shaw, Bun Chan, Bradley D. Smith, Katrina A. Jolliffe and Philip A. Gale
DOI: 10.1039/C4SC01629G
About the Webwriter
Iain Larmour is a guest web writer for ChemSci. He has researched a wide variety of topics during his years in the lab including nanostructured surfaces for water repellency and developing nanoparticle systems for bioanalysis by surface enhanced optical spectroscopies. He currently works in science management. In his spare time he enjoys reading, photography, art and inventing.

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Hot Chemical Science articles for June

All of the referee-recommended articles below are free to access until 21st July:

A full-adder based on reconfigurable DNA-hairpin inputs and DNAzyme computing modules
Ron Orbach, Fuan Wang, Oleg Lioubashevski, R. D. Levine, Francoise Remacle and Itamar Willner  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00914B, Edge Article


Millisecond lifetime imaging with europium complex using a commercial confocal microscope under one or two-photon excitations
Olivier Maury, Alexandre Haefele, Simon Pascal, Chantal Andraud, Alexei Grichine, Alain DUPERRAY and Richard MICHEL  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00473F, Edge Article

 


Supramolecular chemistry with ureido-benzoic acids
E W Meijer, Anja R. A. Palmans, Wilco Appel, Bas FM de Waal, Marko Nieuwenhuizen and Martin Lutz  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00871E, Edge Article


Synthesis and Chemoselective Ligations of MIDA Acylboronates with O-Me Hydroxylamines
Hidetoshi Noda and Jeffrey W Bode  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00971A, Edge Article

  

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Artificial ion channels that work on a feedback loop

written by Cally Haynes, a Publishing Editor at the Royal Society of Chemistry

In nature, many cellular processes are controlled by structures that are only assembled when they are needed, in response to a chemical energy input. The structure (and hence the action of the structure) is maintained so long as the chemical energy input, or ‘fuel’ for the process is present. For example, microtubules can ‘grow’ or ‘shrink’ depending on the presence of guanosine triphosphate (GTP), and hence GTP serves as a ‘fuel’ for the function of the microtubules.

Inspired by this principle, Tom Fyles and his team from University of Victoria, Canada have used thiol–thioester exchange chemistry to assemble a metastable ion channel that disassembles over time in the absence of a chemical fuel.

In the scheme below, thiol 4 is not an active ion channel, but the addition of thioester 5 causes the formation of 3 by thiol-thioester exchange. 3 forms an active ion channel, but is metastable and therefore over time it disassembles into 4 + 6 which stops the ion transport. Adding more 5 (the fuel) will temporarily regenerate the ion transport as more C is formed.

While this system functions exactly as planned, its design was not without complications, says Fyles: “One setback was that these compounds do not work in vesicles so we had to develop reaction monitoring techniques using the bilayer clamp experiment.  That gives us exquisite sensitivity, but also allows us to detect very minor amounts of impurities.  So another setback was the observation that an oxidation impurity was vastly more active than the compounds we wanted to see.  This problem was easy enough to solve, but it took some time to recognize what was going on.”

This work also opens up exciting new avenues of investigation for the future for Fyles and his team. “The more general insight is that this system depends entirely on kinetic factors.  As chemists we are used to thinking about rates in terms of the reaction order and uniform reactant concentrations in the bulk.  Our system additionally shows the importance of local concentrations as opposed to the bulk concentration.  This introduces additional kinetic components related to diffusion.  The functioning of our system recorded using the bilayer clamp is largely controlled by diffusion processes, rather than the reaction kinetics we control in the design of the system.  This suggests that we might be able to make other systems that deliberately exploit non-uniform concentrations – yet another feature we can see in nature. Stay tuned.”

To download the full article for free*, click the link below:

Dissipative Assembly of a Membrane Transport System
A. K. Dambenieks, P. H. Q. Vu and T. M. Fyles
DOI: 10.1039/C4SC01258E

*Access is free untill the 17.07.14 through a registered RSC account – click here to register

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Excellent visibility for your research

We want our authors’ research to get the visibility and recognition it deserves.

Chemical Science is dedicated to publishing findings of exceptional significance from across the chemical sciences.

The graph below shows the number of citations to articles published in 2013 in Chemical Science and other leading general chemistry journals. 

It’s clear to see from this data that articles in Chemical Science are less likely to receive no citations and after just a few months of publication articles will be highly cited - 45% of 2013 Chemical Science articles have already received 5 or more citations.

Publishing your research in Chemical Science means your article will have excellent visibility and will be read and cited quickly by your colleagues.

Chemical Science Citations

Citations to articles published in 2013 (Data downloaded from ISI Web of Science on 6 June 2014)

Browse the latest articles from Chemical Science here


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Triptycene based hole transport materials for dye sensitized solar cells

Researchers from China have synthesized three novel hole-conducting molecules which may give rise to significant economic advantages for the production of dye sentisized solar cells. Web writer Kevin writes more…

Dye sensitized solar cells (DSSCs) are photovoltaic devices which use a sensitizer in combination with a photosensitive material and a wide band gap semiconductor to produce an electric current. Thin-film DSSCs can offer packaging and application opportunites, have potential as functional coatings, and exhibit high power conversion efficiencies (PCE) of up to 12-13%.

Current state-of-the-art dye sensitized solar cells are usually solid phase systems, removing any issues surrounding leakage of components or the corrosive nature of some electrolytes. In such configurations a constituent known as a hole transport material (HTM) is now commonly used instead of a liquid electrolyte.

In this Chemical Science Edge article, authors from the Energy Research Institute, Nanyang, and the Nanyang Technological University, Singapore, give details of a group of triptycene based molecules which, they claim, perform on a comparable level with the current best in class HTM, (spiro-OMeTAD). The materials described were prepared from a starting tri-iodotryptycene material which was derivatised using a variety of transformations including Stille and Suzuki coupling reactions. The materials contain diphenylamine moieties separated from the triptycene core by aromatic spacers, enabling charge transfer.

These materials were fabricated in a complex process into a typical DSSC, containing fluorine doped tin oxide, semiconducting titanium dioxide and lead iodide perovskite dye sensitizer material. Power conversion efficiencies are comparable to devices comprimising the best performing HTMs. For the T102 andT103 derivatives, PCEs were reported as 12.24 and 12.38%, comparable to devices fabricated with spiro-OMeTAD (12.78%). Without a HTM present the number falls to less than 5%.

This article presents details of promising HTM materials which may give rise to significant economic advantages for the production and commercialisation of solid state DSSCs, with current best in class performance levels.

Read this HOT Chemical Science Edge Article for free* today:

Novel hole transporting materials based on triptycene core for high efficiency mesoscopic perovskite solar cells

Anurag Krishna, Dharani Sabba, Hairong Li, Jun Yin, Pablo P. Boix, Cesare Soci, Subodh G. Mhaisalkar and  Andrew C. Grimsdale
DOI: 10.1039/C4SC00814F

About the webwriter

Kevin Murnaghan is a guest web-writer for Chemical Communications. He is currently a Research Chemist in the Adhesive Technologies Business Sector of Henkel AG & Co. KGaA, based in Düsseldorf, Germany. His research interests focus primarily on enabling chemistries and technologies for next generation adhesives and surface treatments. Any views expressed here are his personal ones and not those of Henkel AG & Co. KGaA.

*Access is free untill the 11.07.14 through a registered RSC account – click here to register

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Fighting cancer with artificial antigen-presenting cells

Researchers from the Netherlands discuss the development of artificial antigen-presenting cells

Antigen-presenting cells (ACPs) are key players in the immune systems fight against cancer. On detection of tumor tissues, these ACPs pick up antigenic fragments of the tumor cell, migrate to the lymphoid organs and present the antigen to T-cells which play a central role in cell mediated immunity. Therefore, artificial ACPs (aAPCs) are often used in the development of immune-mediated anti-cancer therapies as they show great potential to mimic antigen-presentation, promoting T-cell activation.

Carl Figdor, a world-class immunologist, and colleagues from Radbound University discuss the current status of aAPC development in a Chemical Science Perspective. This review is partly focused on the developments in nanoscience which might improve future designs for immune-mediated anti-cancer therapies.

As a synthetic mimic, aAPCs must encompass the three signals that natural APCs use to encourage T-cell activation. This perspective discusses how these signals have been incorporated into aAPC designs, but also how physical properties such a size and shape are essential for targeting the aAPCs to T-cell rich areas in vivo.

Artificial antigen-presenting cells have the potential to develop into a widespread and powerful therapeutic tool. To download the full perspective, click on the link below – access is free for a limited time only!

Joep van der Weijden, Leonie Paulis, Martijn Verdoes, Jan C M van Hest and Carl Figdor
DOI: 10.1039/C4SC01112K
Looking for the best articles at the chemistry-biology interface. Check out our Chemical Biology Themed Collection showcasing some of the great research papers and reviews published in Chemical Science, in the areas of chemical biology and bioinorganic chemistry.
*Access is free through a registered RSC account – click here to register
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