Focus on: Polymeric Composite Materials

A composite material contains two or more constituents which when combined afford significantly different material properties than the individual components. Well-known composites include concrete, plywood and fibre-reinforced plastics. With regard to polymeric composite materials, they usually consist of fillers dispersed in a polymer matrix to improve desired mechanical properties of the polymer material. Recently, research efforts have also focused on nanocomposites, where the filler has at least one dimension in the nano-scale, for example, nanoparticles, carbon nanotubes, 2D-sheets, such as graphene oxide, and nanofibres. These nano-fillers have shown huge improvements to material properties at low mass fractions, primarily due to the high surface area to volume ratio that nanomaterials possess. The increased interfacial area between the nanomaterial and continuous polymer matrix results in increased polymer-filler strength. Various applications have been proposed for nanocomposites: biomedical applications, waste water treatment, structural materials to name but a few.

Each of the highlighted articles this month report polymeric nanocomposites with improved properties such as increased strength, thermal stability, and desired adsorption behaviour when compared to the non-composite materials.

ToC image for article 1

1. Enhancement of the crosslink density, glass transition temperature, and strength of epoxy resin by using functionalized graphene oxide co-curing agents, Jin Won Yu, Jin Jung, Yong-Mun Choi, Jae Hun Choi, Jaesang Yu, Jae Kwan Lee, Nam-Ho You, Munju Goh, Polym. Chem., 2016, 7, 36-43.

Graphene oxide (GO) was incorporated into epoxy resins through functionalisation of the edge of the GO with amino groups, subsequently utilised for reaction with epoxy groups present in the polymer matrix. The incorporation of the modified GO into the resin improved the tensile strength and thermal properties of the materials. Higher crosslinking densities were also observed due to the covalent linking of the GO thanks to the amino groups introduced.

2. Tailored high performance shape memory epoxy–silica nanocomposites. Structure design, S. Ponyrko, R. K. Donato, L. Matějka, Polym. Chem., 2016, 7, 560-572.

The authors describe the preparation of epoxy resins containing silica nanoparticles and shape memory behavior of the materials was investigated. The materials were prepared through in situ generation of nanosilica within the epoxy resin. The stimuli utilized for the shape memory behavior was temperature, exploiting the visco-elastic behavior of the epoxy resin. The results contribute to improved understanding of this type of shape memory materials.

3. A core–shell structure of polyaniline coated protonic titanate nanobelt composites for both Cr(VI) and humic acid removal, Tao Wen, Qiaohui Fan, Xiaoli Tan, Yuantao Chen, Changlun Chen, Anwu Xu, Xiangke Wang, Polym. Chem., 2016, 7, 785-794.

Core-shell polyaniline/hydrogen titanate nanobelt composites were prepared through in situ oxidative polymerisation which showed excellent absorption of Cr(VI) and humic acid for waste water treatment applications. The mechanisms of the Cr(VI) and humic acid removal were investigated as well as regeneration performance and reusability. The industrial implications on the composites appear promising; showing efficient and cost effective waste water treatment.


Dr. Fiona Hatton is a Web Writer for Polymer Chemistry. She is currently a postdoctoral researcher at KTH Royal Institute of Technology, Sweden, having completed her PhD in the Rannard group at the University of Liverpool, UK. Visit her webpage for more information.

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Paper of the month: Lights on! A significant photoenhancement effect on ATRP by ambient laboratory light

Zhang et. al. report a significant photoenhancement effect on classical ATRP and ATRP derivatives by ambient laboratory light.



Since the introduction of atom transfer radical polymerisation (ATRP) by Matyjaszewski and Sawamoto, a large diversity of other copper adjuncts have attracted considerable interest including activator regenerated by electron transfer (ARGET)-ATRP, activator generated by electron transfer (AGET)-ATRP, initiators for continuous activator regeneration (ICAR)-ATRP and single electron transfer living radical polymerisation (SET-LRP). Recently photoinduced copper radical polymerization has also drawn significant attention as CuBr2, typically referred to as deactivating species, can be reduced in situ generating the active CuBr species in the presence of UV or visible light. In this contribution, Jordan and co-workers investigated on whether the typical laboratory light would have any considerable impact on standard ATRP reactions. Interestingly, the vast majority of the ATRP techniques (with the exception of ARGET-ATRP) demonstrated a remarkable photoenhancement effect by ambient light, originated from common fluorescent lamps. It was observed that when less copper complex is utilized for the polymerizations, a stronger influence of the ambient light in the monomer conversion is evident and this effect was significant even in the presence of additional reducing agents. As a general rule, it was concluded that the slower the polymerization is, the more pronounced the effect of the ambient laboratory light can be. As it was proved that it makes a difference if one is performing an ATRP reaction with the hoods on and off, the effect of the laboratory light on the polymerization can no longer be neglected and the authors encourage the report of the light conditions in typical ATRP experiments in order to ensure the reproducibility. 

Tips/comments directly from the authors:

Comments:
In this study, we provide conclusive evidence that common laboratory light especially originating from fluorescence lamps has a significant impact on ATRP. This is most probably one main reason why reproducibility of ATRP reactions are not as it should be which impairs further development of controlled radical polymerization techniques. As shown, the impact of light is different for the different ATRP recipes and will also strongly vary with the:

1. Type of complex formed regarding the metal and the ligands;
2. Quantity/concentration of metal complex formed and surely;
3. Type of illumination (natural light, type of fluorescent lamps installed in the laboratory and light intensity in the reaction vial). Strong influence were found for the “hood light illumination” (see Fig. 1 for description and Fig. 2 for experimental data) which was also very surprising for us. We therefore suggest to check the type of light bulbs/source of light, consider their emission spectra and resulting intensity at the location of the reaction and possibly provide these details in the experimental section to ensure reproducibility.

Tips:
1. The various metal complexes used in ATRP are most probably photosensitive but to a different extent. Thus, the influence of laboratory light will vary.
2. Perform the ATRP reactions always under the same light settings with the same light source and provide details (type of lamp, light intensity at each location of the reaction) in the experimental section.
3. Especially modern fluorescent lamps have a higher emission in the blue range and thus may have a stronger/other influence upon conversion/kinetics of the ATRP. Check the emission spectra of the lamps installed in the laboratory and especially in the chemical fume hoods.

Lights on! A significant photoenhancement effect on ATRP by ambient laboratory light by Tao Zhang Dan Gieseler and Rainer Jordan, Polym. Chem., 2016, 7, 775-779


Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently an Elings Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB).Visit her webpage for more information.

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Top 10 most-read Polymer Chemistry articles – Q4 2015

This month sees the following articles in Polymer Chemistry that are in the top 10 most accessed from October – December:

Lignocellulosic biomass: a sustainable platform for the production of bio-based chemicals and polymers
Furkan H. Isikgor and C. Remzi Becer
Polym. Chem., 2015,6, 4497-4559
DOI: 10.1039/C5PY00263J

Thiol-ene “click” reactions and recent applications in polymer and materials synthesis
Andrew B. Lowe
Polym. Chem., 2010,1, 17-36
DOI: 10.1039/B9PY00216B

Supramolecular hydrogels assembled from nonionic poly(ethylene glycol)-b-polypeptide diblocks containing OEGylated poly-l-glutamate
Shusheng Zhang, Wenxin Fu and Zhibo Li
Polym. Chem., 2014,5, 3346-3351
DOI: 10.1039/C4PY00016A

Thiol–ene “click” reactions and recent applications in polymer and materials synthesis: a first update
Andrew B. Lowe
Polym. Chem., 2014,5, 4820-4870
DOI: 10.1039/C4PY00339J

Investigation into thiol-(meth)acrylate Michael addition reactions using amine and phosphine catalysts
Guang-Zhao Li, Rajan K. Randev, Alexander H. Soeriyadi, Gregory Rees, Cyrille Boyer, Zhen Tong, Thomas P. Davis, C. Remzi Becer and David M. Haddleton
Polym. Chem., 2010,1, 1196-1204
DOI: 10.1039/C0PY00100G

Oxidant-induced dopamine polymerization for multifunctional coatings
Qiang Wei, Fulong Zhang, Jie Li, Beijia Li and Changsheng Zhao
Polym. Chem., 2010,1, 1430-1433
DOI: 10.1039/C0PY00215A

Scalable synthesis and derivation of functional polyesters bearing ene and epoxide side chains
Yunfeng Yan and Daniel J. Siegwart
Polym. Chem., 2014,5, 1362-1371
DOI: 10.1039/C3PY01474F

End group removal and modification of RAFT polymers
Helen Willcock and Rachel K. O’Reilly
Polym. Chem., 2010,1, 149-157
DOI: 10.1039/B9PY00340A

The power of light in polymer science: photochemical processes to manipulate polymer formation, structure, and properties
Shunsuke Chatani, Christopher J. Kloxin and Christopher N. Bowman
Polym. Chem., 2014,5, 2187-2201
DOI: 10.1039/C3PY01334K

Bringing d-limonene to the scene of bio-based thermoset coatings via free-radical thiol–ene chemistry: macromonomer synthesis, UV-curing and thermo-mechanical characterization
Mauro Claudino, Jeanne-Marie Mathevet, Mats Jonsson and Mats Johansson
Polym. Chem., 2014,5, 3245-3260
DOI: 10.1039/C3PY01302B

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

Fancy submitting an article to Polymer Chemistry? Then why not submit to us today!

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Focus on: Polymers in Catalysis

This month, focussing on polymers in catalysis, we look at three articles where catalytic activity has been inferred to a polymer chain through functionalisation of the polymer, or through using the polymer as a support for another catalyst.

In the body, reactions are usually catalysed by enzymes. Mimicking enzyme activity with synthetic polymers has been investigated for several types of enzymes, here, in the first article a polymer was prepared mimicking the activity of S-adenosyl methionine synthetase.

Transition metal catalysis is widely used in the preparation of polymers as well as organic molecules, one major disadvantage is the removal of the catalyst after completion of the reaction. The second article describes a proposed solution to this problem through a thermoresponsive catalytic polymer. In the third article a porous polymer support containing in situ generated gold nanoparticles highlights another route to circumvent the issues with removal of catalytic residues, by utilising solid supported catalysts.

ToC image for article

1. Synthetic polymeric variant of S-adenosyl methionine synthetase, Lakshmi Priya Datta, Binoy Maiti, Priyadarsi De, Polym. Chem., 2015, 6, 7796-7800.

The authors describe the synthesis of a polymer via RAFT and subsequent functionalisation with methionine moeities which mimicked the activity of the enzyme S-adenosyl methionine synthetase. Methionine plays major roles in the biosynthesis of proteins and DNA methylation. The resulting polymer was shown to methylate cytosine in the absence of a methyltransferase enzyme, highlighting the enzyme-like activity of the polymer.

2. A thermoresponsive polymer supporter for concerted catalysis of ferrocene with a ruthenium catalyst in living radical polymerization: high activity and efficient removal of metal residues, Kojiro Fujimura, Makoto Ouchi, Mitsuo Sawamoto, Polym. Chem., 2015, 6, 7821-7826.

With the aim to achieve the efficient removal of metal residues from ruthenium-ferrocene concerted catalysed living radical polymerisation, a thermoresponsive polymer support was prepared containing ruthenium as a catalyst and ferrocene as a cocatalyst. This was used to catalyse the polymerisation of MMA in toluene, and subsequent aqueous washing resulted in the almost quantitative removal of Ru (99.8% removal) and Fe (98.5% removal), showing promise for practical applications.

3. “Clickable” thiol-functionalized nanoporous polymers: from their synthesis to further adsorption of gold nanoparticles and subsequent use as efficient catalytic supports, Benjamin Le Droumaguet, Romain Poupart, Daniel Grande, Polym. Chem., 2015, 6, 8105-8111.

A porous polymeric material was prepared through a channel die processing technique, consisting of PS-b-PLA, where the two blocks were connected through a disulphide linkage. After removal of the PLA block, the remaining thiol groups were utilised in both post-modification “click” reaction and in situ gold nanoparticle (GNP) generation. The porous polymer GNP hybrid catalysed the reduction of 4-nitrophenol to 4-aminophenol with a yield of 68%, and retained this efficiency over 5 runs.


Dr. Fiona Hatton is a Web Writer for Polymer Chemistry. She is currently a postdoctoral researcher at KTH Royal Institute of Technology, Sweden, having completed her PhD in the Rannard group at the University of Liverpool, UK. Visit her webpage for more information.

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Paper of the month: Solvent-free mechanochemical synthesis of a bicyclononyne tosylate: a fast route towards bioorthogonal clickable poly(2-oxazoline)s

Glassner et. al. report a new solvent-free mechanochemical synthesis of a bicyclononyne tosylate.

The strain promoted azide-alkyne cycloaddition of cyclooctynes (SPAAC) is a popular bioorthogonal reaction that enables the tracking of biomacromolecules in living systems. Among the various cylooctynes that have been developed for SPAAC reactions, derivatives of bicyclo[6.1.0]non-4-yne (BCN) have attracted considerable interest for a number of reasons including their low hydrophobicity and ability to undergo fast cycloadditions not only with azides but also with nitrones. At the same time, poly(2-oxazoline)s (PAOx) represent a promising class of polymers for biomedical applications that can easily incorporate clickable end-groups by employing functional initiators or terminators. In this paper, Hoogenboom and co-workers present the first mechanochemical synthesis of a BCN tosylate (BCN-OTs) initiator via solvent-free reaction conditions utilizing high speed vibration milling instead of manual grinding. The BCN-OTs was subsequently used for the cationic ring opening polymerization (CROP) of 2-ethyl-2-oxazoline (EtOx) yielding a well-defined polymer and demonstrating controlled/living polymerization features such as narrow molecular weight distributions and high chain end fidelity. This represents a rapid route to prepare defined BCN functionalized PEtOx that can be used for bioorthogonal strain-promoted conjugation reactions. This was successfully demonstrated for the synthesis of a PS-b-PEtOx copolymer and a PEtOx-protein conjugate. As such, BCN-OTs may find potential applications as intermediate in the synthesis of functional BCN derivatives and BCN-PAOx. In addition, the ball-milling methodology utilized for this study is a promising tool for the synthesis of other unstable/highly reactive tosylates.

Tips/comments directly from the authors:

1)    KOH and K2CO3 should be finely grounded and dried in a vacuum oven prior to use.

2)    During the synthesis of BCN-OTs, removal of solvents has to be performed at ambient temperature (turn of the heating bath of the rotary evaporator).

3)    BCN-OTs has to be used immediately for the next step because of its limited stability at ambient conditions.

Solvent-free mechanochemical synthesis of a bicyclononyne tosylate: a fast route towards bioorthogonal clickable poly(2-oxazoline)s by M. Glassner, S. Maji, V. de la Rosa, N. Vanparijs,  K. Ryskulova, B. De Geest and R. Hoogenboom, Polym. Chem., 2015, 6, 8354-8359


Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Warwick (UK)/ Monash (Australia) research fellow working under the Monash Alliance. Visit http://haddleton.org/group-members for more information.

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Editorial Board’s Top Picks: Emily Pentzer

Emily Pentzer is an Associate Editor for Polymer Chemistry and an Assistant Professor of Chemistry at Case Western Reserve University, USA. Her research addresses application-based materials problems in the areas of energy harvesting, management, and storage. She uses synthetic chemistry to tailor molecular design and control self-assembly for the preparation and study of novel conductive materials with controlled domain sizes and interfaces.

You can find all Editorial Board’s Top Picks papers in our web collection.



Focus on PAH building blocks for electronically active and porous polymers (Associate Editor: Prof Emily Pentzer Case Western Reserve University, USA)

Polyaromatic hydrocarbons (PAHs) are attractive building blocks for electronically active and porous organic polymers. For these applications, the preparation and isolation of appropriate polymeric structures is needed to provide the desired properties. PAHs are typically incorporated into conjugated polymers by transition metal-catalyzed cross-coupling reactions, and their solubility and solution processability is ensured by substitution with alkyl groups; recent interest has focused on accessing reduced band gap structures.  Alternatively, for the preparation of porous organic polymers, the tendency of PAHs to aggregate through p-p interactions must be overcome, and alkyl groups are disadvantageous for gas adsorption/storage.  Recent advances in the design and synthesis of PAH-containing polymers have helped expand the usefulness of these heteroatom-free systems.

1. Anthanthrene as a large PAH building block for the synthesis of conjugated polymers
Antoine Lafleur-Lambert, Jean-Benoît Giguère and Jean-Francois Morin
Polym. Chem., 2015, 6, 4859-4863

Aromatic anthanthrene is readily available from the common dye vat orange 3 and can be used to prepare PAH-containing polymers.  Morin and coworkers report the preparation of a series of anthanthrene-based conjugated polymers. The anthanthrene unit has branched alkyl substituents to control solubility and was copolymerized with electron rich and electron poor aryl comonomers. The absorption spectra of these polymers range from 450 to 850 nm, depending on the constituent materials. The series of novel polymers all showed similar LUMO levels, and variation of the HOMO levels show no trends based on the comonomer identity. These results indicate that both the HOMO and the LUMO orbitals are located on the anthanthrene units, and are not heavily influenced by the comonomer identity.

2. Dicyclopenta[cd,jk]pyrene based acceptors in conjugated polymers
Sambasiva R. Bheemireddy and Kyle N. Plunkett
Polym. Chem., 2016, Advance Article

In this study, Plunkett and Bheemireddy report the use of the PAH dicyclopentapyrene, as an acceptor unit in conjugated polymers. This alkylated monomer was copolymerized with various electron donor comonomers including thiophene, bithiophene, and diethynyl benzene. In the thin film, these polymers show broad absorption profiles, from ~320-720 nm, corresponding to band gaps of ~1.7 eV. The identity of the comonomer with the PAH had little influence on the HOMO and LUMO levels, inconsistent with traditional donor-acceptor theory for reduced bandgap materials.  In fact, DFT calculations show the LUMO orbital distribution across the series is essentially unchanged and mostly located on the PAH unit (as expected), but surprisingly, the HOMO orbitals are also localized to the PAH unit for the thiophene and bithiophene polymers.

3. Di(naphthalen-2-yl)-1,2-diphenylethene-based conjugated polymers: aggregation-enhanced emission and explosive detection
Mengxia Gao, Yue Wu, Bin Chen, Bairong He, Han Nie, Tingyan Li, Fupeng Wu, Wenjun Zhou, Jian Zhou and Zujin Zhao
Polym. Chem., 2015, 6, 7641-7645

Di(naphthalene-2-yl)-1,2-diphenylethene is used as a building block by Zhao and coworkers to prepare fluorescent conjugated polymers which show aggregation induced emission. Addition of the poor solvent water to these polymers in THF causes them to aggregate and essentially turns on the fluorescence of the materials by preventing non-radiative excited state decay. DFT calculations show the HOMO and LUMO orbitals are significantly distributed over both comonomers, as well as the pendant naphthyl groups, indicating good intramolecular orbital overlap. These materials further show potential to detect explosives under aqueous conditions, as the fluorescence is quenched in the presence of picric acid.

4. Facile approach for preparing porous organic polymers through Bergman cyclization
Xian-Mei Zhang, Xuesong Ding, Aiguo Hu and Bao-Hang Han
Polym. Chem., 2015, 6, 4734-4741

The Bergman cyclization reaction was used to prepare microporous polymers from a triphenylene-based monomer that contains three ene-diyne moieties. This catalyst-free and thermally induced intramolecular cyclization produces three 1,4-benzene biradical per monomer that undergo intermolecular coupling to yield the porous polymer. Although the monomers themselves are planar, they link together in a non-planar fashion to give a porous, high surface area material. Han and coworkers then demonstrate that the novel micorporous polymers show high adsorption capacity for both hydrogen and carbon dioxide.

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Author of the Month: Prof. Dr. Ir. Bruno De Geest

Prof. Dr. Ir. Bruno De Geest graduated as Chemical Engineer in 2003 from Ghent University where he obtained his PhD in pharmaceutical sciences in 2006 on polyelectrolyte multilayer capsules for biomedical applications. For his PhD work he was awarded the graduate student award for pharmaceutical technology from the AAPS and the Andreas Deleenheer award from Ghent University. After 2 years of postdoctoral research at Utrecht University (The Netherlands) he returned to Ghent University at the Department of Pharmaceutics. From October 2012 onwards he is appointed as professor in Biopharmaceutical Technology.​​ Bruno De Geest has authored over 90 papers and his research group focus on the interface between materials science and life science with a particular interest in polymer chemistry, immunology and anticancer therapy.

Research website: http://brdegeest.wix.com/biopharmtech-degeest

What was your inspiration in becoming a chemist?

Chemistry offers a scientist the ability to create things using molecular scale building blocks, which appeared a very attractive concept to me. I’m a chemical engineer, thus not a hard core chemist by training. In 3rd year at university we had organic chemistry and later on polymers taught by Filip Du Prez who was then just appointed as professor. These courses awakened a strong interest in polymer chemistry and this interest still fuels the ambition of our lab to create new materials that could hopefully be of benefit for human medicine.

What was the motivation to write your Polymer Chemistry article?

One of the main focuses of our research group in nanoparticulate vaccine delivery. While endeavoring to attach vaccine antigens to polymeric nanoparticles we noticed that the efficiency of conjugating a polymer to a protein is disappointingly low. Therefore we decided at comparing head-to-head different conjugation chemistries based on functional RAFT chain transfer agents for grafting-onto protein conjugation. The message of our paper is twofold. Firstly it gives a guide to which chemistries as more efficient than others, at least for the specific cases we have tested. Secondly, it urges the need for more efficient polymer-protein conjugation strategies.

Why did you choose Polymer Chemistry to publish your work? (DOI: 10.1039/C4PY01224K)

Polymer Chemistry has high visibility in the chemical and materials science community and publishes a high number of papers dealing with topics on controlled radical polymerization and biomedical applications. In addition, the paper will be published as part of the upcoming Emerging Investigator Issue. I’m delighted to contribute especially with this paper as it is a signature paper for our current research line.

In which upcoming conferences may our readers meet you?

I’m attending the ACS Spring Meeting in Denver in March where together with Prof. Aaron Esser-Kahn we are organizing a POLY symposium on ‘Interacting with the immune system using polymeric systems’.

How do you spend your spare times?

I’m a keen cyclist and a love to ride with my race bike trough the Flemish Ardennes. This region south of Ghent towards the Walloon border is well known for the spring cycling classics and it is a privilege to ride the same roads and climb the same cobblestone hills as the pro cyclists.

Which profession would you choose if you were not a scientist?

I think I would have studied sciences anyway, but in stead of becoming a researcher I would like be a teacher. I have always enjoyed working together with young people.


Polymer-protein conjugation via a ‘grafting to’ approach – a comparative study of the performance of protein-reactive RAFT chain transfer agents

N. Vanparijs,   S. Maji,   B. Louage,   L. Voorhaar,   D. Laplace,   Q. Zhang,   Y. Shi,   W. E. Hennink,   R. Hoogenboom and   B. G. De Geest

Abstract: Efficient polymer-protein conjugation is a crucial step in the design of many therapeutic protein formulations including nanoscopic vaccine formulations, antibody-drug conjugates and to enhance the in vivo behaviour of proteins. Here we aimed at preparing well-defined polymers for conjugation to proteins by reversible addition–fragmentation chain transfer (RAFT) polymerization of both acrylates and methacrylamides with protein-reactive chain transfer agents (CTAs). These RAFT agents contain either a N-hydroxysuccinimide (NHS) or pentafluorophenyl (PFP) ester moiety that can be conjugated to lysine residues, and alternatively a maleimide (MAL) or pyridyl disulfide (PDS) moiety that can be conjugated to cysteine residues. Efficiency of the bioconjugation of these polymers to bovine and avian serum albumin was investigated as a function of stoichiometry, polymer molecular weight and the presence of reducing agents. A large molar excess of polymer was required to obtain an acceptable degree of protein conjugation. However, protein modification with N-succinimidyl-S-acetylthiopropionate (SATP) to introduce sulfhydryl groups onto primary amines, significantly increased conjugation efficiency with MAL- and PDS-containing polymers.


Cyrille Boyer is a guest web-writer for Polymer Chemistry. He is currently an associate professor and an ARC-Future Fellow in the School of Chemical Engineering, University of New South Wales (Australia) and deputy director of the Australian Centre for NanoMedicine.


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Focus on: Supramolecular Polymer Networks

Supramolecular interactions are defined as noncovalent bonds, including: hydrogen bonding, hydrophobic association, π-π stacking, transition metal complexation and ionic interactions. Supramolecular polymer networks consist of macromolecules which are interconnected through these transient noncovalent bonds. These materials are particularly interesting as they allow the capability of adaptive, self-healing materials which have mechanical properties that are dependent on the crosslinking interactions and the polymer topology. This month three articles are highlighted which demonstrate supramolecular interactions in polymer networks to give materials with interesting properties, such as self-healing, ductility and stimuli responsive changes in mechanical properties.

Graphical abstract from article (http://xlink.rsc.org/?doi=10.1039/C5PY01214G)

1. Self-healing, malleable and creep limiting materials using both supramolecular and reversible covalent linkages, Borui Zhang, Zachary A. Digby, Jacob A. Flum, Elizabeth M. Foster, Jessica L. Sparks, Dominik Konkolewicz, Polym. Chem., 2015, 6, 7368-7372.

The combination of supramolecular and reversible crosslinks was utilized to prepare materials with self-healing properties on different time scales. Supramolecular crosslinks between 2-ureido-4[1H]-pyrimidinone moieties gave dynamic crosslinks, whilst Diels-Alder coupling between a furan and a maleimide gave a considerably less dynamic linkage. The materials showed partial healing properties at room temperature and full healing at elevated temperatures.

2. Ultraductile, notch and stab resistant supramolecular hydrogels via host–guest interactions, Mei Tan, Yulin Cui, Aidi Zhu, Han Han, Mingyu Guo, Ming Jiang, Polym. Chem., 2015, 6, 7543-7549.

The authors describe the preparation of supramolecular hydrogels which were self-healing as well as extremely ductile and notch and stab resistant. The hydrogels were based on host-guest interactions between adamantane monomers and a low molecular weight polyfunctional cyclodextrin, prepared via free radical polymerisation. Native and healed gels gave similar tensile strain–stress trends, stretching to around 50 times their original lengths with almost complete recoverability.

3. Supramolecular polymer networks based on cucurbit[8]uril host–guest interactions as aqueous photo-rheological fluids, Cindy S. Y. Tan, Jesús del Barrio, Ji Liua, Oren A. Scherman, Polym. Chem., 2015, 6, 7652-7657.

Supramolecular polymer networks are reported based upon the host-guest interactions mediated by cucurbit[8]uril with naphthyl-functionalised hydroxyethyl cellulose, methyl viologen functional styrene copolymer and a photoisomerisable azobenzene imidazolium derivative. The resulting networks exhibited light-tunable rheological properties at low mass fractions (<0.75 wt%) showing a decrease in the zero-shear viscosity and viscoelastic moduli by UV irradiation.


Dr. Fiona Hatton is a Web Writer for Polymer Chemistry. She is currently a postdoctoral researcher at KTH Royal Institute of Technology, Sweden, having completed her PhD in the Rannard group at the University of Liverpool, UK. Visit her webpage for more information.

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Paper of the month: Synthesis and characterization of TEMPO- and viologen-polymers for water-based redox-flow batteries

Janoschka et al. report TEMPO and viologen containing polymers for water-based redox-flow batteries.


Redox-flow batteries (RFBs) provide an inexpensive, safe and long lasting approach towards the development of stationary large-scale energy storage. Typically, RFBs employ redox- active materials that dissolve in either aqueous or organic solutions, although many of the existing systems challenge the chemical stability of installed battery components and impose a safety risk. Vanadium salts in sulphuric acid consist the most thoroughly studied system and when aqueous solutions are additionally employed further advantages can be achieved including low corrosivity, high safety and affordable size-exclusion membranes. In this current contribution, Schubert and co-workers present the screening of two series of redox-active polymers that can potentially find application in water-based polymer redox-flow batteries (pRFBs). The rheological and electrochemical properties of both viologen and TEMPO containing polymers have been investigated in details. The viologen-homopolymer poly(1-methyl-1’-(4-vinylbenzyl)-[4,4’-bipyridine]-1,1’-diium dichloride) was found to exhibit good solubility in water (even in the reduced state) and a redox potential of -0.4 V (vs Ag/AgCl), demonstrating its suitability as an anode material. On the other hand, the TEMPO-polymer showed reduced solubility in aqueous solution and thus requiring a solubilizing comonomer. Although poly(ethyleneglycol)-based comonomers and methacrylamide were subsequently tested, the unfavourable LCST and the requirement of high mole fractions respectively led to the investigating of a third alternative. Pleasingly, poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl-co-2-(methacryloyloxy)-N,N,N-trimethylethane ammonium chloride) proved to be a suitable cathode material for pRFBs when a choline moiety was used as the solubilizing unit. In summary, the presented work paves the way for the production of economical energy storage devices that are safe, metal free and utilise all-organic raw materials.

Tips/comments directly from the authors:

1. It should be noted that the redox-active polymer solutions can be used straight from the reaction vessel and without further purification for the designated application in pRFBs.

2. The TEMPO-polymers are excellent surfactants and prone to foam formation. The authors highly encourage the reader to come up with ideas for potential applications of this redox-active, radical-bearing surfactant.

3. When preparing polymers for pRFBs the molar mass of the polymer should be tailored in order to fit the size-exclusion membrane (dialysis membrane) used in the battery. The dispersity Đ should be low to ensure good rheological properties.

Synthesis and characterization of TEMPO- and viologen-polymers for water-based redox-flow batteries, by T. Janoschka, S. Morgenstern, H. Hiller, C. Friebe, K. Wolkersdörfer, B. Häupler, M.D. Hager and U.S. Schubert, Polym.Chem., 2015, 6, 7801-7811


Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently a Warwick (UK)/ Monash (Australia) research fellow working under the Monash Alliance. Visit http://haddleton.org/group-members for more information.

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2016 Polymer Chemistry Lectureship is now open!

Do you know an early-career researcher who deserves recognition for their contribution to the polymer chemistry field?

Now is your chance to put them forward for the accolade they deserve.

Polymer Chemistry is pleased to announce that nominations are now being accepted for its 2016 Lectureship award. This annual award was established in 2015 to honour an early-stage career scientist who has made a significant contribution to the polymer chemistry field.

Previous winners

2015 – Richard Hoogenboom, Ghent University, Belgium

Qualification

To be eligible for the Polymer Chemistry Lectureship, the candidate should be in the earlier stages of their scientific career, typically within 15 years of attaining their doctorate or equivalent degree, and will have made a significant contribution to the field.

Description

The recipient of the award will be asked to present a lecture three times, one of which will be located in the home country of the recipient. The Polymer Chemistry Editorial Office will provide the sum of £1000 to the recipient for travel and accommodation costs.

The recipient will be presented with the award at one of the three award lectures. They will also be asked to contribute a lead article to the journal and will have their work showcased on the back cover of the issue in which their article is published.

Selection

The recipient of the award will be selected and endorsed by the Polymer Chemistry Editorial Board.

Nominations

Those wishing to make a nomination should send details of the nominee, including a brief C.V. (no longer than 2 pages A4) together with a letter (no longer than 2 pages A4) supporting the nomination, to the Polymer Chemistry Editorial Office by 29th January 2016. Self-nomination is not permitted.

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