Polymer Chemistry Blog

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

23 Dec 2015

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

04 Dec 2015

By Alice Jensen, Development Editor.

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

04 Dec 2015

By Cyrille Boyer.

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 3^rd 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

02 Dec 2015

By Fiona Hatton.

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

25 Nov 2015

By Athina Anastasaki, Web Writer.

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

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2016 Polymer Chemistry Lectureship is now open!

03 Nov 2015

By Pete Livermore, Deputy Editor.

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 29^th January 2016. Self-nomination is not permitted.

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Focus on: Polymers from Renewable Resources

29 Oct 2015

By Fiona Hatton.

With increasing demands upon our planet’s resources, more and more research efforts are focussing on preparing new materials from renewable resources. Especially considering the global plastic production (299 million tonnes in 2013), new routes towards renewable polymers are ever more desirable. Renewable polymers can generally be classified into the following three groups: naturally occurring polymers such as polysaccharides and proteins, polymers prepared by microbial fermentation and polymers synthesised from bioderived monomers. This month, focussing on polymers from renewable resources, we take look at three articles which utilize renewable plant-derived monomers to synthesise various polyesters. The plant-derived monomers described are based on the following compounds: erucic acid, commonly found in rapeseed oil, eugenol which is present in clove oil and δ-decalactone which can be extracted from Cryptocarya massoia.

1. Thermoplastic polyester elastomers based on long-chain crystallizable aliphatic hard segments, Florian Stempfle, Brigitta Schemmer, Anna-Lena Oechsle, Stefan Mecking, Polym. Chem., 2015, 6, 7133-7137.

Thermoplastic polyesters were prepared via polycondensation with a plant-oil based long chain (C23) α,ω-dicarboxylic acid and the corresponding diol comprising the hard segments, and poly(tetramethylene glycol) (PTMG) or carbohydrate-based poly(trimethylene glycol) (PPDO) soft segments. Physical crosslinking was achieved through crystallization of the long aliphatic segments, resulting in enhanced thermal properties when compared to the C12 analogues.

2. Synthesis and properties of polyesters derived from renewable eugenol and α,ω-diols via a continuous overheating method, Keling Hu, Dongping Zhao, Guolin Wu, Jianbiao Ma, Polym. Chem., 2015, 6, 7138-7148.

Aromatic monomers derived from eugenol were synthesised utilizing “click” chemistry and a subsequent Williamson ether synthesis. They were subsequently polymerised with various α,ω-diols via a continuous overheating method across the transesterification stage to form polyester thermoplastics. The Young’s modulus and ultimate strength of the resulting materials was not particularly high although they exhibited excellent ductility.

3. New biomaterials from renewable resources – amphiphilic block copolymers from δ-decalactone, Kuldeep K. Bansal, Deepak Kakde, Laura Purdie, Derek J. Irvine, Steven M. Howdle, Giuseppe Mantovani, Cameron Alexander, Polym. Chem., 2015, 6, 7196-7210.

Various polymers and copolymers were synthesized from the low-cost and easily-accessible renewable monomer δ-decalactone, which is an FDA approved flavouring agent. Amphiphilic copolymers were shown to self-assemble into micelles which were biodegradable and showed low toxicity in vitro. The micelles enabled sustained release of a model drug compound over 8 days, highlighting the possible biomedical application of these degradable δ-decalactone copolymers.

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Paper of the month: Micro-patterned polymer brushes by a combination of photolithography and interface-mediated RAFT polymerization for DNA hybridization

27 Oct 2015

By Athina Anastasaki, Web Writer.

Cimen et al. report the fabrication of micro-patterned polymer brushes for DNA attachment and subsequent hybridization.

The covalent immobilization of DNA probes has been extensively studied over the past ten years. Among others approaches, the binding of protected organic molecules on the silicon surfaces followed by the deprotection of the attached groups is perhaps one of the most popular routes. However, the harsh conditions typically utilized for the deprotection have a detrimental effect on the quality of the surface and as such alternative approaches have also been exploited including growth of brushes from a range of substrates.

In this paper, Caykara and Cimen investigated the micro-patterning of poly(6-azidohexylmethacrylate) [poly(AHMA)] brushes via a combination of photolithography and interface-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization for DNA hybridization. Upon immobilization of the RAFT agent on the Si surface followed by the attachment of 2-(2-carboxyethylsulfanylthiocarbonylsulfanyl)propionic acid (TTC5) (photoresist-coated substrate), poly(AHMA) brushes were grown via interface-mediated RAFT polymerization. AFM was used to determine the thickness of the polymer brush which was found to approach the average thickness of a uniform (AHMA) brush film. Propargylamine was subsequently used to functionalize the azide groups of poly(AHMA) via a click reaction as confirmed by X-ray photoelectron spectroscopy (XPS). The micro-patterned poly(AHMA) brushes with amine pendant groups were then chemically modified in order to function as selective adsorption sites for DNA hybridization. In order to form a non-active background, the probe DNA molecules were successfully coupled onto the micro-patterned poly(AHMA) brushes, as shown by AFM and ellipsometry. The probe DNA modified surfaces were subsequently incubated in the presence of complementary DNA and the successful hybridization of complementary DNA molecules on the micro-patterned poly(AHMA) was confirmed by confocal microscopy and AFM. This simplified and straightforward approach provides a platform for the immobilization of complicated structures on silicon surfaces with potential applications in biosensing and the production of novel materials.

Tips/comments directly from the authors:

1. 11-amino-1-undecene (AUD) cannot be attached directly to the hydrogen terminated silicon surface because of the free amino functional groups. So, in this study, the amino group was protected by the t-butyloxycarbonyl group (t-BOC). The protection reaction is easily performed but during the vacuum purification of the product, control of the temperature and pressure is of vital importance. Gentle heating and constant vacuum pressure must be carried out to prevent the decomposition of t-BOC-AUD.

2. Si-H surface can be easily oxidized at atmosphere. So, rinsing of Si-H surface and coating of t-BOC-AUD must be performed immadiately in a glove box.

3. In the photolithography process, coating of the photoresist was carried out under yellow light. Until removing of the unexposed areas, the surfaces must be kept under safe light.

4. To avoid loss of resolution during the UV exposure, obtaining a thin and homogenous coating on the silicon surface is extremely important. Therefore, the silicon wafers should be cleaved into uniform square or rectangle pieces before the lithography process and the surfaces must be modified homogeneously.

Micro-patterned polymer brushes by a combination of photolithography and interface-mediated RAFT polymerization for DNA hybridization, by D. Cimen and T. Caykara, Polym. Chem., 2015, 6, 6812-6818

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Editorial Board’s Top Picks: Bin Liu

26 Oct 2015

By Alice Jensen, Development Editor.

Bin Liu is an Associate Editor for Polymer Chemistry and Dean’s Chair Professor at the Department of Chemical & Biomolecular Engineering, National University of Singapore (NUS), Singapore. Her research focuses on the development of organic functional materials and the exploration of their applications in sensing, imaging and solar cells.

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

Focus on Responsive Polymers (Associate Editor: Prof Bin Liu, NUS, Singapore)

1. Voltage-responsive micelles based on the assembly of two biocompatible homopolymers
Liao Peng, Anchao Feng, Huijuan Zhang, Hong Wang, Chunmei Jian, Bowen Liu, Weiping Gao and Jinying Yuan. Polym. Chem. 2014, 5, 1751-1759.

Effective drug delivery and drug release systems in vivo generally require drug carriers to specifically respond to external stimuli. J. Yuan and coworkers from Tsinghua University (China) have synthesized voltage-responsive biocompatible micelles based on two host and guest molecules, poly(ethylene glycol) homopolymer modified with beta-CD (PEG-beta-CD) and the poly(L-lactide) homopolymer modified with Fc (PLLA-Fc). A reversible assembly- disassembly transition of this micellar system was realized through electrochemical control and voltage-controlled drug release was also successfully demonstrated.

2. Reversibly crosslinked thermo- and redox-responsive nanogels for controlled drug release
Ji Liu, Christophe Detrembleur, Marie Hurtgen, Antoine Debuigne, Marie-Claire De Pauw-Gillet, Stéphane Mornet, Etienne Duguet and Christine Jérôme. Polym. Chem. 2014, 5, 77-88.

Micelle assembly using crosslinking could minimize the premature drug delivery usually observed in physically assembled micelles. C. Detrembleur, C. Jérôme and coworkers from the University of Liege (Belgium) have prepared reversibly crosslinked poly(vinyl alcohol)-b-poly(N-vinylcaprolactam) PVOH-b-PNVCL nanogel by using a redox-responsive crosslinking agent, and demonstrate its effectiveness in thermo- and redox responsive drug delivery using Nile red (NR) as a hydrophobic drug model.

3. Light-responsive linear-dendritic amphiphilles and their nanomedicines for NIR-triggered drug release
Lin Sun, Bangshang Zhu, Yue Su and Chang-Ming Dong. Polym. Chem. 2014, 5, 1605-1613.

Development of new-generation polymeric nanomedicines with spatiotemporal and/or on-demand drug-release behaviour is in high demand for clinical therapies and personalized medicines. Taking advantage of the stealthy properties of biocompatible PEO and the multivalent periphery properties of dendritic polymers, C. M. Dong and coworkers at Shanghai Jiao Tong University in China, have reported the synthesis of both ultraviolet (UV) and near-infrared (NIR) light-responsive linear-dendritic amphiphiles, which have been successfully used for light-triggered drug release.

Review article

1. Multi-stimuli responsive polymers – the all-in-one talents
Philipp Schattling, Florian D. Jochum and Patrick Theato. Polym. Chem. 2014, 5, 25-36.

The manifold applications of in stimuli-responsive polymers have spurred increasing research interest in the field. The combination of multiple responsive groups into one polymer may produce a multi-functional polymer which exhibits a multifaceted change of material properties when applying one or more external stimuli. In this review article, P. Theato et. al. at University Hamburg in Germany, summarised recent developments in the area of multi-stimuli responsive polymers with more than two responsive groups and highlighted a number of fascinating examples. These multi-responsive materials will open up opportunities for development of both life science and information technology.

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Polymer Chemistry Blog

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

Editorial Board’s Top Picks: Emily Pentzer

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

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

Focus on: Supramolecular Polymer Networks

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

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?

Focus on: Polymers from Renewable Resources

Paper of the month: Micro-patterned polymer brushes by a combination of photolithography and interface-mediated RAFT polymerization for DNA hybridization

Editorial Board’s Top Picks: Bin Liu

Top 10 most-read Polymer Chemistry articles – Q3 2015

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