Polymer Chemistry Blog

Author of the Month: Dr. Andreas Walther

10 Jun 2015

Dr. Andreas Walther graduated from Bayreuth University in Germany in 2008 with a PhD focusing on the self-assembly behaviour and applications of Janus particles and other soft, complex colloids. After a postdoctoral stay with a focus on biomimetic hybrid materials at Aalto University (Helsinki, Finland), he returned to Germany and established his independent research group at the DWI – Leibniz Institute for Interactive Materials in Aachen. His research interests concentrate on developing and understanding hierarchical self-assembly concepts inside and outside equilibrium, and on utilising and connecting such processes to soft materials research – often following bioinspired design principles. Andreas has published more than 90 papers and has recently been awarded the Bayer Early Excellence in Science Award (for Materials) and the Reimund Stadler Young Investigator Award of the German Chemical Society.

What was your inspiration in becoming a chemist?

I believe one of the big chemical companies is responsible for attracting me to chemistry by sending a “polymer science kit”, containing foams, resins and a toolkit to prepare Nylon fibres, to my senior class when I was still back in secondary school. Even nowadays, I still think that the classical experiment of pulling a polyamide fibre from the interface of oil/water monomer mixtures is one of the most intriguing and instructive experiments in a polymer class.

What was the motivation to write your Polymer Chemistry article?

Our main interest lies in developing self-assembly concepts to create new soft materials, for which we heavily rely on very well defined building blocks with tailored functionalities and interactions. Modern polymer chemistry provides us with the tools to make desirable building blocks with relative ease of synthesis. In this case we were interested in a straightforward way to modify the surfaces of colloidal particles to provide us with very specific biorecognition units, while at the same time rejecting all non-specific protein adhesion. Interestingly enough, despite all the common knowledge about the protein-repellent properties of polyethylene glycol (PEG) coatings, we could only find a very small amount of systematic studies discussing how for instance the architecture and composition of adsorbed PEG-based block copolymers influence protein repellency. So we went through a systematic study and optimised the building blocks to provide us with the required features for our future work. The underlying structure/property relationships at this point will be interesting for other researchers working on surface modification, biorecognition and protein-fouling.

Why did you choose Polymer Chemistry to publish your work?

Polymer Chemistry strives for high-level and interdisciplinary scientific contributions covering all modern aspects of polymer chemistry. We felt it to be the right place to achieve highest reach and recognition in the field.

In which upcoming conferences may our readers meet you?

European Polymer Federation Meeting, 21-26 June 2015, at Dresden, Germany.

How do you spend your spare time?

Keeping the work/life balance is probably one of the hardest challenges when working in science. I very much enjoy cooking to take my mind off stressful events, and I enjoy travelling to see new places and meet interesting people.

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

Indeed a very good question, I would probably follow another creative passion. Best-case scenario would then be running a restaurant in a picturesque place.

Combining the incompatible: Block copolymers consecutively displaying activated esters and amines and their use as protein-repellent surface modifiers with multivalent biorecognition

Daniel Hoenders, Thomas Tigges and Andreas Walther

We present the facile synthesis and orthogonal functionalization of diblock copolymers containing two mutually incompatible segments, i.e. primary amines and activated esters, that are displayed chronologically and synthesized by consecutive radical addition fragmentation transfer polymerization (RAFT) of suitably modified monomers. Post-polymerization modification of the active ester moieties with functionalized triethylene glycol derivatives (TEG-NH₂/BiotinTEG-NH₂) furnishes a protein-repellent block with specific biorecognition, and the activation of the amine groups via deprotection results in newly reactive primary amines. We subsequently use these amines as an anchoring layer for the coating of aldehyde-functionalized polystyrene (PS) colloids and demonstrate tight adhesion and enhanced protein-repellent characteristics combined with specific and multivalent biorecognition of avidin as a function of block ratios. Our strategy demonstrates a viable approach for orthogonal combination of widely needed, but mutually incompatible, functional groups into complex polymer architectures.

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), deputy director of the Australian Centre for NanoMedicine and member of Centre for Advanced Macromolecular Design.

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Recent Appointees in Materials Science 2015 Conference (RAMS2015)

28 May 2015

By Katie Nicholson, Development Editor.

We are delighted to announce that the Recent Appointees in Materials Science 2015 Conference (RAMS2015) will be held at the University of Warwick on 16-17^th September 2015.

Deadlines and dates

Registration will open shortly so be sure to sign up to this essential meeting before 1^st September 2015! The cost of registration is £125 for accommodation and meals, including the conference banquet at Warwick Castle. A reduced rate of £70 is offered for those not requiring accommodation.

Abstract submissions are now being accepted for oral and poster presentation but make sure you submit your abstracts by the deadline on 30^th June 2015.

Bursaries

A small number of bursaries are available for those with limited travel budgets and will be assessed on an individual basis. Enquire about bursaries here.

Keynote speakers

Biomaterials Science Advisory Board member Andrew Dove (University of Warwick) will be speaking along with other keynote speakers Aron Walsh (University of Bath) and Mary Ryan (Imperial College London). View the full list of invited speakers here.

For full details visit the RAMS2015 website. We hope you can join the materials science community for this fantastic event.

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Paper of the Month: Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization

26 May 2015

By Pete Livermore, Deputy Editor.

Truong et al. describe the synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerisation.

aper of the month: Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization

Ultra high molecular weight (UHMW) polymers have always been an ambitious target for synthetic polymer chemists. However, synthesising these materials using controlled radical polymerisation is challenging due to high levels of bimolecular termination and chain transfer to monomer that impede the growth of polymer chains. Monomers with higher propagation rate coefficient (k_p) such as acrylamides and acrylates (and even methacrylates) have been successfully polymerised up to 10⁶ g mol^-1 but lower k_p monomers (e.g. styrene) typically present broad molecular weight distributions when high molecular weight (e.g. 10⁶ g mol^-1) is targeted.

Truong et al. envisaged that a high polymerisation rate for the polymer chains would be required in order to produce well-defined UHMW polystyrene, whilst at the same time termination and side reactions would need to be minimised. The authors addressed this by employing the use of novel macromolecular chain transfer agents (CTA) in reversible addition fragmentation chain transfer polymerisation (RAFT)-mediated emulsion polymerisation. N-hydroxyethyl acrylamide (HEAA) and poly(ethylene glycol) methyl ether acrylate (PEGA) were copolymerised under judiciously selected reaction conditions to identify the most effective macrostabiliser for the emulsion polymerisation. The choice of these monomers proved crucial for the polymerisation, with PEGA conferring excellent antifouling characteristics while HEAA improves the water solubility of the macromolecular CTA and reduces partitioning of the macro-stabilisers within the styrene droplets and/or at the water/droplet interfaces. Under carefully optimised conditions, UHMW polystyrene of 10⁶ g mol^-1 could be obtained with relatively low dispersity values (<1.4) and unimodal molecular weight distributions even at near-quantitative conversions (>90%). Moreover, UV-Vis analysis confirmed the presence of the CTA, further suggesting that the reversible-deactivation radical polymerisation mechanism remained operative even to this very high conversion and molecular weight. Another interesting feature of this work is the linear relationship between particle size and molecular weight in this system, which seems to depart from the packing parameter theory, typically used to explain morphology transformations during emulsion or aqueous dispersion polymerisations. TEM analysis in all samples revealed uniformly spherical nanoparticles, even when the chain length of the polystyrene core was well above the threshold for the worm and vesicle formation. These experiments suggest that the packing parameter theory cannot be applied for all polymerisation-induced self-assembly systems and that further theoretical models are potentially required to fully understand the equilibrium morphology of soft nanoparticles.

In short, this article has overcome a longstanding challenge in the synthesis of UHMW polymers and created a new nanomaterial which offers great potential in numerous applications.

Summary points from the authors:

4,4′-Azobis(4-cyanopentanoic acid (ACPA) (free radical initiator) completely dissolves in water only after stirring for about 30 min. The stock ACPA solution should be made up fresh and not be stored for later use.
To avoid the loss of styrene monomer (by evaporation) during polymerisation, there is no need to keep the emulsion polymerisation under the continuous flow of nitrogen.
Samples prepared for dynamic light scattering measurements were not filtered, and as such filtration might enable a further reduction in the particle size distribution.
The molar ratio of HEAA to PEGA in the macromolecular CTAs was optimised at 1 to 1. A higher molar ratio of HEAA to PEGA results in aggregation when targeting ultra-high molecular weight polystyrene. A lower molar ratio of HEAA to PEGA results in a higher portion of macromolecular CTAs partitioning within the styrene droplets.

Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization by Nghia P. Truong, Marion V. Dussert, Michael R. Whittaker, John F. Quinn and Thomas P. Davis, Polym. Chem., 2015, 6, 3865-3874

Dr. Athina Anastasaki is a is a guest web-writer for Polymer Chemistry. She is currently a Warwick University (UK) and Monash University (Australia) research fellow working under the Monash Alliance. Visit the Haddleton group’s website for more information.

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Author of the Month: Prof. Makoto Obata

18 May 2015

By Cyrille Boyer.

Professor Makoto Obata received his Ph.D. degree in polymer chemistry from Hokkaido University, Japan in 1999. In 2000, he joined Professor Percec’s group at the University of Pennsylvania as a postdoctoral fellow. After one and a half years, he joined the faculty of Nara Women’s University from 2001 to 2009. In 2009, he moved to the University of Yamanashi, where he is now an Associate Professor of Applied Chemistry. His research area is the synthetic chemistry of functional polymers containing carbohydrates and dyes.

Take a look at Professor Makoto Obata research group’s website (please select translate for English).

What was your inspiration in becoming a chemist?

The training of my scientific expertise started at Asahikawa National College of Technology, Hokkaido, Japan, when I was 15 years old. I had an impressive supervisor at the college, and I was enthusiastic about studying my first research project on the synthesis of polymers bearing crown-ether for lithium ion capturing. After this experience, I was enchanted with the design and synthesis of new materials, especially organic materials.

What was the motivation to write your Polymer Chemistry article?

I started my career in Professor Yano’s laboratory at Nara Women’s University, Japan. His research area is the coordination chemistry of carbohydrate and its medicinal applications, such as anti-cancer drugs. When I worked with him, I recognised the potential of carbohydrates in medical applications. Currently, polyethylene glycol (PEG) is the first choice for water-soluble and biologically compatible polymers for drug delivery applications. In the future, I would like to make glycopolymer a functional alternative to PEG following a recently developed, controlled polymerisation technique.

Why did you choose Polymer Chemistry to publish your work?

My colleagues and I recognise that Polymer Chemistry is a high quality journal in this area.

In which upcoming conferences may our readers meet you?

I hope to attend the 2015 International Chemical Congress of Pacific Basin Societies (PACIFICHEM 2015).

How do you spend your spare time?

My wife and I love arts, especially 17th century Dutch painting, and animals (we love cats and dogs, and she deeply loves penguins!). However, it is not easy to see such masterpieces in Japan…

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

Even if I had not become a chemist, I would maybe have worked as a scientific engineer. I have never imagined joining any other kind of profession.

Aqueous RAFT synthesis of block and statistical copolymers of 2-(α-D-mannopyranosyloxy)ethyl methacrylate with 2-(N,N-dimethylamino)ethyl methacrylate and their application for nonviral gene delivery
Makoto Obata, Tomoya Kobori, Shiho Hirohara and Masao Tanihara
Polym. Chem., 2015,6, 1793-1804
DOI: 10.1039/C4PY01652A

Block copolymers composed of 2-(α-D-mannopyranosyloxy)ethyl methacrylate (ManEMA) and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) were synthesized by aqueous RAFT polymerization. The number-average degree of polymerization (DP_n) of ManEMA segments was constant at 33, and the DP_n of DMAEMA segments varied from 98 to 241. Statistical copolymers with a similar composition were also prepared via aqueous RAFT polymerization. The mannose-presenting nature was evaluated by a turbidimetric assay using Concanavalin A. The clustering rate of statistical copolymers was faster than those of the corresponding block copolymers. By contrast, no significant differences between block and statistical copolymers were found in their DNA-condensing ability as evaluated using gel shift assays and in their cytotoxicity in the transfection of plasmid DNA (pEGFP-N1) to HeLa cells. However, the overall transfection efficiency significantly depended on the monomer distribution. Statistical copolymers showed an overall transfection efficiency comparable to those of poly(DMAEMA·HCl)s, but block copolymers showed no detectable transfection under the same conditions.

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).

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Polymers curl up and take control

08 May 2015

By Kate Bandoo, Publishing Assistant.

Article written by Michaela Muehlberg

Scientists in Germany have successfully collapsed single polymer chains into dense nanoparticles, to make single-chain nanoparticles, by adding palladium.¹ The nanoparticles mimic enzymatic pockets with defined environments around their metal centres and can catalyse a carbon coupling reaction.

The intramolecular crosslinking process creates single-chain nanoparticles that catalyse a Sonogashira coupling reaction

Enzymes use their carefully shaped reaction cavities to selectively catalyse organic reactions. Industrial processes crave selectivity, but also demand straightforward procedures. Synthesising and separating enzymes in practical quantities is, however, tricky, so they aren’t always suitable for industry. One solution to this might be single-chain nanoparticles, which have recently become a hot topic in the field of polymer chemistry.² Their applications range from sensing to recognition, and medicine to catalysis, but only a few groups have studied their synthesis and even fewer have looked at the introduction of metals.

To read the full article visit Chemistry World.

Pd-complex driven formation of single-chain nanoparticles
Johannes Willenbacher, Ozcan Altintas, Vanessa Trouillet, Nicolai Knöfel, Michael J. Monteiro, Peter W. Roesky and Christopher Barner-Kowollik
Polym. Chem., 2015, Advance Article
DOI: 10.1039/C5PY00389J, Paper

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2015 Polymer Chemistry Lectureship awarded to Richard Hoogenboom

06 May 2015

By Katie Nicholson, Development Editor.

It is with great pleasure that we announce Professor Richard Hoogenboom (Ghent University) as the recipient of the inaugural 2015 Polymer Chemistry Lectureship award.

This award, which will be an annual event for the journal, honours an early-stage career researcher who has made significant contribution to the polymer chemistry field. The recipient is selected by the Polymer Chemistry Editorial Board from a list of candidates nominated by the community.

Read on to find out more about Richard…

Professor Richard Hoogenboom was born in 1978 in Rotterdam (the Netherlands) and studied chemical engineering at the Eindhoven University of Technology (the Netherlands). In 2005, he obtained his Ph.D. under the supervision of Professor Ulrich S. Schubert and continued working as a project leader for the Dutch Polymer Institute, partially combined with a position as senior product developer at Dolphys Medical BV. After postdoctoral training at the RWTH Aachen with Professor Martin Moeller and at the Radboud University Nijmegen with Professor Roeland Nolte, he was appointed as associate professor at Ghent University in 2010 and in October 2014 he was promoted to full professor. His research focuses on adaptive and responsive materials based on stimuli-responsive polymers, supramolecular polymers, and poly(2-oxazoline)s. Professor Hoogenboom has published more than 260 refereed scientific articles (h-index 47) and is currently Associate Editor for European Polymer Journal and Australian Journal of Chemistry.

To learn more about Richard’s research why not read his recent articles:

Dye immobilization in halochromic nanofibers through blend electrospinning of a dye-containing copolymer and polyamide-6
Iline Steyaert, Gertjan Vancoillie, Richard Hoogenboom and Karen De Clerck
Polym. Chem., 2015, 6, 2685-2694

Thermoresponsive polymeric temperature sensors with broad sensing regimes
Qilu Zhang, Gertjan Vancoillie, Maarten A. Mees and Richard Hoogenboom
Polym. Chem., 2015, 6, 2396-2400

Accelerated living cationic ring-opening polymerization of a methyl ester functionalized 2-oxazoline monomer
Petra J. M. Bouten, Dietmar Hertsen, Maarten Vergaelen, Bryn D. Monnery, Marcel A. Boerman, Hannelore Goossens, Saron Catak, Jan C. M. van Hest, Veronique Van Speybroeck and Richard Hoogenboom
Polym. Chem., 2015, 6, 514-518

We would like to thank everybody who nominated a candidate for the Lectureship; we received many excellent nominations, and the Editorial Board had a difficult task in choosing between some outstanding candidates.

Please join us in congratulating Richard by adding your comments below.

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Paper of the week: Patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures

24 Apr 2015

By Remzi Becer, web writer.

Palacios-Cuesta et al. describe the patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures.

Microorganisms have a remarkable ability to adhere to virtually any type of abiotic surface, proliferate and subsequently form biofilms. Since materials may need to interact differently with microorganisms, the adherent or repellent properties of materials towards bacteria are an extremely important consideration in their design. For example, materials used as implants need to remain free from contamination, in order to reduce device-associated infections, and hence, antifouling surfaces are prepared using water repellent polymers or by anchoring antimicrobial compounds. Conversely, surfaces capable of controlled immobilization and removal of microorganisms have been equally explored for a rather broad range of applications, including sophisticated systems such as biosensors or biomolecular motors. Thus far, precise immobilisation of microorganisms, and in particular bacteria, onto surfaces has been achieved by using a range of different fabrication approaches. However, there are relatively few examples of controlled immobilisation of single bacteria that don’t involve expensive approaches or time-consuming multistep procedures.

In this paper, Palacios-Cuesta and colleagues describe the development of different surface patterns using a photolithographic-based technique that does not require the use of high resolution masks or clean rooms and produces surface patterns with micrometer and submicrometer resolution. The procedure is based on the cross-linking and degradation processes occurring in polystyrene upon exposure to UV light. Together, these processes produce different patterns depending, not only on the mask, but also on the experimental conditions employed. With this approach it is possible to produce patterns with nanoscale resolution without expensive fine focalisation settings. Of particular interest, the authors demonstrate the feasibility of this strategy to incorporate functional groups to modulate the affinity between the bacteria and the surface. In particular, hydrophilic segments, i.e. poly(acrylic acid) that favour bacterial immobilisation are introduced. The strategy employed allows not only the incorporation of functional groups, but also enables the fine tuning of the amount of hydrophilic functional groups. This unique feature is used by the authors to determine the role of surface hydrophilicity on the adhesion of Staphylococcus aureus onto the different surface patterns. Finally, those surfaces on which both photodegradation and photo-cross-linking occur produce thin patterns largely below the micrometer that are then used to prepare arrays of isolated S. aureus bacteria. The formation of bacterial arrays of S. aureus on the single-cell level has been a challenge since they exhibit a large tendency to grow in clusters. This technology is exciting given its potential for enabling the isolation of single bacteria for diagnosis, and the study of bacterial populations at the single cell level.

Patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures by Marta Palacios-Cuesta, Aitziber L. Cortajarena, Olga García and Juan Rodríguez-Hernández, Polym. Chem., 2015, 6, 2677-2684.

Remzi Becer is a web-writer and Advisory Board member for Polymer Chemistry. He is currently a Senior Lecturer in Materials Science and the director of the Polymer Science and Nanotechnology masters programme at Queen Mary, University of London. Visit www.becergroup.com for more information.

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2015 International Polymer Colloids Group Conference

07 Apr 2015

By Pete Livermore, Deputy Editor.

We are pleased to announce the 2015 International Polymer Colloids Group Conference to be held on June 28 – July 3, 2015 at The University of New Hampshire, Durham, USA.

The 2015 program will bring together world leading scientists to discuss the latest developments in the area of colloidal polymer science. The talks of the invited speakers will feature a balance of traditional and emerging applications for polymer colloids, following the themes of colloids for life, engineering colloids, and colloidal machines. You can see a list of confirmed speakers here.

You can register for the 2015 IPCG Conference here.

SCIENTIFIC COMMITTEE

Prof. Stefan Bon, Conference Chair, Warwick University, UK
Prof. Jose R. Leiza, University of the Basque Country, Spain
Dr. Willie Lau, Oriental Yuhong, CN

ORGANIZING COMMITTEE

Prof. John Tsavalas, University of New Hampshire, USA

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Paper of the week: Nucleobase-functionalized acrylic ABA triblock copolymers and supramolecular blends

07 Apr 2015

By Remzi Becer, web writer.

Long et al describe the synthesis of nucleobase-functionalized acrylic triblock copolymers.

Reversible addition-fragmentation chain transfer (RAFT) polymerization afforded the unprecedented synthesis of well-defined acrylic ABA triblock copolymers with nucleobase-functionalized external blocks and a central poly(n-butyl acrylate) (PnBA) block. Size exclusion chromatography (SEC) confirmed the molecular weight and molecular weight distribution of the central block. ¹H NMR spectroscopy revealed the successful chain extension of the PnBA macro-chain transfer agent (CTA) using adenine or thymine-functionalized acrylic monomers. The acrylic monomer with a flexible spacer to the pendant nucleobases promoted intermolecular recognition of nucleobases and long range segmental motion of polymer main chains. The external block glass transition temperatures (T_g‘s) of thymine (T) and adenine (A) functionalized blocks were 52 °C and 76 °C, respectively. Thermomechanical and morphological analysis revealed the effect of processing conditions on self-assembly and microphase-separated morphology of nucleobase-functionalized ABA copolymers. Thymine and adenine-functionalized ABA triblocks formed a thermodynamically stable, hydrogen-bonded complex upon blending. The supramolecular blend exhibited a cylindrical microphase-separated morphology with an extended plateau window compared to the individual block copolymers. The complementary hydrogen bonding between adenine and thymine formed a thermally labile, physically crosslinked, network that exhibited enhanced mechanical performance with melt processability. Thus, these ABA nucleobase-functionalized block copolymers demonstrate potential as thermoplastic elastomers for hot melt adhesives and coatings.

Nucleobase-functionalized acrylic ABA triblock copolymers and supramolecular blends by Keren Zhang, Motohiro Aiba, Gregory B. Fahs, Amanda G. Hudson, William D. Chiang, Robert B. Moore, Mitsuru Ueda and Timothy E. Long Polym. Chem., 2015,6, 2434-2444

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Polymer Chemistry Blog

Author of the Month: Dr. Andreas Walther

Combining the incompatible: Block copolymers consecutively displaying activated esters and amines and their use as protein-repellent surface modifiers with multivalent biorecognition

Recent Appointees in Materials Science 2015 Conference (RAMS2015)

Paper of the Month: Rapid synthesis of ultrahigh molecular weight and low polydispersity polystyrene diblock copolymers by RAFT-mediated emulsion polymerization

Author of the Month: Prof. Makoto Obata

Top 10 most-read Polymer Chemistry articles – Q1 2015

Polymers curl up and take control

2015 Polymer Chemistry Lectureship awarded to Richard Hoogenboom

Paper of the week: Patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures

2015 International Polymer Colloids Group Conference

Paper of the week: Nucleobase-functionalized acrylic ABA triblock copolymers and supramolecular blends

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