Polymer Chemistry Blog

Polymer Chemistry Author of the Month: Christina Chai

15 Nov 2019

Christina Chai obtained her BSc (Hons) from the University of Canterbury, Christchurch, New Zealand and her PhD in organic chemistry from the Research School of Chemistry, Australian National University, Canberra under the mentorship of the late Professor Athel Beckwith, FRS. Following her PhD, she was awarded a Samuel and Violette Glasstone Research fellowship at the University of Oxford, UK. This was followed by a Faculty position in the Department of Chemistry, Victoria University of Wellington, NZ (1991-1993) and the Department and Research School of Chemistry, Australian National University (1994-2004) where she rose to the rank of a Reader. In 2005, Christina moved to Singapore to establish a research programme on synthetic and polymer chemistry at the then newly founded Institute of Chemical and Engineering Sciences, Agency for Science Technology and Research (A*STAR). She returned to a life in academia in 2011 at the Department of Pharmacy, National University of Singapore where she has held many administrative positions. She is currently Professor and the Head of the Department of Pharmacy. Although her major research interest is on bioactive compounds, she moonlights in polymer chemistry with special interest in biomimetic materials.

What was your inspiration in becoming a scientist who works with polymers?

My PhD training was in the area of free radical chemistry with one of the free radical ‘’gods’’, the late Professor Athel Beckwith. At that time, a superb team of chemists in CSIRO Australia had developed the RAFT process which was based on the principles of radical chemistry, and I was fascinated with the numerous possibilities of this process in creating new materials. Although this fascination remained after my PhD studies, I did not have the opportunity to work with polymers until I moved to A*STAR Singapore. I continue to be intrigued with clever ways of designing functional polymers for various applications.

What was the motivation behind your most recent Polymer Chemistry article?

When I first joined NUS, I received a grant that allowed me to work on biomimetic materials, specifically mussel-inspired coatings. I was intrigued with the claims that polydopamine (PDA) is a universal coating material, and was amazed with the reported applications of polydopamine. If one read and believed all the literature, one would imagine that PDA is the answer to all our material needs. As we worked to develop PDA functional coatings, we were hampered by the lack of information on the structure of PDA. We wanted to improve the properties of PDA but how do we improve a mystery material? So we set out to understand the oxidation chemistry of dopamine, and the process of coating and of course, to attempt to elucidate the structure of PDA. I was fortunate that my PhD student at that time, Lyu Qinghua was so obsessed with this mystery that he refused to submit his thesis until he knew the answer. I am not convinced that we have completely solved the mystery (although I did manage to persuade the student to submit his thesis) but I believe that we have made significant progress in the structural elucidation. The answer is just around the corner!

Which polymer scientist are you most inspired by?

In view of my training as a free radical chemist, I was most interested in the ability to control polymer synthesis through living free radical polymerisation methods such as ATRP and RAFT. I personally know Professor San Thang, now of Monash University, who is one of the co-inventors of RAFT, and his life story and his humility despite his successes is one of my inspiration. Professor K. Matyjaszewski, the guru of ATRP and Professor Craig Hawker, with his fascinating designs of functional polymers are also heroes in my eyes.

Can you name some up and coming researchers who you think will have a big impact on the field of polymer chemistry?

Professor Molly Stevens from Imperial College London is a name that comes to mind as her research on materials for biomedical applications will be a game changer.

How do you spend your spare time?

I love reading and travelling. I read fiction and non-fiction for pleasure. My love for travel is not about visiting places of interest but to immerse myself in a different environment and culture. Although I am an introvert, I am interested in people-watching. People are fascinating subjects for study!

What profession would you choose if you weren’t a scientist?

A doctor, a nun or a scientist – This is what I would say when I was a child when people asked me what I wanted to be when I grew up. As I doubt that I would be religious enough to qualify as a nun, this just leaves being a doctor as my alternate profession that I would choose. However I love being a scientist! I constantly worry about not having enough funds to support my research. My dream is to win the lottery so that I can support my research for the rest of my career…

Is the end in sight for the structural analysis of polydopamine? What important questions remain to be answered?

Yes, I believe that the end is in sight for the structural analysis of polydopamine. I believe that fundamental studies are important if we want to advance the applications. Without knowing the structure, how do we improve the properties of the material? There are still gaps in PDA technology that needs to be addressed. For example, one would need to know how to reproducibly control the thickness and homogeneity of the material; how to reduce the coloration and improve stability…. There is so much that we do not yet know.

Read Christina’s full article now for FREE until the 21st December!

Unravelling the polydopamine mystery: is the end in sight?

Qinghua Lyu, Nathanael Hsueh and Christina L. L. Chai

Despite the prominence of polydopamine (PDA) in the field of polymer and materials chemistry since it was first reported by H. Lee, S. M. Dellatore, W. M. Miller and P. B. Messersmith, Science, 2007, 318, 426–430, the structure of PDA has been an unresolved and contentious issue. Current consensus favors polymers derived from the cyclized intermediate 5,6-dihydroxyindole (DHI). In this work, compelling evidence for the possible structure of PDA is shown via detailed mass spectroscopic studies using deuterium-labeled dopamine (DA) precursors. More specifically, the major component of PDA is shown to derive from dopaminochrome (DAC) and uncyclized DA components. One major intermediate, seen at m/z 402, is characterized as a combination of benzazepine + DAC + 2H-pyrrole, which has a chemical formula of C₂₃H₂₀N₃O₄. Furthermore, DAC forms stable complexes with DA, and is a key control point in the polymerization of PDA. The decay of DAC into DHI is a relatively slow process in the presence of excess DA, and plays a smaller role in PDA formation. This study shows the covalent connectivity in PDA from the starting DA monomer, and represents an important advance in elucidating the structure of PDA.

About the Webwriter

Simon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based in the Laboratoire des IMRCP in Toulouse. His research seeks to apply a fundamental understanding of polymerization kinetics and mechanisms to the development of new materials. He is an Advisory Board member for Polymer Chemistry. Follow him on Twitter @polyharrisson

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Paper of the month: Ab initio RAFT emulsion polymerization mediated by small cationic RAFT agents to form polymers with low molar mass dispersity

01 Nov 2019

By Athina Anastasaki, Web Writer.

Stace et al. employ small cationic RAFT agents to produce low dispersity polymers in ab initio emulsion polymerization.

Reversible addition fragmentation chain transfer (RAFT) polymerization has revolutionized the field of polymer chemistry providing access to a wide range of materials with controlled molecular weight, functionality, end-group fidelity and dispersity. In their current contribution, the groups of Moad, Keddie and Fellows joined forces to report a range of low molar mass cationic RAFT agents that allow for predictable molecular weight and dispersity in ab initio emulsion polymerization. In particular, upon utilizing the protonated RAFT agent ((((cyanomethyl)thio)carbonothioyl)(methyl)amino)pyridin1-ium toluenesulfonate and the analogous methyl-quaternized RAFT agents, 4-((((cyanomethyl)thio) carbonothioyl)(methyl)amino)-1-methylpyridin-1-ium dodecyl sulfate, styrene could be efficiently polymerized yielding polystyrene with narrow molecular weight distributions (Đ_m 1.2–1.4). The authors attribute the success of ab initio emulsion polymerization with the former RAFT agent to the hydrophilicity of the pyridinium group which allows for the predominant partition of the water-soluble RAFT agent into the aqueous phase. The RAFT agent also gives minimal retardation. In addition, by employing 4-((((cyanomethyl)thio) carbonothioyl)(methyl)amino)-1-methylpyridin-1-ium dodecyl sulfate, a “surfactant-free” RAFT emulsion can be achieved producing a low Đ_m polystyrene although the RAFT end-group was lost upon isolating the polymer. Additional preliminary experiments were also performed demonstrating that this class of RAFT agents can be broadly applicable in ab initio emulsion polymerization of a range of other more-activated monomers including acrylates and methacrylates producing low dispersity polymers while the polymerization of less activated monomers such as vinyl acetate showed good control over the molecular weight, albeit broader molecular weight distributions. The authors are currently investigating such systems to establish their full utility in emulsion polymerization and develop robust and scalable conditions for the formation of block copolymers.

Tips/comments directly from the authors:

There are two significant challenges in implementing successful ab initio emulsion polymerization in a high throughput platform such as the Chemspeed®

Devising a protocol for vortexing/agitating so as to form, and then maintain, a stable latex. The protocol reported was the end-result of many experiments.
Degassing the reaction medium. RAFT polymerization can be successfully carried out in non-degassed media. However, for good reproducibility, optimal dispersity, high end group fidelity and acceptable polymerization rates, degassing remains important. In conducting experiments on the Chemspeed®, it is important to make sure the media to be dispensed by the robot are degassed, and that all of the solvent lines, and the solvent used to prime and wash the syringe needles are degassed.

Read the full article for FREE until 6th December!

Ab initio RAFT emulsion polymerization mediated by small cationic RAFT agents to form polymers with low molar mass dispersity, Polym. Chem., 2019, 10, 5044-5051, DOI: 10.1039/C9PY00893D

About the Web Writer

Dr. Athina Anastasaki is an Editorial Board Member and a Web Writer for Polymer Chemistry. Since January 2019, she joined the Materials Department of ETH Zurich as an Assistant Professor to establish her independent research group.

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Paper of the month: Benchtop flow-NMR for rapid online monitoring of RAFT and free radical polymerisation in batch and continuous reactors

30 Sep 2019

By Athina Anastasaki, Web Writer.

Knox et al. utilize a benchtop flow-NMR for rapid online monitoring of a range of polymerisation methodologies.

To precisely engineer macromolecular materials, close monitoring of the polymerization progress is required. Therefore, real-time online monitoring provides polymer chemists the opportunity to accurately observe and optimize their reactions. To this end, Warren and co-workers utilized benchtop flow-nuclear magnetic resonance (NMR) as a very convenient and powerful tool for real-time monitoring of polymers synthesized either by controlled radical polymerization or free radical polymerization protocols. In particular, reversible addition-fragmentation chain-transfer (RAFT) polymerization was employed to polymerize acrylamides giving very high conversions in less than 10 minutes and the kinetic profile of this reaction was efficiently captured. In a second example where RAFT dispersion polymerization was monitored. In spite of the rapid polymerization rates, high temporal resolution enabled the previse determination of the onset of rate acceleration usually observed for polymerization induced self-assembly (PISA) systems. In addition to the monitoring of the aforementioned complex systems, the free radical polymerization of methyl methacrylate was also studied. In this case, the linear semi-logarithmic plot indicated the expected pseudo-first order kinetics. The results discussed here demonstrate the power of using benchtop NMR spectrometers for online flow applications where both controlled and free radical polymerizations can be employed. It is the author’s opinion that the lower price of these instruments will improve access to NMR spectroscopy while the reduced sample preparation/time taken for analysis will increase research output.

Tips/comments directly from the authors:

Despite the reduced field strength, detailed polymerization kinetics comparable to traditional ‘high field’ NMR can be obtained since the vinyl protons are easily resolved.
Flow-NMR is a powerful tool to improve time-resolution and reduce lab workload but must be used with care – e.g. flow rate and sample cell geometry must be optimized.
Hydrogenated solvents can be used with lower-field instruments, but solvent selection is important: minimising any potential solvent overlap is key to reliable data.
Spectral corrections such as to the phase and baseline are crucial for reliable data – especially if using an automated system.

Read the full article now for FREE until 8th November!

Benchtop flow-NMR for rapid online monitoring of RAFT and free radical polymerisation in batch and continuous reactors, Polym. Chem., 2019, 10, 4774-4778, DOI: 10.1039/C9PY00982E

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Polymer Chemistry Author of the Month: April Kloxin

25 Sep 2019

By Simon Harrisson.

April M. Kloxin, Ph.D., is an Associate Professor in Chemical & Biomolecular Engineering and Materials Science & Engineering at the University of Delaware (UD) and a member of the Breast Cancer Research Program at the Helen F. Graham Cancer Center and Research Institute in the Christiana Care Health System. She obtained her B.S. and M.S. in Chemical Engineering from North Carolina State University and Ph.D. in Chemical Engineering from the University of Colorado, Boulder, as a NASA Graduate Student Research Program Fellow. She trained as a Howard Hughes Medical Institute postdoctoral research associate at the University of Colorado before joining the faculty at UD in 2011. Her group aims to create unique materials with multiscale property control for addressing outstanding problems in human health. Her research currently focuses on the design of responsive and hierarchically structured soft materials and development of controlled, dynamic models of disease and regeneration. Her honors include the Biomaterials Science Lectureship 2019, ACS PMSE Arthur K. Doolittle Award 2018, a Susan G. Komen Foundation Career Catalyst Research award, a NSF CAREER award, and a Pew Scholars in Biomedical Sciences award.

What was your inspiration in working with polymers?

I have always enjoyed building things and had a desire to use those skills to help people. I discovered my passion for using chemical approaches to build soft polymeric materials possessing unique and useful properties as an undergraduate and Master’s student at North Carolina State University (NCSU). At NCSU, I had the opportunity to work in a collaborative environment with many extraordinary friends and colleagues having great polymer science and engineering expertise, including my MS thesis advisors Profs. Rich Spontak and Stuart Cooper. This experience helped me understand the connection between molecular design and synthetic approaches for building polymeric materials with specific properties for a desired application. I had the opportunity to fully realize and direct this passion working at the interface between polymeric materials and biological systems under the outstanding advisement and mentorship of Prof. Kristi Anseth at the University of Colorado, Boulder, for my Ph.D. and with the many remarkable researchers in her group and at the University.

What was the motivation behind your most recent Polymer Chemistry article?

From a biological perspective, my group has a focus on understanding how changes in the structure, mechanical properties, and compositions of tissues in the human body that occur upon injury influence the function and fate of key cells in healing and disease. In this context, we have been interested in building synthetic mimics of these complex systems and processes, and we wanted to establish simple yet effective approaches for controlling the density and stiffness of soft materials when and where desired for hypothesis testing. In the Polymer Chemistry manuscript, we were inspired by the work of Prof. Matt Becker (Duke University) amongst others demonstrating how the rate of formation of water-swollen polymer networks, hydrogels, could be used to control defect formation, network heterogeneity, and thereby the mechanical properties of the resulting materials. We hypothesized that the rate-based control of properties that others observed with catalyzed step growth reactions was translatable to a photo-polymerized system, affording the implementation of a variety of photochemical controls (e.g., wavelength, intensity, time). In particular, by selecting a wavelength of light that was not centered at the maximum absorption of the photoinitiator, we were better able to control the rate of photopolymerization with an accessible bench-top visible light LED system and thereby defect formation. We then saw an opportunity to exploit dangling-end defects that were generated with this rate-based approach to increase crosslink density and ‘stiffen’ these materials with a secondary photopolymerization. We are excited about the potential that this light-triggered rate-based approach for controlling mechanical properties of polymer networks has for a number of applications, including our on-going studies of cell response to matrix stiffening.

Which polymer or materials scientists are you most inspired by?

Oh, there are so many! I am especially inspired by the work and leadership of Prof. Paula Hammond (MIT) and Prof. Kristi Anseth, who continue to blaze trials at the interface between polymers, materials, and biology to solve complex problems, and Prof. Chris Bowman (University of Colorado, Boulder) and the late Prof. Charlie Hoyle (University of Southern Mississippi), who have pioneered the use of light-triggered step growth reactions for creating polymeric materials with diverse and robust properties.

Can you name some up and coming polymer chemists who you think will have a big impact on the field?

It is an exciting time in polymer chemistry with many excellent researchers working from different perspectives to advance not only the field of polymer chemistry, but also to make fundamental breakthroughs that have an impact in biology, medicine, and energy. Selecting just a few is difficult in this context. A few that come to mind at the moment whose work I find particularly inspiring are Prof. Aaron Esser Kahn (University of Chicago) in biomolecular design of polymeric materials for rewiring the immune system, Prof. Dominik Konkolewicz (Miami University Ohio) in bioconjugations and dynamic covalent chemistries with polymeric materials, Prof. Rachel A. Letteri (University of Virginia) in peptide-polymer conjugates for multi-scale and dynamic properties, and my own new colleague Prof. Laure Kayser (University of Delaware) in conducting and semiconducting polymers.

How do you spend your spare time?

I enjoy making things, from designing materials at work to preparing satisfying meals in the kitchen at home. Breakfast foods are my favorite, and I have different recipes that I continue to hone on weekends for quick meals during the week. I also love being outside walking, hiking, or running with my friends or my husband and our two sons, particularly in the beautiful early autumn weather we currently are having.

What profession would you choose if you weren’t a chemist?

My obsession with the complexity of biological systems and improving human health would keep me in science and engineering, whether in molecular biology or bioinformatics or more applied in medicine.

Read April’s recent Polymer Chemistry article now for FREE until 31st October!

Rate-based approach for controlling the mechanical properties of ‘thiol–ene’ hydrogels formed with visible light

The mechanical properties of synthetic hydrogels traditionally have been controlled with the concentration, molecular weight, or stoichiometry of the macromolecular building blocks used for hydrogel formation. Recently, the rate of formation has been recognized as an important and effective handle for controlling the mechanical properties of these water-swollen polymer networks, owing to differences in network heterogeneity (e.g., defects) that arise based on the rate of gelation. Building upon this, in this work, we investigate a rate-based approach for controlling mechanical properties of hydrogels both initially and temporally with light. Specifically, synthetic hydrogels are formed with visible light-initiated thiol–ene ‘click’ chemistry (PEG-8-norbornene, dithiol linker, LAP photoinitiator with LED lamp centered at 455 nm), using irradiation conditions to control the rate of formation and the mechanical properties of the resulting hydrogels. Further, defects within these hydrogels were subsequently exploited for temporal modulation of mechanical properties with a secondary cure using low doses of long wavelength UV light (365 nm). The elasticity of the hydrogel, as measured with Young’s and shear moduli, was observed to increase with increasing light intensity and concentration of photoinitiator used for hydrogel formation. In situ measurements of end group conversion during hydrogel formation with magic angle spinning (MAS ¹H NMR) correlated with these mechanical properties measurements, suggesting that both dangling end groups and looping contribute to the observed mechanical properties. Dangling end groups provide reactive handles for temporal stiffening of hydrogels with a secondary UV-initiated thiol–ene polymerization, where an increase in Young’s modulus by a factor of ∼2.5× was observed. These studies demonstrate how the rate of photopolymerization can be tuned with irradiation wavelength, intensity, and time to control the properties of synthetic hydrogels, which may prove useful in a variety of applications from coatings to biomaterials for controlled cell culture and regenerative medicine.

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Paper of the month: Engineering mannosylated nanogels with membrane-disrupting properties

10 Sep 2019

By Athina Anastasaki, Web Writer.

De Coen et al. develop the engineering mannosylated nanomaterials with membrane-disruptive properties.

Engineering mannosylated nanomaterials with various functionalities can significantly contribute to the development of more effective vaccines or cancer immunotherapeutics that target immune cell subsets that express the mannose receptor. With this in mind, De Geest’s group aimed at equipping mannosylated nanogels with membrane-destabilizing properties that are responsive to the acidic pH found in intracellular vesicles, such as endosomes, but are shielded when the nanogels are intact in neutral pH. In particular, membrane destabilizing tertiary amine moieties were successfully introduced in the core of the nanogels. Subsequently and via using a pH-sensitive ketal-based crosslinker, the membrane-destabilizing properties only become activated upon pH-triggered disassembly of the nanogels into soluble unimers. In order to achieve this, the effect of tertiary amine modification of mannosylated block copolymers with N,N-dimethylamine (DMAEA) and N,N-diisopropylamine (DiPAEA) was initially evaluated. Both block copolymers showed strong haemolytic activity and the DiPAE block copolymers demonstrated an activity only at acidic endosomal pH values. To silence the membrane destabilizing activity and render the nanogels non-cytotoxic at high concentration, cross-linking of the block copolymers into nanogels was conducted. Interestingly, when a pH degradable ketal cross-linker was used, the nanogels could regain their activity by exposing them to mild acidic pH. As the authors nicely conclude, such synthetic mannosylated materials may hold promise for cytoplasmic delivery of non-membrane permeable therapeutic macromolecules.

Tips/comments directly from the authors:

Dendritic cells and macrophages reside in peripheral tissue, lymphoid organs and sites of inflammation and tumor tissue. They are a primary therapeutic target.
The use of tetraacetylated carbohydrate monomers allows for straightforward polymerization and work-up in organic media. Deacetylation is easily performed in a final step and yields hydrophilic glyconanogels.
The use of a pentafluorophenyl activated ester hydrophobic polymer bock allows for self-assembly in aprotic polar solvents. This is ideal for successive post-modification steps without facing hydrolysis as a side reaction.
Diisopropylamine motifs are highly efficient in destabilizing lipid membranes at acidic pH, presumably through hydrophobic interaction with phospholipid membranes.

Read this article for FREE until the 15th October!

Engineering mannosylated nanogels with membrane-disrupting properties Polym. Chem., 2019, 10, 4297-4307, DOI: 10.1039/C9PY00492K

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Nominations now open for the 2020 Polymer Chemistry Lectureship

02 Sep 2019

By Garima Sharma, 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 the 2020 Polymer Chemistry Lectureship. 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.

The recipient of the award will be asked to present a lecture at the Warwick Polymer Meeting in 2020, where they will also be presented with the award. The Polymer Chemistry Editorial Office will provide financial support to the recipient for travel and accommodation costs.

The recipient will also be asked to contribute a lead article to the journal and will have their work showcased free of charge on the front cover of the issue in which their article is published.

Dr Frederik Wurm receiving his Lectureship award from Dr Neil Hammond (left) and Professor Filip Du Prez (right) at the EPF 2019

Previous winners

2019 – Frederik Wurm, Max Planck Institute for Polymer Research, Germany

2018 – Cyrille Boyer, University of New South Wales, Australia

2017 – Julien Nicolas, Université Paris Sud, France

2016 – Feihe Huang, Zhejiang University, China

2015 – Richard Hoogenboom, Ghent University, Belgium

Eligibility

To be eligible for the lectureship, candidates should meet the following criteria:

Be an independent researcher, having completed PhD and postdoctoral studies
Be actively pursuing research within the polymer chemistry field, and have made a significant contribution to the field
Be at an early stage of their independent career (this should be within 15 years of attaining their doctorate or equivalent degree, but appropriate consideration will be given to those who have taken a career break, for example for childcare leave, or followed an alternative study path)

Although the Polymer Chemistry Lectureship doesn’t explicitly reward support of or contributions to the journal, candidates with no history of either publishing in or refereeing for the journal would typically not be considered.

Selection

Eligible nominated candidates will be notified of their nomination, and will be asked to provide 3 recent articles that they feel represent their current research.
All eligible nominated candidates will be assessed by a shortlisting panel, made up of members of the Polymer Chemistry Advisory Board and a previous lectureship winner.
The shortlisting panel will consider the articles provided by the candidates as well as their CVs and letters of nomination.
Shortlisted candidates will be further assessed by the Polymer Chemistry Editorial Board, and a winner will be selected based on an anonymous poll.
Selection is not based simply on quantitative measures. Consideration will be given to all information provided in the letter of recommendation and candidate CV, including research achievements and originality, contributions to the polymer chemistry community, innovation, collaborations and teamwork, publication history, and engagement with Polymer Chemistry.

Nominations

Nominations must be made via email to polymers-rsc@rsc.org, and should include a short CV (3 page maximum length) and a brief letter of nomination (1 page maximum length)
Self-nomination is not permitted
Nominators do not need to be senior researchers, and we encourage nominations from people at all career levels
As part of the Royal Society of Chemistry, we believe we have a responsibility to promote inclusivity and accessibility in order to improve diversity. Where possible, we encourage each nominator to consider nominating candidates of all genders, races, and backgrounds.
Candidates outside of the stated eligibility criteria may still be considered

Nominations should be submitted no later than 30^th November 2019

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Polymer Chemistry Author of the Month: Daniel Crespy

30 Jul 2019

By Simon Harrisson.

Daniel Crespy studied chemistry at the University of Strasbourg where he first came in contact with the field of heterophase polymerizations. He joined Professor Katharina Landfester in 2003 to complete a PhD in the University of Ulm where he developed novel methods to prepare nanocapsules in miniemulsion. In 2006, he held a position as project leader at Empa (Swiss Federal laboratories for Materials Research and Technology), working on stimuli-responsive materials for textile applications. He joined the department of Professor K. Landfester at the Max Planck Institute for Polymer Research (Mainz, Germany) in July 2009 as group leader. Since 2016, Daniel Crespy is an Associate Professor at the Vidyasirimedhi Institute of Science and Technology (VISTEC) in Rayong, Thailand.

What was your inspiration in becoming a polymer chemist?
Since childhood, I was fascinated by fireworks, paintings, and nature. I was interested in chemistry when I understood that movements and colors, as well as the emotions lived by the observer were produced by chemical reactions. I love chemistry because chemists can shape reality to create new materials adapted to our needs. In my view, polymer chemistry is particularly interesting because it encompasses all traditional fields of chemistry. I am definitively in debt to all the professors in chemistry and polymer science who were patient enough and enthusiastic to teach us the basics.

What was the motivation behind your most recent Polymer Chemistry article?
The aim was to create polymer nanoparticles that are decorated with cyclic carbonate groups. We demonstrated that these nanoparticles can be further functionalized with a large variety of molecules, including amino acids and proteins. The work was completed with my colleague Assist. Prof. Valerio D’Elia, who is specialist in converting CO₂ to industrially important chemicals. The carbonate-functionalized particles were used as heterogeneous catalysts for carbonation reactions using CO₂. Basically, we showed that a catalyst partially made from CO₂ and other sustainable chemicals can be used to produce other useful chemicals from CO₂. We believe that this paper will find an echo in the greater context of sustainable chemistry.

Which polymer scientist are you most inspired by?
I admire the professional achievements of Wallace Carothers who made significant contributions to both applied and fundamental research in polymer chemistry. Before my PhD studies, I was already following closely the work on heterophase polymerization of Mohamed El-Aasser, Katharina Landfester, Markus Antonietti, Klaus Tauer, Jose-Maria Asua, Bob Gilbert, Masayoshi Okubo, and Massimo Morbidelli. In parallel, I liked to read the contributions of Rolf Mulhaupt and Hans Rytger Kricheldorf on other topics of polymer chemistry. Working with Katharina Landfester had definitively a very large and positive impact on me, my working style, and my research so that I cannot be thankful enough towards her.

Can you name some up and coming polymer chemists who you think will have a big impact on the field?
I have too much respect for the work of other scientists to select people who will have a big impact on the field. We live in a time where spectacular papers are momentarily impactful but only time will truly select which contributions will stay in the classical textbooks of tomorrow. I can say that I am very impressed by the quality and quantity of talented polymer chemists from China, especially the scientists who tackle fundamental research. Finally, I do hope that my ex-students will have a big impact on the field in their future career.

How do you spend your spare time?
I am addicted to the positive sensation of collective achievement experienced when playing football. I also read a lot about Thai culture, which is for me both mysterious and fascinating. Finally, I am organizing an association to explain Thai students how to get scholarships from Germany to study in Germany.

What profession would you choose if you weren’t a chemist?

I would be geneticist, who is a kind of polymer chemist but specialized in polynucleotides.

Read Daniel’s recent Polymer Chemistry article now for FREE until 31st August!

Versatile functionalization of polymer nanoparticles with carbonate groups via hydroxyurethane linkages

Neha Yadav, Farzad Seidi, Silvano Del Gobbo, Valerio D’Elia* and Daniel Crespy*

Synthesis of polymer nanoparticles bearing pendant cyclic carbonate moieties is carried out to explore their potential as versatile supports for biomedical applications and catalysis. Nanoparticles are produced by copolymerizing glycerol carbonate methacrylate with methyl methacrylate by the miniemulsion process. The ability of the nanoparticles to serve as carriers for biomolecules was studied by reacting them with various amines, amino acids, and proteins. The functionalized nanoparticles are systematically analyzed by Fourier transform infrared spectroscopy, solid state (SS) NMR spectroscopy, and X-ray photoelectron spectroscopy. Model studies are performed to investigate the reactivity of amino acids and albumin with the pendant carbonate groups. Functionalization of the nanoparticles with dopamine led to surface coverage with catechol groups as efficient heterogeneous hydrogen bond donors for the cycloaddition of CO₂ to epoxides under atmospheric pressure

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Paper of the month: Bottom-up design of model network elastomers and hydrogels from precise star polymers

26 Jul 2019

By Athina Anastasaki, Web Writer.

Creusen et al. developed a new type of building blocks that allow access to model network elastomers using precise polymer chemistry.

Synthetic polymer networks have attracted considerable attention owing to their exceptional mechanical properties including high resilience and toughness. Such materials are typically based on multi-arm poly(ethylene glycol) (PEG) which is a commercially available compound. However, PEG networks suffer from restricted access to higher molecular weight which limits the network dimensions. In addition, the crystalline nature of PEG does not allow for a comprehensive understanding of the mechanical behaviour in bulk network elastomers. To overcome this challenge, Walther and co-workers introduced a new class of high molecular weight star polymer building blocks for the construction of model network elastomers and hydrogels with tuneable mechanical properties. To achieve this, triethylene glycol methyl ether acrylate was successfully polymerized via light-inducted atom transfer radical polymerization and Cu(0)-wire reversible deactivation radical polymerization, yielding well-defined polymers with narrow molecular weight distributions and high end-group fidelity. Upon synthesis, functional motifs were introduced within the polymer through either post-polymerization modification of the bromine end-groups or the use of a fluorescent star initiator. In particular, the introduction of norbornene end-groups allowed for the subsequent crosslinking of the materials in presence of a photo-radical initiator. This allowed access to thermally reversible model network hydrogels based on dynamic supramolecular bonds. Overall, this work enables the simultaneous study of the mechanical behaviour of bulk network elastomers and swollen hydrogens with the same network topology. As the authors elude in their conclusions, by elegantly exploiting precision polymer chemistry, our understanding of architecture control can be enhanced leading to the rational design of functional mechanical network materials.

Tips/comments directly from the authors:

Water-soluble star polymers with a low T_g and quantitative end-group introduction allow the simultaneous investigation of identical model networks as hydrogels and bulk elastomers.
The monomer triethylene glycol methyl ether acrylate (mTEGA) yields low-T_g, water-soluble polymers. A distinct advantage over other oligo(ethylene glycol) acrylates is the absence of potential diacrylate impurities compromising polymerization control.
Polymerization of mTEGA by photo-induced and Cu⁰-catalyzed Cu-RDRP from commercial and functional 4-arm initiators yields narrowly dispersed star polymers up to high molecular weights. In order to achieve optimal control with minimal side reactions, a balance in the initiator-to-CuBr₂ ratio is necessary.
Cu⁰-mediated Cu-RDRP is suitable for scale up, and the polymers can be isolated by precipitation into 85/15 diethyl ether/n-pentane followed by salt removal through neutral alumina.
Following end-group transformation with primary amines, both excess amines and bromide salts must be removed. The former is removed through precipitation, the latter by taking the polymer up into a diethyl ether/THF mixture and removing insoluble components.
Constructing hydrogels by photo-crosslinking 4-arm p(mTEGA)-norbornene with a bifunctional thiol is fast (<1 min) with the photo-radical initiator LAP and slower (>30 min) with Irgacure-2959.
Supramolecular hydrogels constructed from 4-arm p(mTEGA)-terpyridine with divalent metal ions are highly dependent on the metal. Zn^II yields hydrogels which are dynamic at room temperature, and increasingly so upon heating making them suitable for thermal 3D-printing.

Read the full Paper now for FREE until the 31st August!

Bottom-up design of model network elastomers and hydrogels from precise star polymers, Polym. Chem., 2019, 10, 3740-3750, DOI: 10.1039/c9py00731h

About the web writer
Dr. Athina Anastasaki is an Editorial Board Member and a Web Writer for Polymer Chemistry. Since January 2019, she joined the Materials Department of ETH Zurich as an Assistant Professor to establish her independent research group.

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Polymer Chemistry Author of the Month: Yasuhiro Kohsaka

12 Jul 2019

By Simon Harrisson.

Yasuhiro Kohsaka is an Associate Professor in the Research Initiative for Supra-Materials (RISM) and the Faculty of Textile Science and Technology (FTST) at Shinshu University. He started his academic career as a JSPS Research Fellow in 2008 researching supramolecular polymer chemistry under the supervision of Prof. Toshikazu Takata at Tokyo Tech. From 2009 to 2010 he studied as a visiting student under Prof. Timothy Swager at MIT. He received his Ph. D. degree in Engineering at 2011 from Tokyo Tech. He worked as an Assistant Professor in Prof. Tatsuki Kitayama’s group in Graduate School of Engineering Science at Osaka University. In 2015, he moved to FTST at Shinshu University as a Tenure-Track Assistant Professor supported by JST and established his own independent research group. He became an Associate Professor in 2018, and joined the RISM in 2019. Since 2019, he has started a new project on the design of new monomers and polymerization chemistry using synergetic effects of two or more functional groups. His research is always based on pure organic chemistry but proposed with practical application in mind. Therefore, he has interests in both polymer chemistry and material science. He was chosen as one of the Emerging Investigators of 2018 in Polymer Chemistry. Recently, he received a Young Researcher Award from the Society of Polymer Science, Japan (SPSJ) and the Society of Fiber Science and Technology, Japan (SFSTJ).

What was your inspiration in becoming a polymer chemist?

In childhood, my uncle often entertained me with plastic models of airplanes. This experience made me interested in science and technology. However, my favorite subjects were not chemistry but astronomy and earth science. Therefore, I attempted to join the astronomy club in the first year of middle high school, but the atmosphere was not comfortable for me. Then, my friend induced me to join chemistry club, where senior high school students were studying the synthesis of biodegradable plastics. This was my first introduction to polymer chemistry. In 2000, Prof. Hideki Shirakawa won the Nobel Prize in Chemistry for his discovery of conductive polymers. This news had a strong impact on me. I also learned that our daily life was supported by polymer materials, such as plastics, rubbers, fibers and adhesives. Then, I dreamed to develop new functional polymer materials like Prof. Shirakawa and change our life for the better. After that, I am striking out to my dream even now!

What was the motivation behind your most recent Polymer Chemistry article?

This is completely a kind of serendipity. Hemiacetal esters are interesting molecules, as they can be used for various purposes. The formation of a hemiacetal ester bond is reversible and thus it can be applied to dynamic covalent chemistry, while hemiacetal esters can also initiate living cationic polymerization of vinyl ethers. On the other hand, cyclic hemiacetal esters give two different types of polymers, polyesters and poly(hemiacetal ester)s, by ring-opening polymerization (ROP). Therefore, we have interests in the polymerization chemistry of cyclic hemiacetal esters containing polymerizable vinyl groups, as the monomers can undergo both ROP and vinyl polymerization and each product would have the respective potential application according to its residual groups. In our previous paper, therefore, we reported the vinyl polymerization of cyclic hemiacetal esters with acrylate skeleton (J. Polym. Sci. Part A: Polym. Chem. 2016, 54, 955). This monomer contains a hemiacetal ester skeleton, but we are also interested in cyclic ketene acetal esters, which provide hemiacetal ester skeletons by vinyl polymerization. That is, the vinyl polymerization changes the double bond to single bond forming a hemiacetal ester skeleton in the process. For this concept, we sought a cyclic ketene acetal ester in the database and found dehydroaspirin. Therefore, we never aimed to recycle vinyl polymers.

Which polymer scientist are you most inspired by?

Since I am interested in the principles of step-growth polymerization, Prof. Mitsuru Ueda’s (NTU) early papers such as group-selective polycondensation and synthesis of regio-regular polymers always give me a good inspiration. As I conduct a project on ring-opening polymerization, I am also inspired by Prof. Marc Hillmyer (University of Minnesota).

Can you name some up and coming polymer chemists who you think will have a big impact on the field?

I respect Prof. Koji Takagi’s (Nagoya Institute of Technology) energetic activity. He proposes unique and sophisticated approaches in polymer synthesis and collaborates with many young professors to advance his research. His molecular design is simple, but his deep insight and wide viewpoint present the importance of intelligence and dreams of polymer chemistry to our young generations. Speaking about our generations, my best friends, Prof. Hiroaki Imoto (Kyoto Institute of Technology), and Prof. Fumitaka Ishiwari (Tokyo Tech), my junior in school, are the closest but farthest researchers. Their motivation is very pure, and thus, the impacts of the completed results are always strong.

How do you spend your spare time?

As I work away from my family due to business reason, I enjoy driving home to spend the weekend with my wife and children. I like to play with my daughter (four years old) and son (two years old) with my children’s mind. On weekdays, I play and watch Shogi, a Japanese traditional board game like a chess. The way of thinking in Shogi is similar to that in organic chemistry, as the construction and motion of cooperated pieces (atoms) are the keys to winning. I also like to watch sports, particularly baseball and Formula One (F1).

What profession would you choose if you weren’t a chemist?

Earth scientist or astronomer, as they are my first dream in childhood. As it turns out, I am a natural scientist!

Read Yasuhiro’s recent Polymer Chemistry article for FREE until 19th August!

Radical polymerization of ‘dehydroaspirin’ with the formation of a hemiacetal ester skeleton: a hint for recyclable vinyl polymers

Akane Kazama and Yasuhiro Kohsaka

A vinyl polymer with a cyclic hemiacetal ester skeleton was synthesized via the radical polymerization of 2-methylene-4H-benzo[d][1,3]dioxin-4-one (MBDO; so-called ‘dehydroaspirin’). This material could be decomposed to acetic acid and salicylic acid (the raw ingredients for MBDO) by acid hydrolysis, and thus has potential as a recyclable vinyl polymer.

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Polydays 2019 – Polymer Science and Engineering in View of Digitalization

03 Jul 2019

By Garima Sharma, Deputy Editor.

The Polydays 2019 conference, taking place in Berlin on the 11th – 13th September, will focus on the transformation of material research by digital technologies, initiated by the Berlin-Brandenburg Association of Polymer Research (BVP) and organized by the Helmholtz-Zentrum Geesthacht (HZG). The conference will be chaired by Prof. Andreas Lendlein (Institute of Biomaterial Science, HZG) and co-chaired by Prof. Hans Börner (Institute of Chemistry, Humboldt-Universität zu Berlin).

Confirmed plenary speakers:
– Amanda Barnard, CSIRO, Melbourne, Australia
– Andrew I. Cooper, University of Liverpool, UK
– Jean-François Lutz, CNRS-Institute Charles Sadron, Strasbourg, France
– E. W. (Bert) Meijer, Eindhoven University of Technology, Netherlands
– Roeland Nolte, Radboud University, The Netherlands
– H. Jerry Qi, Georgia Institute of Technology, Atlanta, USA

Key dates
12th July – abstract submission deadline
31st July – early bird registration deadline

For more information please refer to the conference webpage: www.hzg.de/polydays2019

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Polymer Chemistry Blog

Polymer Chemistry Author of the Month: Christina Chai

Read Christina’s full article now for FREE until the 21st December!

Paper of the month: Ab initio RAFT emulsion polymerization mediated by small cationic RAFT agents to form polymers with low molar mass dispersity

Paper of the month: Benchtop flow-NMR for rapid online monitoring of RAFT and free radical polymerisation in batch and continuous reactors

Polymer Chemistry Author of the Month: April Kloxin

Read April’s recent Polymer Chemistry article now for FREE until 31st October!

Rate-based approach for controlling the mechanical properties of ‘thiol–ene’ hydrogels formed with visible light

Paper of the month: Engineering mannosylated nanogels with membrane-disrupting properties

Nominations now open for the 2020 Polymer Chemistry Lectureship

Polymer Chemistry Author of the Month: Daniel Crespy

Paper of the month: Bottom-up design of model network elastomers and hydrogels from precise star polymers

Polymer Chemistry Author of the Month: Yasuhiro Kohsaka

Polydays 2019 – Polymer Science and Engineering in View of Digitalization

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