Author Archive

Polymer Chemistry Author of the Month: Georges M. Pavlov

Picture of Georges M PavlovDr. Sci. Georges M. Pavlov studied physics at the State Leningrad University and received his master degree there in 1965. After two years working as a professor of physical sciences in Algeria, GMP began his scientific career at the Institute of Macromolecular Compounds of the USSR Academy of Sciences, where in 1975 he received his Ph.D. with V. N. Tsvetkov and S. Ya. Magarik for investigation on flow birefringence and hydrodynamic solution properties of homologous series of grafted copolymers. At the invitation of prof. V.N. Tsvetkov in 1977 GMP returned to the Department of Physics of the Leningrad State University, where later he was awarded a Dr. Sci. degree for his research on molecular hydrodynamics and optics of natural and synthetic polysaccharides. Pavlov has trained many undergraduates and doctoral students. His research activities are documented in over 200 scientific papers, focused on functional synthetic and biological macromolecular compounds, their properties, establishing the relationship between the chemical structure and corresponding properties of macromolecules. This includes investigation of polyelectrolytes in an extremely wide range of ionic strengths; macromolecules of complex topology (brush-shaped, star-shaped, dendrimer, hyperbranched, associated and supramolecular structures); influence of molecular characteristics of polymers on the properties of their films; methodology of molecular hydrodynamics (velocity sedimentation, translational diffusion, viscous flow of dilute solutions) and birefringence of polymer solutions and polymer films. During his career, he worked for a long time as an invited researcher in the Universities and Scientific Centers of UK, France, the Netherlands and Germany. Currently he is a Leading Researcher in the Institute of Macromolecular Compounds, Russian Academy of Science.

 What was your inspiration in becoming a polymer scientist?

When I was in high school, it was the time of the first sputniks/satellites (not to be confused with a vaccine), there was a lot of talk about the peaceful use of atomic energy. At school, I was more successful in natural science subjects (chemistry and physics) and mathematics. In the end, my choice fell on the Department of Physics of Leningrad University. At the University, when the choice of specialization came, I chose the Cathedra of Polymer Physics, at that time it was the only one in the USSR.

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

In collaboration with our chemist colleagues, at the Institute of Macromolecular Compounds, we investigate water-soluble amphiphilic polymer systems capable of retaining and transferring biologically active substances / drugs into a living organism. Such systems are prone to intra- and intermolecular association. It turned out that this ability can be detected by a well-known (routine ?!) method – by measuring the viscosity of dilute polymer solutions. However, two types of plots/equations of Huggins and Kremer should be applied in the interpretation of experimental data. So the tediousness/scrupulousness allowed this study to be done. Our recommendation is to use both plots in all cases of treating the viscometric data.

Which polymer scientist are you most inspired by?

This is a difficult question because we are known to stand on the shoulders of giants. With regard to polymer science, in particular the molecular physics of polymers, the pioneering fundamental work was done by Werner Kuhn, Paul Flory, Hermann Staudinger, Peter Debye. This list is far from complete, and the names can be arranged in a different order. But I would like to cite the name of Viktor N. Tsvetkov, who began to deal with issues of experimental molecular physics of polymers in the USSR, in particular, flow birefringence of polymer solutions at the beginning of the 40s of the 20th century. Later (in 1958), he organized the first in the USSR Cathedra of Polymer Physics at the Department of Physics of Leningrad University, which was equipped with a whole range of self-made precision devices for studying the molecular properties of macromolecules in solutions and films. His approach was to study the homologous series of different polymers using a complex of molecular hydrodynamics and optics methods, usually 4-5 different methods were used simultaneously. This Cathedra still exists under the name: Molecular Biophysics and Polymer Physics.

How do you spend your spare time?

Traveling, listening to different kinds of music.

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

Choosing a different path, I would choose something related to creativity. For example, I would to be a baker, but in France. However this extrapolation back in time is too long to be reliable and imaginable enough.

Read Georges’ full article now for FREE until 25 July

 


Detection and evaluation of polymer–polymer interactions in dilute solutions of associating polymers

An experimental tool for the evaluation of intramolecular associative/hydrophobic interactions in polymer/solvent systems was proposed and tested. The method is based on the measurements of the viscous flow in dilute polymer solutions and the analysis of the ln ηr vsc[η] dependence. This second derivative has a positive sign in the case of associating polymer or copolymer systems, and is negative for the non-associating ones. The value of the second derivative of this dependence may be used as a measure of the solvophobicity of polymer systems. Results obtained for three polymer systems: comb-like amphiphilic copolymers of N-methyl-N-vinyl acetamide and N-methyl-N-vinyl amine, brush-like copolymers of styrene and methyl methacrylate, and linear polystyrene, are presented and discussed.


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Saihu Liao

picture of Saihu Liao

Professor Saihu Liao

Prof. Saihu Liao studied chemistry at Huazhong University of Science and Technology, and obtained his bachelor degree in 2005. After two years of graduate study in Prof. Yuefa Gong’s group, he joined Prof. Benjamin List’s group at the Max-Planck-Institut for Coal Research (MPI-KOFO), Germany, as a PhD student, where he obtained his doctoral degree in organic chemistry in 2011. Then, he returned to China and joined Prof. Yong Tang’s group as a research associate at the Shanghai Institute of Organic Chemistry (SIOC), Chinese Academy of Sciences. In September 2016, he started his independent career at Fuzhou University, where he was promoted to full professor in 2017. Now, he is also the Director of the Key Laboratory of Molecule Synthesis and Function Discovery of Fujian Province Universities. His current research interests encompass photo-controlled polymerization, free radical chemistry, and organocatalysis.

 What was your inspiration in becoming a polymer chemist?

The idea to work on polymer chemistry for my own independent research came up when I was in Prof. Yong Tang’s group. There, I was impressed by the work on polyethylene chemistry: cheap ethylene can be converted into various and significantly different products like HDPE and highly branched oil by catalyst and ligand design. The power of control on a transformation is quite appealing. Another point attracted me is the polymer products that are often can be seen and touched. This reminded me of creating new stuff like toys by myself when I was very young.

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

The starting point of this work is to develop a ring-opening polymerization (ROP) of lactones that can be controlled (switch on-off) by light, when we have developed several photo-controlled radical polymerizations (Polym. Chem. 2019, 10, 6662; Nat. Commun. 2021, 12, 429). To reach a light regulation on polymerization based on a light-induced excited-state proton transfer mechanism is new, and there are many interesting things in this catalytic system, in particular the mechanistic aspects.

Which polymer scientist are you most inspired by?

Prof. Karl Ziegler, the previous director of the Max Planck Institute for Coal Research (Germany), and Prof. Yong Tang, my advisor at SIOC, they both inspired me to think about what kind of chemistry will make a big impact on our life in future, and also the responsibility as a scientist and a polymer chemist.

How do you spend your spare time?

When I have time, I prefer to play with my kids. If I need some relaxation, I will drive to the seashore and lie there for an afternoon to enjoy the blue and the clean sky.

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

If I was not a scientist, I would be an artist (installation artist?), probably a poor one. Then, I may need a part-time job.

 

Read Saihu’s full article now for FREE until 3 May

 


Visible light-regulated organocatalytic ring-opening polymerization of lactones by harnessing excited state acidity

Graphical abstract: Visible light-regulated organocatalytic ring-opening polymerization of lactones by harnessing excited state acidity

A visible light-regulated organocatalytic ring-opening polymerization of lactones has been developed by harnessing the excited state acidity of aromatic alcohol photocatalysts. Commercially available 1-hydroxypyrene (PyOH) is identified as an efficient organic photocatalyst, which afforded excellent control on the polymerization, a reversible activity mediation by light, and the well-defined polyester products with predictable molecule mass and narrow dispersity.


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Mona Semsarilar

Picture of Mona Semsarilar

Mona Semsarilar

Mona Semsarilar completed her MSc. in 2006 in physical chemistry under the supervision of Prof. E. Yilmaz (EMU, Cyprus). She continued her studies by joining Prof. S. Perrier’s team at the University of Leeds and earned her PhD from the University of Sydney in 2010, working on the synthesis of hybrid materials based on cellulose. She then moved to the University of Sheffield (UK) to work on Polymerisation-Induced Self-assembly (PISA) under the supervision of Prof. S. P. Armes (FRS). In 2015 she was recruited by the French national research organization (Centre National de la Recherche Scientifique – CNRS) as a research scientist based in the European Institute of Membranes (Institut Européen des Membranes – IEM) in Montpellier. In 2019, she received her habilitation from the University of Montpellier. Her research team looks into the preparation of materials primarily for applications in membrane and separation science using synthetic chemistry tools. Her current research focus on the design, synthesis and self-assembly of functional block copolymers, polymer-peptide conjugates, hybrid materials based on natural polymers, Metal Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs).

 

What was your inspiration in becoming a polymer chemist?

As a teenager, I was a big fan of Marie Curie as she was one of the only female figures in the world of Science and Technology. Also, my maternal great grandfather was a herbalist and I enjoyed going through his books and notes that my grandfather had inherited. I was fascinated by the hand-made illustrations and spent hours flicking through the fragile books and trying to copy the pictures! However, becoming a polymer chemist was just fortuitous. It just happened that I got a good offer to study polymer chemistry. I am deeply grateful for this coincidence as it paved my way into joining a family of great scientists that are not only good in what they do but also very kind and supportive individuals.

 

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

I have been working on the concept of Polymerisation-Induced Self-Assembly (PISA) since 2010. In the early years, we were mainly looking into two factors influencing the in-situ self-assembly; chemical functionalities in the shell-forming block and the solvophilic- solvophobic block ratios. One of our early works on galactose-coated nanoparticles prepared through PISA showed that hydrogen bonding played a crucial role in pushing the morphology towards higher orders. To explore this further, we wanted to use moieties that could provide a variety of supramolecular bonds and for this, peptides were the obvious choice. Now we have a library of monomers containing short sequences of peptides with ability to form hydrogen bonding and pi-pi interactions. Our first paper using these monomers, recently published in Macromolecules, demonstrates that presence of self-assembling peptides in the shell-forming block controls the self-assembly and is the main drive in the formation of interconnected fibrous networks. These results made it very clear that the presence of only few units of self-assembling peptide monomers were enough to push the self-assembly towards higher orders and form the unprecedented structures reported. For us the next obvious step was to see if the same effect could be seen once the self-assembling peptides were placed in the core of the particles, which is the subject of investigation in the current article.

 

Which polymer scientist are you most inspired by?

I have to say my two mentors (Prof. Perrier and Prof. Armes) have been a great source of inspiration for me. They are both brilliant minds, great scientists as well as very good managers. Their dedication and hard work towards science as well as their approach in managing their research team are admirable. They have a special way of making junior people fall in love with the science they do and create a sense of loyalty towards them and their team that is exceptional.

 

How do you spend your spare time?

Spare time?! What is spare time?!! Being mother of an energetic three years old does not leave any time to be spared!!! If by any chance I get a bit of time to myself (mainly while commuting) I would think chemistry! However, in the olden days (as Peppa Pig would say!) I used to enjoy reading.

 

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

I quite enjoy fine manual activities that require attention to details and precise skills. If not designing and making molecular structures, I would have enjoyed being a surgeon, tailor, carpenter or a silversmith. I also have a keen sense of observation and enjoy solving puzzles. So being a spy or a detective could have been the other options.

 

Read Mona’s full article now for FREE until 12th March

And if you are interested in reading more about PISA then check out our recent themed collection here all content is also free to read until 12th March

 


Nano-assemblies with core-forming hydrophobic polypeptide via polymerization-induced self-assembly (PISA)

graphical abstract

The aim of this study is to produce self-assembled structures with hydrophobic polypeptide cores via Reversible Addition–Fragmentation chain Transfer (RAFT) – mediated Polymerisation-Induced Self-Assembly (PISA). Hydrophilic poly(glycerol monomethacrylate) macromolecular chain transfer agents (PGMA mCTAs) were used to polymerize the self-assembling peptide monomers, resulting in the formation of diblock copolymer nano objects. Methacrylamide derivatives containing self-assembling tripeptides MAm-GFF (MAm-Gly-Phe-Phe-NH2) and MAm-FGD (MAm-Phe-Gly-Asp-NH2) were used as hydrophobic monomers. The self-assembling behaviours of these monomers mainly derive from the interactions of the phenylalanine residues, however their difference in hydrophobicity required different polymerization conditions. MAm-GFF was polymerized in the presence of organic solvent (ethanol or acetonitrile), under either dispersion or emulsion polymerization, while MAm-FGD was polymerized under aqueous dispersion conditions. PGMA-b-P(MAm-FGD) obtained from aqueous PISA typically formed fibrous structures while a range of morphologies such as fibre-, flake-, and leaf-like or spherical vesicles were obtained for PGMA-b-P(MAm-GFF) depending on the copolymer composition and solvent used. In all cases the peptides self-assembling core had a crucial influence on the final morphologies.

 


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Hans R. Kricheldorf

Hans R. Kricheldorf studied chemistry at the University of Freiburg im Breisgau where he obtained his master degree in 1967 and his PhD in 1969. He continued his academic career as assistant Professor at the “Institut für Makromolekulare Chemie” in Freiburg im Breisgau and achieved the tenure (Habilitation) in 1975 (awarded a prize by the Association of the German Chemical Industry). He was appointed Associate Professor at the same institute in 1980 and Full Professor of polymer chemistry at the University of Hamburg in 1982. He retired in 2008, but continued to perform experimental research without coworkers. His life-long working fields were ring-opening polymerization and polycondensation. During the past twenty years his interest was focused on syntheses of biodegradable polymers, interactions between ROP and polycondensation, and syntheses of cyclic and multicyclic polymers. He is author or coauthor of more than 800 peer-reviewed papers and patents and author, coauthor and/or editor of a dozen of books. Recently he was awarded the “Korshak Prize” of the Russian Academy of Sciences for his life-work on polycondensation.

What was your inspiration in becoming a polymer chemist?

My inspiration in becoming a polymer chemist had two sources. In the age of 15 I became interested in chemical experiments primarily in syntheses of explosives. In the age of 18 this hobby ended with a stay in a hospital, but at that time I was proud to have a collection of 27 different explosives. As a student I was mainly in organic chemistry, but when I had to select a research group for my PhD work, I decided for two reasons to enter the field of polymer chemistry. Firstly, I had the vision that there will be more space for fundamental research, because this part of chemistry was relatively new compared to organic and inorganic chemistry.  Secondly, the university of Freiburg im Breisgau with the Institut für Makromolekulare Chemie was a particularly attractive place to start a career in polymer chemistry, because the first Nobel Prize laureate in polymer science, Prof. H. Staudinger, had worked here for more than 30 years. When I was a young student I saw him twice one year before his death and he impressed me. I joined the group of Assoc. Prof. G. Greber (later Full Prof. and director at the Tech. Univ. of Vienna) who was the last PhD student of H. Staudinger. By joining his group, I became so-to-say a scientific grandson of H. Staudinger.

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

My motivation behind my recent work was an attempt to close two gaps in my knowledge about ring-opening polymerization of lactide (and lactones). For the technical production of poly(l-lactide) (meanwhile approaching 700 000 t/pa) tin(II) 2-ethlyhexanoate is the most widely used catalyst. For the technical production an alcohol is used as initiator to control the molecular weight and to accelerate the polymerization. However, over the past 20 years nobody has elucidated what happens in the absence of an initiator. Furthermore, I have recently defined and described a new type of polymerization called ROPPOC (ring-opening polymerization combined with simultaneous polycondensation). Introduction of a highly electrophilic and group via the catalyst is the key to success. However, catalysts introducing an anhydride group were still lacking in my collection of ROPPOC catalysts. The results obtained with Sn(II) acetate or 2-ethylhexanoate have now closed these gaps.

Which polymer scientist are you most inspired by?
My research activities of the past twenty years were mainly inspired by the work of Wallace H. Carothers, Paul J. Flory (Nobel Prize 1974) and Walter H. Stockmayer. These scientists formulated the experimental and theoretical fundament of step-growth polymerizations. However, when reading their papers, I had the impression that part of their theories, primarily their understanding of cyclization reactions, was incorrect. Therefore, I have spent much time and work with elaborating sufficient evidence for the correctness of my view. By the way, I became acquainted with both Flory and Stockmayer before 1985 and I was impressed by their personalities. But at that time, I had not worked yet on the aforementioned problems, so that our discussions touched other working fields.

How do you spend your spare time?

Forty years ago, I have begun to learn horse riding and over the past thirty years I had two horses. But recently I had to euthanize my second horse because of an accident, and now I’m to old to begin with a new horse. However, I continue to perform gym including bicycling and swimming to maintain my fitness as good as I can. Another major hobby is history, because any object and any idea has a history, and knowing more about the past means better understanding of the present. In this connection I have written several books after my retirement, for example a book about the most important 15 materials that form the fundament of our civilization, a book about history and philosophy of the natural sciences, a book about the history of polycondensation and most recently a book discussing the question, if life is the consequence of a chemical evolution.

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

I had chosen to become physician, probably specialized in radiology. In the aftermath I indeed regret that I have decided to study chemistry. In the years 1995-2010 I had a cooperation with Prof. Ch. Jürgens (surgeon and director at a big hospital in Hamburg) on applications of biodegradable films for dressing of large burn wounds and as tissue-separating films. Our films (mainly consisting of lactide) were commercialized under the trade marks “Topkin” and “Mesofol “, but the Merck-Biomet company which produced  these films stopped the production after ten years for financial reasons, and thus, our films did not become a big success. Nonetheless, our films supported an almost painless healing of more than 500 patients. From this cooperation I have learned that it is more satisfactory for me to help patients to recover from their wounds than publishing several more papers on polymer chemistry.

 

Read Hans’ full article now

 


 

High molar mass cyclic poly(l-lactide) obtained by means of neat tin(ii) 2-ethylhexanoate

Hans R. Kricheldorf  and  Steffen M. Weidner

L-Lactide was polymerized in bulk at 120, 140, 160 and 180 °C with neat tin(II) 2-ethylhexanoate (SnOct2) as the catalyst. At 180 °C the Lac/Cat ratio was varied from 25/1 up to 8000/1 and at 160 °C from 25/1 up to 6000/1. The vast majority of the resulting polylactides consist of cycles in combination with a small fraction of linear chains having one octanoate and one COOH end group. The linear chains almost vanished at high Lac/Cat ratios, as evidenced by MALDI-TOF mass spectrometry and measurements of intrinsic viscosities and dn/dc values. At Lac/Cat ratios <1000/1 the number average molar masses (Mn) are far higher than expected for stoichiometic initiation, and above 400/1 the molar masses vary relatively little with the Lac/Cat ratio. At 180 °C slight discoloration even at short times and degradation of the molar masses were observed, but at 160 °C or below colorless products with weight average molar masses (Mw) up to 310 000 g mol−1 were obtained. The formation of high molar mass cyclic polylactides is explained by a ROPPOC (Ring-Opening Polymerizatiom with simultaneous Polycondensation) mechanism with intermediate formation of linear chains having one Sn–O–CH end group and one mixed anhydride end group. Additional experiments with tin(II)acetate as the catalyst confirm this interpretation. These findings together with the detection of several transesterification mechanisms confirm the previous critique of the Jacobson–Stockmayer theory.

 


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Jiangtao (Jason) Xu

Dr. Jason Xu is an Australian Research Council (ARC) Future Fellow at School of Chemical Engineering, UNSW Sydney. He is currently leading a research group in the Cluster for Advanced Macromolecular Design (CAMD) and Australian Centre for NanoMedicine (ACN), with the focus on green and precision polymer synthesis using state-of-the-art polymerization techniques and organic chemistry tools. Dr. Xu received his BS and PhD Degrees (2007) in Polymer Chemistry from Fudan University. Following post-doctoral research in UNSW and University of Melbourne and industrial experience, he joined UNSW to develop visible light-induced living polymerization and precision polymer synthesis. He has more than 100 peer-reviewed publications in high-impact journals, attracting over 6300 citations and an h-index of 45. His areas of research interests are green chemistry and sustainable polymer synthesis, precision polymer synthesis mimicking natural perfection, advanced polymer hydrogels for strain and bio-sensors.

What was your inspiration in becoming a polymer chemist?

When I was still a freshman in the university, polymer chemistry was still a young and rising area at the end of 20th century in China, full of mysteries and possibilities. I was inspired by a lecture delivered by a professor in our school who is one of the pioneering researchers in polymer chemistry. He presented the amazing properties of liquid crystal polymers and foreseeable future of these materials. After that, I started to learn more about polymers and I knew polymers have already been everywhere in our life, plastics and rubbers and synthetic resins. However, there are still many things unknown for polymers, particularly for polymer chemistry. How to design and synthesize these gigantic molecules with the properties we want? This is the question, from then on, always in my mind.

What was the motivation behind your most recent Polymer Chemistry article in the Pioneering Investigators collection?
Natural biopolymers (DNA and peptides) have uniform microstructures with defined molecular weight and precise monomer sequence along the polymer chain that affords them unique biological functions. To reproduce such structurally perfect polymers through chemical approaches, researchers have proposed using synthetic polymers as an alternative. Different methodologies have been developed in the last decades. We recently proposed an emerging technology of single unit monomer insertion (SUMI), which is very similar to peptide synthesis from amino acids. SUMI can precisely prepare uniform and monodisperse alternating polymers using sequential addition of two monomers. However, the characterization of precision structure is getting harder and harder while the polymer chain increases. We therefore propose a series of short oligomers with three monomer units (trimers) to model the reaction for each step. These model trimers can provide the detailed reaction kinetics and mechanism as well as product yields, which will be the same as the reactions in long chain polymer synthesis due to the repeating monomer additions. These model trimers can also provide the reaction kinetics for copolymerization of corresponding monomers.

Which polymer scientist are you most inspired by?
There are many excellent polymer scientists I was most inspired by, such as Professors Craig Hawker and Masami Kamigaito in my mind as examples. Craig is full of very useful and bright ideas covering broad polymer area in chemistry and materials. Our recent photopolymerization technology of PET-RAFT is inspired by his pioneering work in 2012. Masami is at the forefront of polymer synthesis. His work in green polymer synthesis using renewable monomers from natural plants is fascinating.

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

This is an interesting but difficult-to-answer question. From my point of view in the specific field of polymer synthesis, there are many young and smart researchers whose research is believed to have a big impact, such as Professors Brett Fors (Cornell) and Athina Anastasaki (ETH) as examples. Their recent excellent works in photocontrolled cationic polymerization and precise polymer dispersity control are good evidence to demonstrate their potential to impact the field. Their contribution will push forward the field of polymer synthesis.

How do you spend your spare time?
I spend my spare time with my family to go out for BBQ and hiking. My daughter is currently two years old, which requires a lot of accompanying and brings so much fun to my life. Also, I like very much playing badminton and have been playing for more than 15 years. It is one of my favorite sports because it is free of any body contact different from basketball or soccer, but still requires the strength, balance and motion skills. It is therefore one of the sports anyone can keep for their whole life.

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

I would choose my profession to be an automotive mechanic. Auto mechanic is a “precision” job like a doctor. It requires to know how all different auto parts been designed and how they work synergistically, which enables to quickly diagnose and fix the mechanical malfunction. As a mechanic, the body and mind will work all the time, which can keep the mind sharp and the body active and healthy. Actually, I hold a TAFE Auto mechanic certificate and always had a plan to run a workshop. What I need now is the financial support from some potential investors (kidding!).

Read Jason’s full article now for FREE until 17 November!

Also check our the work of our other Pioneering Investigators here

 


Sequential and alternating RAFT single unit monomer insertion: model trimers as the guide for discrete oligomer synthesis

Graphical abstract: Sequential and alternating RAFT single unit monomer insertion: model trimers as the guide for discrete oligomer synthesis

Sequence-defined polymers have garnered increasing attention in a broad range of applications from materials engineering to medical science. Reversible addition–fragmentation chain transfer single unit monomer insertion (RAFT SUMI) technology has recently emerged as a powerful tool for sequence-defined polymer synthesis, which utilizes sequential monomer radical additions occurring one unit at a time to assemble olefins into uniform polymers. The strategy of employing alternating additions of electron-donor and acceptor (D–A) monomers can be used to prepare long chain sequence-defined polymers by the RAFT SUMI technique. However, considering both terminal and penultimate unit effects, complex radical reaction kinetics can result from various monomer addition orders particularly if three or more different families of vinyl monomers are used to build diverse sequences. Simplifying reaction processes and establishing reaction kinetics will be critical for effective synthesis of sequence-defined polymers. Herein, a series of model trimers containing D–A–D and A–D–A triads was thus produced from four families of α,β-disubstituted vinyl monomers (N-phenylmaleimide, fumaronitrile and dimethyl fumarate and indene). Such trimers presented distinct synthesis kinetics (reaction rate and yield). These model trimers and their kinetics data are able to provide full guidance for the synthesis of long chain discrete polymers using sequential and alternating RAFT SUMI processes.


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Urara Hasegawa

Urara Hasegawa received her B.S. and M.Eng. in Applied Chemistry from Waseda University (Japan). She earned her Ph.D. in Biomedical Science from Tokyo Medical and Dental University (Japan) under the supervision of Professor Kazunari Akiyoshi. Then, she worked as a postdoctoral fellow in the lab of Professor Jeffrey Hubbell at École Polytechnique Fédérale de Lausanne (EPFL) (Switzerland). She joined the Department of Applied Chemistry at Osaka University (Japan) as an assistant professor in 2011, and then moved to the Department of Chemical Engineering at Kansas State University in 2017. In 2020, she joined the Department of Materials Science and Engineering at Pennsylvania State University. Her research focuses on development of polymeric nanomaterials for controlled delivery of drugs and bioactive signaling molecules. She has published more than 45 peer-review papers and has received several awards including a NSF CAREER award in 2020.

 

What was your inspiration in becoming a polymer chemist?

When I was an undergraduate student, I had the opportunity to learn about cell sheet engineering developed by Professor Teruo Okano at Tokyo Women’s Medical University. They used surfaces coated with poly(N-isopropyl acrylamide) (PNIPAM) as a temperature-responsive tissue culture plate, which enables to harvest cultured cells by lowering temperature below the lower critical solution temperature of PNIPAM. This technology solved the problems associated with conventional techniques requiring a proteolytic enzyme to detach cells. I was excited to see how synthetic polymers can be used to manipulate living cells. Since then, I have developed a strong interest in polymer chemistry that can contribute to the advance of biomedical technologies.

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

I’m particularly interested in gaseous signaling molecules (gasotransmitters) such as nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S), which are generated ubiquitously in our body and serve as essential signaling regulators in many physiological and pathological processes. One of the challenges in gasotransmitter research is the lack of delivery technologies, which enable the delivery of a known amount of gasotransmitter for a specific period of time to target cells and tissues. So far, significant efforts have been made to develop small gas donor compounds that decompose to generate gasotransmitters under physiological conditions. However, the use of these compounds is limited due to the fast and uncontrolled gas release rate and toxic side effects of the donor compounds and/or their decomposition byproducts.

In the past years, my research group has been focused on developing polymeric micelles for delivery of NO, CO and H2S to cells. We have been successful in showing the advantages of using polymeric micelles for gasotransmitter delivery by slowing down release rate, reducing toxic side effects and improving therapeutic efficacy. In the recent Polymer Chemistry article, we demonstrated that H2S release rate from polymeric micelles can be modulated by controlling micellar stability, which significantly affects proangiogenic activity of these H2S-releasing micelles. The developed technology will be used as a delivery tool to enhance the fundamental understanding of H2S biology, which will lead to development of innovative approaches for the prevention and treatment of a variety of diseases.

Which polymer scientist are you most inspired by?

Although there are so many remarkable researchers in the field of polymeric biomaterials science, Professor Helmut Ringsdorf at University of Mainz and Professor Jindřich Kopeček at University of Utah are the researchers who I’m inspired by. They developed the concept of “polymer-drug conjugate” in the mid 1970’s to improve solubility and blood circulation time of drugs as well as confer targeting capability. Another researcher who influenced my work is Professor Kazunori Kataoka at University of Tokyo. He is the pioneer of polymeric micelles for drug delivery.

How do you spend your spare time?
I enjoy spending time with my cats. I like to see them sleeping in the most cozy and comfortable spots in the house and hear them purring when I’m patting them. I also love visiting different places and enjoy local foods and cultures. I recently found a new hobby: Origami (Japanese style paper folding). This is a good way to relax and refresh my mind.

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

I still would like to choose a job related to science. A graphic designer for scientific illustration could be a profession I would be interested in. I feel graphics are a powerful tool to explain the essence and concepts of research and increase impact of new technologies and scientific findings. I love to draw and would enjoy contributing to science even if I were not a scientist.

Read Urara’s full article now for FREE until 8 October

 


Hydrogen sulfide-releasing micelles for promoting angiogenesis


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Trang N. T. Phan

Trang N. T. Phan is an Associate Professor in the Institute of Radical Chemistry at Aix-Marseille University in France. She completed her undergraduate studies with a Masters in chemistry and then joined the PhD program in Polymers and Organic Chemistry at University of Lille 1. She received her PhD in 2000 under the supervision of Pr. M. Morcellet. During her PhD at the Macromolecular Chemistry Lab, she worked on the synthesis, characterization and water purification application of sorbents based on silica gel functionalized with β-cyclodextrin based polymers. During 2000-2002, she worked as a postdoctoral researcher at the Materials and Interfaces Chemistry Lab of University of Franche-Comté, first in the European project SILACOR and then in a project with BASF on the adsorption of polyelectrolytes on zinc oxide nanoparticles. In 2002, she joined Pr Denis Bertin’s group, firstly as a temporary lecturer and then as a postdoctoral researcher. In September 2004, she became a full associate professor at Aix-Marseille University in the group of Didier Gigmes. In 2014, she received with her colleagues (R. Bouchet and D. Gigmes) the International Prize EDF PULSE Science and Electricity. Her current research interests are in the design and the synthesis of advanced functional polymers via controlled polymerization techniques for specific applications such as solid polymer electrolytes, polymers blend compatibilizers and structure-directing agents.

 

What was your inspiration in becoming a polymer chemist?

During my Bachelors course work and internship project, I started learning about polymer chemistry. I was fascinated by the “magic” of the transformation of small molecules (monomers) to polymers which are useful functional materials. From that moment, I decided to learn more about how chemistry can help to design and synthesize (co)polymers with precise structure, functionality and composition responding to desired properties and specific applications.

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

Radical ring-opening polymerization (rROP) of cyclic monomers is an attractive method to synthesize functional polymers bearing both heteroatoms in the backbone and functional groups in the side chain. In addition, the potential applicability of rROPs for copolymerizations with vinyl monomers is a highly attractive feature. Among different cyclic monomers, vinyl cyclopropane (VCP) derivatives were the most promising compounds since their rROPs led to low-shrinkage materials with attractive applications for dental adhesives and composites. However, functional groups in the side chain of VCP polymers are usually limited to halogens, esters and nitrile functions that restrict the development of new functional VCP polymers by post-polymerization modification. During our investigation of new VCP derivatives, we have achieved a straightforward pathway for the synthesis of VCP bearing azlactone functionality. The azlactone group can react via rapid and efficient ring-opening reactions with different nucleophilic species such as primary amines, hydroxyls, and thiols. We expect that the new VCP-azlactone (co)polymers could serve widely as a reactive platform for the introduction of chemical and biological functionality.

Which polymer scientist are you most inspired by?

I am greatly interested by the work being undertaken in the group of Pr. David Mecerreyes since their research allies polymer chemistry, supramolecular chemistry and nanomaterials science to synthesize innovative polymeric materials.

How do you spend your spare time?
I like cooking and experimenting with new recipes by combining western and oriental flavors. After all, cooking is similar to chemistry. I also like hiking and reading.

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

I’d be a Scuba dive master practicing somewhere in the warm waters of tropical seas.

Read Trang’s full article now for FREE

 


Radical ring-opening polymerization of novel azlactone-functionalized vinyl cyclopropanes

Azlactone-functionalized polymers are considered powerful materials for bioconjugation and many other applications. However, the limited number of azlactone monomers available and their multistage syntheses pose major challenges for the preparation of new reactive polymers from these monomers. In this article, we report the synthesis of a new class of azlactone monomers based on vinylcyclopropane (VCP). Furthermore, the (co)polymerization of the azlactone-functionalized VCPs has been successfully demonstrated to provide new azlactone polymers by using free-radical polymerization. The ability of the resulting amine-reactive polymers to be engaged in post-polymerization modifications was demonstrated using dansylcadaverine. These new azlactone-functionalized VCP monomers and polymers are potential candidates for the synthesis of innovative (bio)materials.


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Nicholas J. Warren

Nick WarrenNick Warren  is a University Academic Fellow within the School of Chemical and Process Engineering at the University of Leeds. He was awarded an Masters in Chemistry from the University of Bristol in 2005 following which he conducted two years industrial research. He then moved to the University of Sheffield where he studied for a PhD in Polymer Chemistry within Prof Steve Armes’ research group where he focussed on synthesis of biocompatible block copolymers. Following his PhD, he continued as a postdoctoral researcher in Sheffield working in the area of polymerisation-induced self-assembly (PISA) until 2016, when he moved to Leeds to start his independent research career. His current research aims to exploit the latest advances in polymerisation techniques, combined with new reactor technologies for the design and discovery of controlled-structure polymers.

What was your inspiration in becoming a polymer chemist?

During my undergraduate masters project, I worked on development on combining pH responsive microgels with photo-responsive surfactants. I was fascinated by the ability to use chemical composition as a means of tuning physical characteristics of a material and imparting responsive behaviour. This brought on a specific interest in synthetic polymer chemistry, where there are so many synthetic routes to generating responsive materials. This was the focus of my PhD, where I gained expertise in ATRP and RAFT polymerisation which provided a convenient tool-box allowing me to design and synthesise pH responsive block copolymers.

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

Continuous-flow techniques are well utilised in small molecule synthesis and are now becoming commonplace in polymer chemistry. In my research group, we aim to use flow-chemistry to conduct polymer synthesis and try and exploit its characteristics to develop new materials, streamline methods for optimising polymerisation processes; or for detailed online monitoring. We have already published some work conducting PISA in flow, which combined my existing expertise in PISA, with my growing interest in reactor technologies, but it became apparent that the relatively long timescales for the reactions meant that there were limited advantages over batch synthesis. We therefore looked to speed up the process, which was relatively straight-forward since our all-acrylamide PISA system was ideally suited to Seb Perrier’s ‘ultrafast’ RAFT technology. By using flow-reactors equipped with online monitoring, we were not only able to synthesise a wide range of PISA nanoparticles on short timescales, but also obtain kinetic data despite the short reaction time.

Which polymer scientist are you most inspired by?

From a synthetic perspective, the work being undertaken in Prof Brent Sumerlin’s group encompasses many of the areas I have a keen interest. I am also inspired by Prof Tanja Junkersresearch, since she is at the forefront of work into applying automation and flow chemistry to polymer synthesis.

How do you spend your spare time?

I now have two children under 3, so I spend most of my time running around after them! We spend quite a lot of time hiking in the Peak District and I also like to cook, which has recently expanded into bread making (to varying degrees of success).

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

I’d be a barista with a small coffee shop somewhere sunny.

Read Nick’s full article now for FREE

And if you are interested in reading more about PISA then check out our recent themed collection here


Rapid production of block copolymer nano-objects via continuous-flow ultrafast RAFT dispersion polymerisation

 

graphical abstract

Ultrafast RAFT polymerisation is exploited under dispersion polymerisation conditions for the synthesis of poly(dimethylacrylamide)-b-poly(diacetoneacrylamide) (PDMAmxb-PDAAmy) diblock copolymer nanoparticles. This process is conducted within continuous-flow reactors, which are well suited to fast reactions and can easily dissipate exotherms making the process potentially scalable. Transient kinetic profiles obtained in-line via low-field flow nuclear magnetic resonance spectroscopy (flow-NMR) confirmed the rapid rate of polymerisation whilst still maintaining pseudo first order kinetics. Gel permeation chromatography (GPC) reported molar mass dispersities, Đ < 1.3 for a series of PDMAmxb-PDAAmy diblock copolymers (x = 46, or 113; y = 50, 75, 100, 150 and 200) confirming control over molecular weight was maintained. Particle characterisation by dynamic light scattering (DLS) and transmission electron microscopy (TEM) indicated successful preparation of spheres and a majority worm phase at 90 °C but the formation of vesicular morphologies was only possible at 70 °C. To maintain the rapid rate of reaction at this lower temperature, initiator concentration was increased which was also required to overcome the gradual ingress of oxygen into the PFA tubing which was quenching the reaction at low radical concentrations. Ill-defined morphologies observed at PDAAm DPs close to the worm-vesicle boundary, combined with a peak in molar mass dispersity suggested poor mixing prevented an efficient morphological transition for these samples. However, by targeting higher PDAAm DPs, the additional monomer present during the transition plasticises the chains to facilitate formation of vesicles at PDAAm DPs of ≥300.


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Suhrit Ghosh

Suhrit Ghosh was born in 1976 in India. After the completion of his undergraduate education (Chemistry major) at the Presidency College (now University), Kolkata, he was admitted to the integrated PhD program (Chemical Science) at the Indian Institute of Science, Bangalore in 1997. He received his MS degree (Chemistry) in 2000 and continued for PhD until 2005 under the supervision of Professor S. Ramakrishnan. Then he moved to the group of Professor S. Thayumanavan at the University of Massachusetts, Amherst, USA, for postdoctoral studies (2005-2007). Subsequently he worked as an Alexander von Humboldt postdoctoral fellow (2007-2008) with Professor Frank Würthner at the University of Würzburg, Germany. In 2008 he joined the Indian Association for the Cultivation of Science (IACS), Kolkata, India, as an Assistant Professor where he currently holds the position of Professor and Chair of the School of Applied and Interdisciplinary Sciences.

Research interests of his group include supramolecular polymerization of donor-acceptor π-systems, H-bonding driven directional assembly of amphiphilic π-systems/macromolecules and biologically relevant stimuli responsive aggregation of amphiphilic polymers (polydisulfides, polyurethanes). He has about 100 publications in peer reviewed journals and ten PhD students have graduated from his group. He is the recipient of the B. M. Birla Science Prize in Chemistry (2014), JSPS Invitation Fellowship (long term) Japan (2014), SwarnaJayanti Fellowship (2015) from the Department of Science and Technology, Government of India, K. Kishore Memorial Award (2016) from the Society of Polymer Science, India and the Bronze medal (2017) from the Chemical Research Society of India. He has been serving as an Associate Editor for the journal RSC Advances since 2015.

What was your inspiration in becoming a polymer chemist?

I was introduced to Polymer Chemistry by two captivating teachers (Professor Manas Chanda and Professor S. Ramakrishnan) during my Master’s Degree course work in the Indian Institute of Science, Bangalore. Subsequently I had an opportunity to carry out a year-long MS project on Polymer Chemistry under the supervision of Professor S. Ramakrishnan when I started learning more about the subject. From group discussions and seminars in the department, I learnt about the emerging topics (of the time) in Polymer Chemistry such as foldamers, molecular imprinting, conjugated polymers, helical polymers, amphiphilic polymers, supramolecular polymers and so on. I was greatly inspired by such diversity in the field and its interdisciplinary nature connecting chemistry with biology and materials science.

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

Poly(disulfide)s (PDS), although known for long time, lacked structural diversity in the absence of any generally applicable synthetic methodology. Recently we had established a mild step-growth polymerization approach to make linear functional PDS by a facile thiol-disulfide exchange reaction between commercially available 2,2′-dipyridyldisulfide and a di-thiol.  By taking a stoichiometric excess of the first monomer, telechelic PDS could be prepared with the reactive pyridyl-disulfide groups at the chain terminal which could be further functionalized by a functional thiol without disturbing the backbone disulfide groups. This motivated us to extend this approach for the synthesis of hyperbranched PDS, particularly considering the possibility of decorating such hyperbranched polymers with multiple reactive pyridyl-disulfide groups at the periphery for post-polymerization functionalization to produce a range of functional hyperbranched polymers with a fully bio-reducible disulfide backbone. We have exactly demonstrated this in our recent Polymer Chemistry paper and envisage that it might allow the screening of structurally diverse amphiphilic hyperbranched PDS for biological applications such as drug delivery.

Which polymer scientist are you most inspired by?

I am most inspired by Professor E. W. Meijer (Eindhoven University of Technology, The Netherlands), especially because of his pioneering fundamental contribution in the field of supramolecular polymers by connecting supramolecular chemistry and polymer chemistry.

How do you spend your spare time?

I like to cook, spend time with my 10-year-old daughter and socialize with like-minded people.

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

Practising literature and creative writing.

Read Suhrit’s full article now for FREE until 8th May!


Hyperbranched polydisulfides

Disulfide containing polymers have been extensively studied as responsive materials for biomedical applications such as drug delivery, gene delivery, bio-sensing and receptor-mediated cellular uptake due to the possibility of cleaving the disulfide linkage with glutathione (GSH), a tri-peptide overexpressed in cancer cells. While linear and branched polymers containing disulfide groups have been already studied and more recently polydisulfides (PDS) have come to the fore, hyperbranched polydisulfides (HBPDS) were not known. This manuscript for the first time reports a generally applicable methodology for the synthesis of HBPDS by an A2 + B3 condensation approach. The B3 monomer contains three pyridyl-disulfide (Py–Ds) groups while a di-thiol compound serves as the A2 monomer. A polycondensation reaction under very mild reaction conditions produces HBPDS (Mw = 14300 g mol−1Đ = 1.9) with a very high degree of branching (DB) value of 0.8 and more than twenty highly reactive Py–Ds groups present at the terminal or linear unit of a polymer on an average. The reactive Py–Ds groups can be completely replaced by post-polymerization functionalization using a hydrophilic thiol resulting in bio-reducible amphiphilic HBPDS. It produces micellar aggregates in water with a hydrodynamic diameter of ∼80 nm, a low critical aggregation concentration (7.0 μM) and a high dye (Nile red) loading content. The exchange dynamics of these micellar aggregates, studied by fluorescence resonance energy transfer (FRET), reveals practically no inter-micellar exchange after 6 h indicating very high non-covalent encapsulation stability. On the other hand, in the presence of glutathione, the PDS backbone can be degraded resulting in an efficient triggered release of the encapsulated dye. Dye release kinetics strongly depends on the GSH concentration and interestingly with a fixed concentration of glutathione the release kinetics appears to be much faster for the hyperbranched PDS micelle compared to its linear analogue. MTT assay with two representative cell lines indicates that the amphiphilic HBPDS is biocompatible up to 500 μg mL−1 which is further supported by hemolysis assay showing merely 6.0% hemolysis up to a polymer concentration of 500 μg mL−1.


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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Polymer Chemistry Author of the Month: Stefan A F Bon

Professor Stefan A. F. Bon

Stefan A. F. Bon is a full professor in the Department of Chemistry at the University of Warwick in the United Kingdom. He studied chemical engineering at the Eindhoven University of Technology (TUe) in the Netherlands (cum laude, 1989-1993), where he also did his Ph.D. (1993-1998) in the polymer chemistry group of prof.dr.ir. Anton L. German. In April 1998 he moved to the UK  where worked as a post-doctoral research assistant in the group of prof. David M. Haddleton at the University of Warwick (1998-2000). He was appointed as Unilever Lecturer in Polymer Chemistry at the University of Warwick in January 2001. During this period of research he focused on the mechanistic aspects of living radical polymerisation in both homogeneous and heterogeneous systems, including the first ever living radical polymerization performed in emulsion. From 2005 Stefan Bon shifted his research interests from living radical polymerization to supracolloidal chemical engineering. Current research focuses on the design of assembled supracolloidal structures and the synthesis of their colloidal and macromolecular building blocks through combination of polymer chemistry, colloid science, soft matter physics, and chemical engineering. Check out www.bonlab.info for more.

What was your inspiration in becoming a polymer chemist?

Eindhoven University of Technology in the 1990s was a fantastic place for polymer science, especially in the fields of emulsion polymerization and polymer physics and processing. We had captivating teachers, such as Alex van Herk, Anton German, and Piet Lemstra.  I was fascinated by it all as an undergrad student and hooked after my international internship at Nippon Paint where I worked on polymer colloids in the summer of 1992. I grabbed the opportunity to do my PhD on nitroxide mediated polymerizations at the end of 1993. What I love about polymer and colloid science is that you can blend chemistry, with physics, mathematics and engineering, fading out boundaries between classical disciplines.

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

In the mid 2000s we started applying the phenomenon of Pickering stabilization, the concept that particles can adhere to soft deformable interfaces, to mini-emulsion and emulsion polymerization processes. In the last decade we tried to come to a full mechanistic understanding of emulsion polymerization processes in which nanoparticles played the role of molecular surfactants. For the most part we focussed on inorganic nanoparticles, such as clay and silica sols. In 2018/2019 we asked ourselves if Pickering emulsion polymerization would be possible using polymer nanoparticles (10-40 nm), that is nanogels or crosslinked polymer micelles could be used instead. To our delight we found that using nanogels gave us the opportunity to control the morphology of the polymer colloids produced by the Pickering emulsion process. Janus, patchy and armored particles can be made. We wanted to unravel the exact mechanism. The paper in Polymer Chemistry describes a detailed mechanistic study on the effect of inert electrolyte (salt) on the emulsion polymerization process.

Which polymer scientist are you most inspired by?

On passion for emulsion polymerization I would like to mention Bob Gilbert. I know Bob since the mid 1990s, and have great respect for him. I still remember the discussions we had at Santa Margherita Ligure in 1996 on kinetics of radical polymerization and life. I love his mechanistic/kinetic approach to describe scientific concepts and have adopted this as a way of working in my team. On optimism and living larger than life, my former polymer chemistry teacher and friend Alex van Herk, who now works at A*STAR in Singapore. A big thank you to both.

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

Restricting myself to people with an academic career path I would like to mention four: Nick Ballard (POLYMAT, Spain), Athina Anastasaki (ETH Zürich, Switzerland), Stuart Thickett (UTAS, Australia), and Zhihong Nie (Fudan University, China). Why? That is simple, all four are fantastic.

How do you spend your spare time?

My husband and I bought a house in Coventry (UK) a bit over a year ago, and since then the garden is undergoing a transformation to see how many different plants we can put into the space. I think soon we will run out of space and there won’t be a single bit of traditional British lawn left. We like to cook (Chinese/Dutch fusion) , travel, and go to the theatre/concerts. We are looking forward to seeing Pink Martini soon in Birmingham. Will pick up playing the guitar again (haha, and if you wonder what style of music: Julio Iglesias of course!).

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

That is a hard question. Has to be creative and with people for sure. May be something in the area of people communication/management mediation..

Read Stefan’s full article now for FREE until the 31st March!


Effect of the addition of salt to Pickering emulsion polymerizations using polymeric nanogels as stabilizers

Graphical abstract: Effect of the addition of salt to Pickering emulsion polymerizations using polymeric nanogels as stabilizers

Nanogels made from crosslinked block copolymer micelles are used as stabilizers in the Pickering emulsion polymerization of styrene. The effect of the addition of salt, i.e. NaCl, on the emulsion polymerization is studied. It is shown that an increase in ionic strength of the dispersing medium in these polymerizations led to the formation of latexes of larger diameters. Along with an increase in size, the morphology of these polymer colloids changed from Janus to patchy with an increase in number of nanogels adsorbed on the polymer surface, as a function of the salt concentration in water. In particular, at the highest tested ionic strength, ca. 25 mM, fully armored polymeric particles surrounded by a dense layer of adsorbed stabilizing nanogels were formed. Kinetic studies carried out at varying NaCl concentrations suggested that particle formation in the reaction followed a combination of a coagulative nucleation mechanism, characterized by a clustering process of Janus precursors to form bigger aggregates, and droplet nucleation. Preliminary film formation studies on latexes made with n-butyl acrylate as a comonomer indicated the potential of this technique for the production of coherent polymer films which included a substructure of functional nanogels.


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based at the Laboratoire de la Chimie des Polymères Organiques (LCPO) in Bordeaux, France. 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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