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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2021 Polymer Chemistry Lectureship awarded to Brett Fors

It is with great pleasure that we announce Brett Fors (Cornell University) as the recipient of the 2021 Polymer Chemistry lectureship.

This award, now in its seventh year, honours an early-career researcher who has made significant contribution to the polymers field. The recipient is selected by the Polymer Chemistry Science Editorial Board from a list of candidates nominated by the community.

Promotional image of Brett Fors as 2021 Polymer Chemistry lectureship winner

Brett P. Fors was born in Montana and carried out his undergraduate studies in chemistry at Montana State University (2006). He went on to do his Ph.D. (2011) at the Massachusetts Institute of Technology with Professor Stephen L. Buchwald. After his doctoral studies he became an Elings Fellow at the University of California, Santa Barbara working with Professor Craig J. Hawker.  In of 2014 he joined the faculty at Cornell University and is currently an Associate Professor in the Department of Chemistry and Chemical Biology. His group’s research focuses on the development and application of new synthetic methods for polymer science. He and his group can be found on Twitter @brett_fors and @forsgroup.

 

Polymer Chemistry Editor-in-Chief, Christopher Barner-Kowollik, says that Prof. Fors is a leader in the development of advanced (photochemical) synthetic methods, fusing elegant new concepts of organic chemistry with advanced polymer materials design. His research is seminal and inspiring to our community. I am delighted that the 2021 Polymer Chemistry Lectureship is awarded to Brett, a true ambassador of polymer science excellence.

 

Read Brett’s latest article in Polymer Chemistry Achieving molecular weight distribution shape control and broad dispersities using RAFT polymerizations” and all of his other publications in Polymer Chemistry for FREE until 1 August. These and articles from our previous lectureship winners can be found in our lectureship winners collection.

 

How has your research evolved from your first article to the most recent article?

Our research program has evolved to a point that I would not have imagined when our group was getting started–this is a result of having very talented co-workers and collaborators that have taken our research in directions that I could not have predicted.

 

What excites you most about your area of research and what has been the most exciting moment of your career so far?

Results that change our understanding of a system are especially exciting to me. The most exciting moments of my career have been seeing my students develop and succeed as scientists.

 

In your opinion, what are the most important questions to be asked/answered in your field of research?

In my opinion the most important questions being asked in a field are not obvious.  I strongly believe that continuing to encourage high quality basic research in the area of polymer chemistry is what is important.  However, if I was to pick one area that I believe will have an impact on society it would be developing sustainable polymer systems.

 

How do you feel about Polymer Chemistry as a place to publish research on this topic?

Polymer Chemistry is an excellent platform to publish high quality studies and is one of my favorite journals to read and keep up with the current field of polymer science.

 

Which of your Polymer Chemistry publications are you most proud of and why?

I cannot choose – I am very proud of all of the work and creativity that my co-workers put into all of our Polymer Chemistry publications.

 

In which upcoming conference or events (online or in person) may our readers meet you?

With Covid I am currently unsure as conferences are continually being moved but I will definitely be at Pacifichem.

 

Can you share one piece of career-related advice or wisdom with early career scientists?

My one piece of advice is to work in an area that you are passionate about and don’t forget to enjoy the process of research.

 

How do you spend your spare time?

I spend my free time with my wife and two kids!

 

We would like to thank everybody who nominated a candidate for the 2021 Polymer Chemistry Lectureship. The Editorial Board had a very difficult task in choosing a winner from the many excellent and worthy candidates.

 

Please join us in congratulating Brett on winning this award!

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Paper of the month: Synthesis, characterization and self-assembly of linear and miktoarm star copolymers of exclusively immiscible polydienes

Ntetsikas et al. synthesised a series of linear and miktoarm star copolymers to study their self-assembly behaviour in bulk.

Block copolymers consisting of high 1,4-microstructure-content polybutadiene (PB1,4) blocks  and high 3,4-content polyisoprene (PB1,4b-PI3,4) blocks self-assemble, due to their incompatibility, to form different nanostructures useful for various applications, such as electronic devices, nanotechnology and optoelectronics. In this work, Avgeropoulos and co-workers report a new synthetic procedure for the preparation of four linear PB1,4b-PI3,4 diblock copolymers and eight asymmetric miktoarm star copolymers and investigate the effect of the architecture (linear versus non-linear) on microphase separation and final nanostructure of these copolymers. Furthermore, the results of this study have been compared with the PS(PI1,4)n (PS: polystyrene) well studied and established systems.

In particular, the authors combined anionic polymerization and selective chlorosilane chemistry to prepare four different sets of linear and star copolymers. Each set included one linear diblock copolymer with similar molecular characteristics to the corresponding PB1,4(PI3,4)2 and PB1,4(PI3,4)3 miktoarm stars. All copolymers were carefully characterized by size-exclusion chromatography (SEC), membrane osmometry (MO) and nuclear magnetic resonance (NMR) indicating a high degree of molecular and compositional homogeneity. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) were used to verify microphase separation and reveal the effect of the architecture on the adopted topologies. Through such a comprehensive characterization the authors have discovered that the high chain flexibility provided by the two polydiene segments affords promising properties previously unattainable from the corresponding triblock copolymers of these polydienes with polystyrene.

This work paves the way for further studies of material properties such as rheology and binary blends of the pure linear and non-linear copolymers with corresponding homopolymers (either hPB1,4 or hPI3,4).

We look forward to further exciting findings from the Avgeropoulos’ group.

Tips/comments directly from the authors:

  • Morphological characterization studies reveal the coherence of theoretical studies on the PS(PI1,4)n system and the experimental results of the PB1,4(PI3,4)n system (PS is substituted by PI3,4).
  • The only discrepancies from the relevant PS/PI system were found for two linear copolymers, where in both samples, hcp cylinders of the minority phase in the matrix of the majority were observed, instead of the expected DG cubic structure morphology.
  • The almost identical electron densities between the two polydienes led to impossible morphological characterization through small angle X-ray scattering (SAXS) and only transmission electron microscopy results verify the adopted morphology for each copolymer.
  • The adopted well-ordered nanostructures lead to the assumption that the segment–segment interaction parameter between the two polydienes of high 1,4-microstructure (∼92%) for the PB and ∼55–60% 3,4-microstructure for the PI is well above zero.
  • It was really exciting to verify that if the 3,4-microstructure for the PI blocks was not within the regime of ∼55–60% then a homogeneous structure was adopted (no microphase separation).
  • This regime of ∼55–60% 3,4-microstructure for the PI segments can be achieved by just adding a very small amount of a polar additive (∼1ml of THF) in the polymerization solvent ( 200 ml of benzene).

 

Citation to the paper: Synthesis, characterization and self-assembly of linear and miktoarm star copolymers of exclusively immiscible polydienes, Polym. Chem., 2021,12, 2712-2721, DOI: 10.1039/D1PY00258A

Link to the paper:

https://pubs.rsc.org/en/content/articlelanding/2021/py/d1py00258a#!divAbstract

 

Professor Athina AnastasakiDr. 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: Mechanically tough yet self-healing transparent conductive elastomers obtained using a synergic dual cross-linking strategy

Zhang et al. demonstrate a simple methodology for the synthesis of mechanically tough and self-healing materials.

Polymers that simultaneously exhibit high mechanical toughness and self-healing properties are essential to develop the next generation of materials for various applications including optoelectronics, sensors and healthcare devices. In this work, He, Li and co-workers developed a new route for the synthesis of a tough and self-healing supramolecular network by introducing Al(III)-carboxyl complexes into photo-polymerizable deep eutectic solvent. The resulting elastomers were mechanically tough and self-healing and demonstrated high transparency and stretchability as well as ionic conductivity. In particular, thanks to the synergic interaction of H-bonds and coordination bonds within the polymer matrix, over 80% self-healing efficiency for the damaged film could be obtained after 72 hours at ambient temperature. At the same time, the interaction between the fractures interfaces allows for the quick recovery of ion channels, therefore inducing electrical self-healing properties. The materials have been thoroughly characterized by a number of techniques including nuclear magnetic resonance, electrochemical impedance spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and tensile experiments. The developed methodology is simple, environmentally friendly and fast. The authors envision that their fundamental design concept will significantly contribute to the development of the next generation of tough and self-healing materials for potential use in flexible electronics and other applications.

Tips/comments directly from the authors:

  • Although in this paper we only report on the preparation of transparent conductive polymers from Al(III)-based polymerizable deep eutectic solvents (PDESs), this method can also be extended to other types of metal cations such as copper, zinc, cobalt and nickel ions. However, considering that some metal ions are coloured, the prepared conductive elastomers may be suitable for other areas of application.
  • During the experiments, we also found that PDES with trivalent iron ions could not be polymerized under UV light. The reasons for this phenomenon are not yet clear and we will continue to investigate.
  • The prepared transparent conductive elastomers are somewhat hygroscopic and therefore need to be kept dry during storage and use to maintain their performance stability.
  • If a high transparency film is desired, a release film should be necessary to insulate the polymer from oxygen during polymerization to maintain the homogeneity of the polymer structure.

Citation to the paper: Mechanically tough yet self-healing transparent conductive elastomers obtained using a synergic dual cross-linking strategy, Polym. Chem., 2021,12, 2016-2023, DOI:10.1039/D0PY01760D

Link to the paper:

https://pubs.rsc.org/en/content/articlepdf/2021/py/d0py01760d 

 

Professor Athina AnastasakiDr. 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: Synthesis of disulfide-bridging trehalose polymers for antibody and Fab conjugation using a bis-sulfone ATRP initiator

Forsythe and Maynard present a new strategy for the direct synthesis of disulphide-bridging trehalose polymers using a bis-sulfone ATRP initiator.

Conjugated polymers are often used to enhance the properties of therapeutic molecules such as antibodies and antigen binding fragments (Fabs). In this work, Forsythe and Maynard present a new strategy to prepare polymer-antibody/Fab conjugates by employing bis-sulfone end-groups installed via a functionalized atom transfer radical polymerization initiator. In particular, a bis-sulfone initiator was first synthesized and subsequently subjected to activators generated electron transfer (AGET) polymerization using ascorbic acid as the reducing agent. Upon optimizing the ligand concentration (special care was taken here as an excess of ligand causes a detrimental side reaction which results in broadening of the molecular weight distributions), disulphide-reactive trehalose polymers could be efficiently prepared with controlled molecular weight and fairly low dispersity, thus confirming a controlled polymerization. The polymers were then conjugated to a full Immunoglobulin G and its Fab fragment and the reaction proceeded quantitatively as confirmed by western blot and mass spectrometry. The stability of the resulting conjugates was then assessed by accelerated heat stress studies where the trehalose polymer was found to considerably increase the thermal stability of both Herceptin and Herceptin Fab. Importantly, this new strategy allows for a facile way to synthesize polymeric bioconjugates without the need for time consuming post-polymerization modification methods while also exhibiting very good monomer compatibility. As the authors conclude, they anticipate a continued exploration in the field of antibody and protein conjugation and we look forward to reading the next exciting findings from the Maynard group.

 

Tips/comments directly from the authors:

  • The bis-sulfone functionality is a robust system for the production of protein-polymer conjugates. However, due to its base-sensitivity, care needs to be taken when incorporating it into polymers. Since common ligands for AGET ATRP display reactivity towards the bis-sulfone, both reaction temperature and concentration should be kept low.
  • For performing conjugations using the bis-sulfone, we found it important to do a two-step reduction and alkylation where the reducing agent (DTT) was removed prior to the conjugation. To help avoid re-oxidation of the disulfides during this process, we used a buffer containing EDTA to prevent trace metal-mediated oxidation and additionally used desalting columns that allow for rapid removal of excess DTT.
  • While we demonstrate the applicability of the bis-sulfone initiator for AGET ATRP, the chemistry should be amenable to other controlled polymerizations such as RAFT. Incorporation into a chain transfer agent could further expand the diversity of chemistry available for antibody conjugation.
  • Trehalose polymers stabilized the antibody and Fab to temperature increases. However, the same polymer could also increase the stability of the conjugates in vivo since these polymers have improved the pharmacokinetics of other proteins.

Citation to the paper: Synthesis of disulfide-bridging trehalose polymers for antibody and Fab conjugation using a bis-sulfone ATRP initiator, Polym. Chem., 2021,12, 1217-1223, DOI: 10.1039/D0PY01579B

Link to the paper:

https://pubs.rsc.org/en/content/articlepdf/2021/py/d0py01579b 

 

Athina AnastasakiDr. 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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Discrete synthetic macromolecules: synthesis and applications – free webinar series

Flyer for discrete synthetic macromolecules webinar series. Online & free. dates 3, 10 and 17 MayPolymer Chemistry is very pleased to be sponsoring a new FREE webinar series on the topic of ‘Discrete synthetic macromolecules: synthesis and applications’ hosted by our very own Associate Editor, Filip Du Prez.

 

This webinar series, including Q&A opportunity, comprises three half day sessions featuring some absolutely top class speakers. The dates for your calendar are 3, 10 and 17 May!

 

Check out the full program and learn how to join here

 

3 May 10 May 17 May
·       Mike Meier ·       Laura Hartmann ·       Jean-François Lutz
·       Resat Aksakal ·       Mathieu Surin ·       Hans Börner
·       Alain Jones ·       Anja Palmans ·       Bruno De Geest
·       Ivan Huc ·       Elizabeth Elacqua ·       Christopher Alabi
·       Jeremiah Johnson ·       Ron Zuckermann ·       Craig Hawker

In addition, Polymer Chemistry will be making all papers in our related ongoing collection on ‘Molecularly defined polymers’ FREE to access for the month of May!

 

Check out our collection on Molecularly defined polymers here

 

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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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Paper of the month: Digital light processing 3D printing with thiol–acrylate vitrimers

Rossegger et al. present a new transesterification catalyst which can be applied in thiol-acrylate vitrimer systems enabling the fabrication of precise 3D objects.

image describing the work

Vitrimers are a unique class of materials that possess the remarkable property to be thermally processed in a liquid state while maintaining their network integrity. This property is induced owing to various thermo-activated exchange reactions including the catalyzed transesterification of hydroxyl ester moieties. However, the possibility to introduce dynamic covalent bonds into 3D printable photopolymers is challenging and the printed objects often suffer from a range of limitations such as low resolution, poor surface quality and lack of versatility. In addition, conventional transesterification catalysts exhibit poor solubility and present additional compromises on cure rate and pot life of photocurable resins. To this end, Schlögl and co-workers introduced a mono-functional oligomeric methacrylate phosphate as a new and efficient transesterification catalyst. The catalyst has many advantageous characteristics: it is liquid, easily dissolved in a range of acrylic monomers and can be covalently incorporated into the network across its methacrylate group. Once photo-cured, the dynamic thiol-click networks are able to rapidly undergo thermo-activated rearrangements of their network topology as shown by stress relaxation experiments. Importantly, when applied in thiol-acrylate vitrimer systems, precise 3D objects with 500 µm features using bottom-up digital light processing can be obtained. When compared to other commonly employed catalysts, the mono-functional methacrylate phosphate is superior both in terms of solubility and stress relaxation, thus unlocking a new toolbox of photocurable vitrimers.

 

Tips/comments directly from the authors:

  • Owing to their strong Brønsted acidity, organic phosphates are able to catalyze transesterifications in hydroxyl ester networks. They exhibit a better performance in catalyzing exchange reactions in dynamic photopolymers compared to Lewis acids such as Zn(OAc)2.
  • Stress relaxation kinetics increase with rising catalyst content. However, the catalyst content should not exceed 50 mol% as the resin formulation is getting destabilized. Below 50 mol%, the thiol-click resin is stable over several weeks. This is a clear advantage compared to conventional transesterification catalysts, which initiate thiol-Michael reactions and lead to a premature gelation of thiol-click resins.
  • Prior to the shape memory experiments it is important to thermally anneal the networks to form additional crosslink sites by hydrogen bonding, which lead to a change in thermal and mechanical properties. After 4 h at 180 °C, the network properties remain constant and the printed test specimen are able to repeatedly undergo shape changes after the programming step.
  • Organic phosphates are highly versatile transesterification catalysts and can be applied for imparting dynamic network properties in numerous photopolymer systems. Network architecture can be conveniently adjusted by the structure and functionality of the monomers and/or crosslinkers.

 

Citation to the paper: Digital light processing 3D printing with thiol–acrylate vitrimers, Polym. Chem., 2021,12, 639-644, DOI: 10.1039/D0PY01520B

Link to the paper:

https://pubs.rsc.org/en/content/articlepdf/2021/py/d0py01520b

 

Professor Athina AnastasakiDr. 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: Ring opening polymerization of ε-caprolactone through water

Atta et al. demonstrates a simplified ROP protocol which operates in the absence of any inert gas and without the need of drying any of the reaction’s reagents.

image describing the work

Ring Opening Polymerization (ROP) is arguably one of the most popular methodologies to synthesize biodegradable materials such as polycaprolactone (PCL) and poly (lactic acid) (PLA). However, a major drawback of this approach which severely limits its applicability is that it typically operates under completely moisture-free conditions, as water is well-known to deactivate the catalyst and terminate the propagating chains. To avoid water contamination, highly specialized equipment (e.g., Schlenk lines or glove boxes) as well as anhydrous reagents have to be employed which makes the process particularly tedious for both experts and non-experts. To overcome this, Gormley and co-workers have developed two elegant and simple methods that allow for the facile synthesis of PCL through ROP in a laboratory oven and without using any inert gas or dry reagents. In the first technique, a vacuum oven was employed to evaporate water from a traditional ROP reaction with stannous octoate as the catalyst while in the second approach titanium isopropoxide was utilized to simultaneously quench residual water and catalyze ROP. Impressively, and despite the simplicity of those methodologies, a range of chain lengths could be synthesized (degree of polymerization 25-500) with relatively good control over the molecular weight distributions of PCL (Đ < 1.5 for all cases). It is highlighted that a large excess of water impurities (750 ppm) could be tolerated by both methods yielding well-defined polymers at quantitative conversions. This work represents a great example of a simplified ROP which operates in the absence of complicated reactions set ups and can be performed in any laboratory. As the authors also remark, targeting even higher molecular weights or achieving even lower dispersity values will be the next challenge to address and we very much look forward to the next developments by the Gormley group.

Tips/comments directly from the authors:

  • The rational goal of this work is to enable the ROP reaction in an oven without inert gas environment and without drying or purifying the reagents.
  • The most exciting aspect of this work is to enable non-experts to synthesize custom polymers.
  • TTIP plays multiple roles in this ROP reaction. It not only initiates and catalyzes the polymerization reaction but also eliminates water from the reaction medium.
  • It is important for the audience that we should perform this experiment with minimal mixing time (within 1-5 sec) as water present in the air can contaminate CL.
  • The purity of CL can be easily checked by TTIP. A precipitate of TiO2 was formed when the water content of CL was above 750 ppm, and a cloudy solution was observed.

Citation to the paper: Ring opening polymerization of ε-caprolactone through water, Polym. Chem., 2021,12, 159-164, DOI: 10.1039/D0PY01481H

Link to the paper: https://pubs.rsc.org/en/content/articlepdf/2021/py/d0py01481h 

Professor Athina AnastasakiDr. 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: Mona Semsarilar

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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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