Archive for June, 2021

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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