Archive for January, 2020

Paper of the month: Pulsed-addition ring-opening metathesis polymerization with functional enyne reagents

Zhang and Gutekunst utilize functional enyne molecules in pulsed-addition ring-opening metathesis polymerization to generate multiple functional polymer chains from a single 3rd generation Grubbs initiator.

Ring-opening metathesis polymerization (ROMP) has gained popularity within the polymer chemistry community thanks to the invention of functional group-tolerant ruthenium-based initiators. However, remaining challenges in the area include the use of stoichiometric amounts of metal and the difficulty to satisfactory control the end-group functionality. To address these challenges, Gutekunst and Zhang have elegantly employed functional enyne molecules in pulsed-addition ring-opening metathesis polymerization. This led to the generation of multiple functional polymer chains from a single 3rd generation Grubbs initiator. Importantly, all polymers synthesized displayed monomodal molecular weight distributions and very low dispersity values, as characterized by size exclusion chromatography, thus supporting the high efficiency of enyne chain-transfer. Detailed analysis of the molecular weights obtained from each pulse demonstrate that 50% of the ruthenium initiator remains active even after 10 cycles which corresponds to 4% of catalyst death per cycle. This is improved over previous established protocols where 8.5% of catalyst death per cycle was reported. The materials synthesized were further characterized by mass-spectrometry. In particular, matrix assisted laser desorption ionization showed extremely high end-group fidelity obtained using the enyne chemistry with a single polymer distribution and no observable side reactions. Different monomer structures were tested, the vast majority of which were compatible with the developed protocol. Bifunctional enyne molecules can also be used to give heterotelechelic polymers. Last but not least, the possibility of diblock copolymer formation was also examined yielding well-defined block copolymers with low final dispersity values. It is the author’s belief that their user-friendly and catalyst economical method will yield to the facile synthesis of materials with reduced metal contamination thus paving the way for further biomedical and electronic applications.

Tips/comments directly from the authors:

1. An inert atmosphere is important to this protocol, though a glovebox is not needed. All experiments were performed with a standard Schlenk line, and solutions were degassed by simply bubbling with nitrogen gas.
2. Three equivalents of the enyne CTA are used to ensure complete conversion of the Grubbs 3rd generation initiator, but only 1.2 eq is needed for full transfer after a given polymerization cycle of an exo-norbornene imide monomer. This reflects the differences in reactivity between ruthenium alkylidenes and benzylidenes with the enyne CTAs.
3. The exo-Oxanorbornene imide examined in this protocol was also effective but required 2.4 eq of the enyne CTA to recycle the system. This implies that different monomers may have variable reactivities. 1H NMR is very useful to monitor this process, as each of the ruthenium alkylidene/benzylidene species have diagnostic chemical shifts.
4. Small molecule byproducts are formed in each cycle but are inert under the reaction conditions and do not interfere with the polymerization.
5. If any readers are interested in using this approach, feel free to reach out to willgute@gatech.edu with any questions.

Citation to the paper: Pulsed-addition ring-opening metathesis polymerization with functional enyne reagents, Polym. Chem., 2020, 11, 259-264, DOI: 10.1039/c9py00965e

Link to the paper:
https://pubs.rsc.org/en/content/articlepdf/2020/py/c9py00965e

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Spotlight on Rongrong Hu: 2018 Polymer Chemistry Emerging Investigator

This week’s issue of Polymer Chemistry is our 2020 Emerging Investigators issue, which contains articles from polymer chemistry researchers in the early stages of their independent careers and is accompanied by an Editorial from Editor-in-Chief Professor Christopher Barner-Kowollik. To celebrate this issue we are delighted to feature the profile of Professor Rongrong Hu, who published in our 2018 Emerging Investigators issue. Below, Rongrong talks about her research journey, from student to Professor, and her feelings towards Polymer Chemistry!

“With my organic synthesis training as an undergraduate student at Peking University where I learned the great diversity of organic reactions, and the research experiences on luminescent polymer materials during my PhD study at The Hong Kong University of Science and Technology where I learned the fascinating functionalities that polymers could achieve, I tried to combine organic synthesis and polymer synthesis in my research after I started my career in 2014. We utilize efficient organic reactions for the development of new polymerization methodology and the exploration of new polymer structures and materials. After 5 years of research, I am fully convinced by the huge opportunity that comes with this interdisciplinary study.

Polymer Chemistry, with its topics highly focused on the synthesis, functionalities, and applications of polymers, always provides timely publication and best publishing experiences on exciting progress in the field. It can also sensitively catch new research trend and young polymer chemists. In the 2018 Emerging Investigator issue, we introduced our work about room temperature alkyne and sulfonyl azide-based multicomponent polymerizations, which represent efficient approaches for the convenient construction of polymers with unique structures and functionalities. Encouraged by the broad response of this paper, we further developed several elemental sulfur-based multicomponent polymerizations with practical implication. Most recently, I joined Polymer Chemistry as an Associate Editor, working with the top polymer chemists in the world, to look for most up-to-date innovative and exciting polymer chemistry.”

 

Read Rongrong’s 2018 Emerging Investigators series paper below!

Room temperature multicomponent polymerizations of alkynes, sulfonyl azides, and N-protected isatins toward oxindole-containing poly(N-acylsulfonamide)s
Liguo Xu,   Fan Zhou,   Min Liao,   Rongrong Hu*  and  Ben Zhong Tang*
Polym. Chem., 2018,9, 1674-1683

FREE to read and download until the 1st March 2020.

Biography

Rongrong Hu received her B.S. degree from Peking University and her PhD degree from Hong Kong University of Science and Technology. She is currently a Professor of the State Key Laboratory of Luminescent Materials and Devices at South China University of Technology.

She has published over 110 peer-reviewed articles and reviews. Her research interests include (1) the development of alkyne or isocyanide-based multicomponent polymerization methodology through the combination of organic and polymer synthesis, and (2) luminescent polymers with diverse structures and applications. Her current research focuses on the development of multicomponent polymerizations of elemental sulfur and sulfur-containing functional polymers.

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Spotlight on Antoine Buchard: 2018 Polymer Chemistry Emerging Investigator

This week’s issue of Polymer Chemistry is our 2020 Emerging Investigators issue, which contains articles from polymer chemistry researchers in the early stages of their independent careers and is accompanied by an Editorial from Editor-in-Chief Professor Christopher Barner-Kowollik. To celebrate this issue we are delighted to feature the profile of Dr Antoine Buchard, who published in our 2018 Emerging Investigators issue. Below, Antoine talks about his research journey and his feelings towards Polymer Chemistry!

Dr Antoine Buchard & Dr Ulrich Hintermair from The Centre for Sustainable Chemical Technologies were photogrpahed at a coffee meeting in The Edge for the University of Bath Alumni Relations Impact Report 2018. Shoot ref: 29456 Client: Rachel Skerry – Alumni Relations. Shoot Dates 8th and 9th November 2017

“I started my research career as a student working on new metal complexes for homogeneous catalysis, and only really ventured into polymer chemistry when some of our complexes showed interesting activities in the ring-opening polymerisation of lactide. Since then, I have been really interested in polymer chemistry because it is an incredibly diverse area, which I think offers a lot of creative space for both fundamental and applied work.

Today, using renewable feedstocks to make novel polymers is the underlying theme of my research program. I am particularly interested in using natural sugars as a sustainable, highly diverse and functionalisable resource to build polymers with interesting properties, including potentially less impact on the environment.  Our work addresses all aspects of the development of new polymers, from the synthesis of novel monomers, the design of new polymerisation catalysts and processes (including heterogeneous (ref Polym. Chem., 2019,10, 5894-5904)), detailed mechanistic and structure-properties studies, up to the applications of the polymers themselves. Polymer Chemistry is an ideal publication platform for this research, because of the broad scope of the journal, the diversity and expertise of the editorial team, as well as the breadth of article types possible.

Our group have for example recently discovered a method that replaces phosgene with carbon dioxide for the synthesis of cyclic carbonate monomers. We have successfully applied this protocol to various sugar derivatives, including deoxyribose (ref Polym. Chem., 2018,9, 1577-1582) and thymidine (ref Polym. Chem., 2017,8, 1714-1721) and developed promising tuneable, biocompatible and biodegradable polymers, which were also tested as tissue engineering scaffolds for regenerative medicine.

We took the opportunity of the 2018 Emerging Investigator issue to explore slightly different chemistry than usual and investigate the effect of changing some oxygen atoms with sulfur in the backbones of some of our sugar-based polycarbonate (ref Polym. Chem., 2018,9, 1577-1582). To this day it is still unclear! But along the way, we developed some new methodology for use of CS2 in the cyclothio-carbonation of the trans 1,3-diol motif of ribofuranoses, and isolated the first examples of cyclic xanthate monomers derived from natural sugars. Using controlled ring-opening polymerisation, regular poly(xanthate) and alternating poly(trithio-alt-thiocarbonate) species were obtained, and we showed that the sugar backbone influenced greatly the regioselectivity of monomer opening. These polymers formed a new family of degradable sulfur-containing sustainable polymers that attracted some attention from material scientists, and that we are still investigating today and hoping to report on further soon. Featuring in the 2018 Emerging Investigator issue was a great recognition and reward for the work done in my group over the past few years, and has spurred us to keep working in this area.

I am really looking forward to the 2020 Emerging Investigator issue of Polymer Chemistry. I am always curious to discover newcomers in the field and how they envisage the field. With the biennial Pioneering Investigators issue, these issues really set themselves apart from regular issues. I have found that authors usually want to rise to the challenge and report especially exciting results, so it is often a great read!”

 

Read Antoine’s Polymer Chemistry papers below!

Polymer-supported metal catalysts for the heterogeneous polymerisation of lactones
Ioli C. Howard, Ceri Hammond and Antoine Buchard
Polym. Chem., 2019,10, 5894-5904

Polymers from sugars and CS2: synthesis and ring-opening polymerisation of sulfur-containing monomers derived from 2-deoxy-D-ribose and D-xylose
Eva M. López-Vidal, Georgina L. Gregory, Gabriele Kociok-Köhn and Antoine Buchard
Polym. Chem., 2018,9, 1577-1582 (Emerging Investigator 2018 Issue)

CO2-Driven stereochemical inversion of sugars to create thymidine-based polycarbonates by ring-opening polymerisation
Georgina L. Gregory, Elizabeth M. Hierons, Gabriele Kociok-Köhn, Ram I. Sharma and Antoine Buchard
Polym. Chem., 2017,8, 1714-1721

Polymers from sugars and CO2: ring-opening polymerisation and copolymerisation of cyclic carbonates derived from 2-deoxy-D-ribose
Georgina L. Gregory, Gabriele Kociok-Köhn and Antoine Buchard
Polym. Chem., 2017,8, 2093-2104

 

Biography

Antoine is a Royal Society University Research Fellow and Reader in Chemistry within the Centre for Sustainable and Circular Technologies (CSCT) at the University of Bath (UK). His research interests include novel chemical transformations and use in catalysis of renewable resources for the synthesis of sustainable polymers and their applications. He is also a member of the UK Catalysis Hub.

Antoine studied at the École Polytechnique in France, obtaining the École Polytechnique’s Diploma and a Master’s degree in chemistry in 2006. He also completed his PhD at the Ecole Polytechnique in 2009, under the supervision of Prof Pascal Le Floch. Antoine was then a Postdoctoral Research Assistant at Imperial College with Prof Charlotte Williams. He worked Air Liquide R&D before returning to academia in 2013, as a Whorrod Research Fellow within the CSCT at the University of Bath.

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Polymer Chemistry Author of the Month: Claude St Thomas

Claude St ThomasClaude St Thomas studied chemistry at the École Normale Supérieure, Université d’État d’Haïti, Port au Prince, Haïti. In 2008, he moved to Mexico where he obtained MSc and PhD degrees in polymer chemistry at the Centro de Investigación en Química Aplicada (CIQA) under the guidance of Dr. Ramiro Guerrero Santos. During his PhD studies, he undertook two research stays at the Laboratory of Chemistry and Processes of Polymerization (LCPP), in Lyon, France under the supervision of Prof Bernadette Charleux and Dr. Franck D’Agosto. He designed a novel dual RAFT/NMP chain transfer agent for a tandem polymerization and investigated its use for preparing the self-assembled nanoparticles. This investigation was awarded with the 2015 Rafael Illescas Frisbie prize from the Mexican Chemistry Society as the best PhD thesis. In the same year, he was promoted as a CONACYT research fellow at CIQA.

His research mainly focuses on the preparation of well-defined multiblock copolymers and the development of novel associative polymers featuring stimuli-responsive groups using reversible deactivation radical polymerization (RDRP) techniques. He is also interested in the rheological properties of polymers for applications in coatings, paints, enhanced oil recovery, and water treatment.

What was your inspiration in becoming a polymer chemist?

In my childhood, I was always fascinated by nature. At the beginning, I dreamed about becoming an agronomist. However, my interest for chemistry started in high school by the teachings from chemistry lecturer Sylvain Jean Desir. There, I understood that chemistry is the basis of life. During my MSc and PhD studies I worked with materials of common and daily use and a special interest for polymer chemistry started rising.

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

In our research group, scientific contributions related to the preparation of water-soluble copolymers have been previously published under the supervision of Dr. Enrique Javier Jiménez Regalado using free radical polymerization. In 2014, the “Consejo Nacional de Ciencía y Tecnología” (CONACYT, México) started a new program for addressing solutions to national problems, where young researchers were engaged and assigned to specific projects. Since, I started in my current position in 2015 and inspired by the versatility of the RAFT polymerization technique, my current research work focuses on the development of novel pathways for preparing well-defined water-soluble associative copolymers.

Inspired by the RDRP techniques and their feasibility for synthesizing polymeric materials with unprecedented properties, our recent contribution describes a new strategy for preparing environmentally-friendly water-soluble associative copolymers using the RAFT technique.

Which polymer scientist are you most inspired by?

A group of scientists have impacted my career. I appreciate the discipline, rigor and professional achievements of both Prof Bernadette Charleux and Dr. Franck D’Agosto. Fascinated by RDRP techniques, I am also inspired by three experts in RDRP: Prof Craig J. Hawker, Prof. San H. Thang and Prof. Krzysztof Matyjaszewski. Their publications describing processes for synthesizing polymers with specific characteristics might allow the use of these materials in different industrial applications.

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

Based on application areas of polymeric materials, it would be difficult to mention researchers who will have a big impact on the field. Notwithstanding, I select Dr. Francesco Picchioni (University of Groningen). His research on the development of chemical materials for application in Enhanced Oil Recovery (EOR) displays great interest and could impact the field. For these researches, I am also impressed by the research works of Dr. Michael F. Cunningham (Queens University) and Sébastien Perrier (University of Warwick)

How do you spend your spare time?

Outside of professional activities, I enjoy spending time with my family (wife and four year-old daughter-Nicole) and visiting natural places. My favorite sport is soccer, so I enjoy playing it with friends. I also enjoy playing guitar and reading about new scientific developments and culture.

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

Probably an agronomist due to my passion for natural sciences, because it was my first dream.

Read Claude’s full article now for FREE until the 31st January!


Preparation of hydrophobically modified associating multiblock copolymers via a one-pot aqueous RAFT polymerization

Graphical abstract: Preparation of hydrophobically modified associating multiblock copolymers via a one-pot aqueous RAFT polymerization

We describe an efficient strategy for the preparation of hydrophobically associating multiblock copolymers using the RAFT technique. Polymerization reactions were carried out by a one-pot aqueous RAFT polymerization at 70 °C using a symmetrical trithiocarbonate as a chain transfer agent (CTA) in aqueous media. The macroRAFT polyacrylamide (PAM) was synthetized and chain extended by polymerization of N,N′-dihexylacrylamide (DHAM) and acrylamide (AM), respectively. The resultant polymers were intensely characterized by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) spectroscopy, diffusion-ordered spectroscopy (DOSY), Fourier transform-infrared (FT-IR) spectroscopy and rheology. The structure and insertion of a hydrophobic block (PDHAM) into the backbone were carefully demonstrated. The rheological measurements confirmed the effect of the hydrophobic block number on the viscosity of polymers at different concentrations and the formation of a reversible physical network of entangled polymers in aqueous media. Moreover, the incorporation of the hydrophobic block (PDHAM) was established by the oscillatory measurement.


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. 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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