Archive for the ‘Uncategorized’ Category

Keary Engle and Thomas Bennett: Winners of the ChemComm Emerging Investigator Lectureship 2021!

Keary and Thomas join recent past winners Raffaella Buonsanti (2019), Corinna Schindler (2019), and Bill Morandi (2020). Learn more about Keary and Thomas below.

Image of Keary Engle

Keary Engle received his PhD in chemistry from Scripps Research and his DPhil in biochemistry from Oxford University in the unique, five-year Skaggs-Oxford Scholarship program that he completed in 2013. Within the program, he trained with renowned chemists Jin-Quan Yu at Scripps Research and Véronique Gouverneur and John M. Brown at Oxford. Among his many honours, Keary has been awarded a 2019 Camille Dreyfus Teacher-Scholar Award, the 2019 Novartis Early Career Award in Chemistry, a 2020 Cottrell Scholar Award, a 2020 Eli Lilly Organic Chemistry Award, the 2020 Amgen Young Investigator Award, and most recently, a 2021 NSF CAREER Award.

He is currently a Professor in the Department of Chemistry at Scripps Research. His group harnesses the power of catalysis to advance the efficiency, effectiveness and sustainability of chemical synthesis. You can learn more about Keary’s group and his research on Twitter @englelab.

Learn more about Keary’s research by reading his recent Feature Article in ChemComm:

Recent advances in palladium-catalyzed (hetero)annulation of C=C bonds with ambiphilic organo(pseudo)halides

Keary M. Engle et al.

Chem. Commun., 2021, 57, 7610-7624

This article will be free to read from 1st December 2021 – 1st January 2022.

 

Thomas Bennett

Tom was awarded his PhD in 2012 at the University of Cambridge, where he worked with Professor Anthony Cheetham FRS on the physical properties of hybrid frameworks. He has received several fellowships and awards, including a Royal Society Research Fellowship (2016), the Woldemar A. Weyl award for glass science (2019), the Philip Leverhulme Prize in Chemistry (2019) and the Royal Society of Chemistry Harrison Meldola Memorial Prize (2020). He has held visiting positions at the University of Kyoto, the Wuhan University of Technology, and the University of Canterbury New Zealand | Te Whare Wānanga o Waitaha, and is vice-chair of the international MOF advisory committee, and outgoing chair of the Royal Society of Chemistry Porous Materials Group.

He is currently an Assistant Professor at the University of Cambridge, where his research group are best known for the discovery of hybrid melt-quenched glasses, and seminal works exploring the interface of the coordination polymer, MOF and glass domains. Find out more about Tom and his group on Twitter @thomasdbennett.

Learn more about Thomas’ research by reading his recent Open Access Communication in ChemComm:

Glassy behaviour of mechanically amorphised ZIF-62 isomorphs

Thomas D. Bennett et al.

Chem. Commun., 2021, 57, 9272-9275            

As part of the Lectureship award, Keary and Thomas will each be presenting lectures over the coming 12 months. Details of the lectures will be announced in due course but keep an eye on Twitter @ChemCommun for details!

Keep up-to-date with our latest journal news on Twitter @ChemCommun or via our blog! Learn more about ChemComm online!

Sign up for a Chemistry Briefing: if you would like to stay informed about new resources and publishing updates, please opt in to our email newsletter.

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ChemComm Milestones – Dong-Dong Zhou

Congratulations to Dong-Dong Zhou for publishing his first independent research article in ChemComm. Be sure to read Dong-Dong’s #ChemComm1st article ‘Single-crystal superprotonic conductivity in an interpenetrated hydrogen-bonded quadruplex framework‘ in our collection, ChemComm Milestones – First Independent Articles.

Find out about his experience as a first-time author in our recent interview.

 

 

 

What are the main areas of research in your lab and what motivated you to take this direction?

The design and syntheses of new crystalline porous materials, such as porous coordination polymers (PCPs) or metal–organic frameworks (MOFs), and we pay more attention to the influence of their dynamic behaviours on their properties of adsorptive separation, catalysis, conduction and so on. MOF materials possess the advantages of designable and modifiable structures, more importantly, the structure-activity relationship between their structures and properties can be revealed at the atomic or molecular level, which is helpful to guide the design new materials with specific performance. Moreover, MOF materials are expected to have unique properties that traditional materials cannot, such as the “intermediate-sized molecular sieves” we reported earlier in Nat. Mater.

Can you set this article in a wider context?

New crystalline porous materials based on supramolecular interactions such as coordination bonds and/or hydrogen bonds show good prospects in many application fields. However, this kind of materials is easy to dynamically change under external stimuli, which may help us to discover some new things/mechanisms, or to further understand some certain processes in nature. For example, proton dynamic behaviour’s in fuel cells and beings are closely related with their performances and life processes. In this work, we designed and synthesized a porous hydrogen-boned quadruplex framework (like G-quadruplex in the chromosome), in which there exists one-dimensional spiral water chains in the channels. We prepared their large-size single crystals and measured the anisotropic proton conductivity, which demonstrated that it showed a super protonic conductivity along the water chains. Computation simulations showed that the protons of water transfer between oxygen atoms accompanied with water molecules moving, that is proton vehicle mechanism.

What do you hope your lab can achieve in the coming year?

I hope that students in the our lab will discover “the beauty of crystals”, “the secret of dynamics” and “the rigor of science”, and quickly grow into the relevant researchers with independent thinking and judgment through scientific research training in the next year, so that they can start their own favourite and skilled scientific research fields in one day.

Describe your journey to becoming an independent researcher

During my undergraduate period, I joined Prof. Chunlin Ni group in South China Agricultural University, where I deeply felt in the power of single crystal X-ray diffraction technology and began to study the growth of single crystals. In 2011, I went to Sun Yat-Sen University for further study, and mainly carried out the researches on the design and synthesis of crystalline porous materials under the guidance of Prof. Jie-Peng Zhang, and obtained my Ph.D. degree in 2016. Then as an associate researcher, I assisted to guide graduate students and Ph.D. candidates to carry out their researches on porous materials for adsorptive separation and catalysis in the group of Prof. Xiao-Ming Chen and Jie-Peng Zhang. In 2019, I became an associate professor in Sun Yat-sen University, and began to independently guide graduate students to carry out scientific research. My research interests mainly focus on the dynamic behaviours of crystalline porous materials playing roles in the related properties.

What is the best piece of advice you have ever been given?

Maybe it is from the Zhouyi “天行健,君子以自强不息;地势坤,君子以厚德载物”, which means “As heaven maintains vigor through movements, a gentle man should constantly strive for self-perfection. As earth’s condition is receptive devotion, a gentle man should hold the outer world with broad mind”.

Why did you choose to publish in ChemComm?

Coincidentally, my first academic paper was also published in ChemComm as outside front cover, and all three papers during my Ph.D. candidate stage were published in ChemComm, which caused I was teased as “the king of ChemComm” by my friends at that time. Actually, as a chemistry researcher, we all know ChemComm is a very good chemistry journal for quick reporting of significant results with scientific value. And I’ve been focus on the papers published on ChemComm, in which a lot of good ideas also inspires me. In the future, I also hope we have more opportunities to publish my works in ChemComm.

 

Dr. Dong-Dong Zhou was born in China in June 1990. He received his B.Sc. degree (2011) from South China Agricultural University, and his Ph.D. degree (2016) in inorganic chemistry under the supervision of Professor Jie-Peng Zhang from Sun Yat-Sen University. Then, he became an associate researcher in Xiao-Ming Chen Group at Sun Yat-Sen University. Since 2019, he has been an associate professor in School of Chemistry at Sun Yat-Sen University. His current research interest focuses on the design and syntheses of porous coordination polymers or metal–organic frameworks, especially for their dynamic structural changes playing a role in the applications of adsorptive separation, catalysis, proton conduction etc.

 

 

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ChemComm Milestones – Thanthapatra (Valentine) Bunchuay

Exciting news – Thanthapatra (Valentine) Bunchuay recently published his #ChemComm1st article:
Pertosylated pillar[5]arene: self-template assisted synthesis and supramolecular polymer formation. We wanted to find out about Thanthapatra’s experiences reaching a ChemComm Milestone. Find out more in our interview below.

Read about Thanthapatra and the SupraValentine group here:

What are the main areas of research in your lab and what motivated you to take this direction?
Our research in the ‘SupraValentine’ Lab at Mahidol University focuses on supramolecular and macrocyclic chemistry, which covers a broad area of interests. Learning from molecular recognition processes in nature, our lab has employed various forms of intermolecular non-covalent interactions as tools to construct supramolecular architectures. Our prime interest is the synthesis of novel macrocyclic host molecules decorated with specific functional groups to facilitate binding or encapsulation of target guest species including cations, anions, ion-pairs, and neutral molecules. These systems have been designed to self-assemble into complex nanostructures for tailored applications such as; stimuli responsive materials, smart sensors, and recovery and extraction agents. The most effective and elegant supramolecular chemistry is performed by nature and so taking inspiration from biological systems, complemented by one’s own imagination are key to my research in supramolecular chemistry. I am motivated by the idea of inspiring others to actively contribute to the exciting field of supramolecular chemistry, which is still a relatively small society in Thailand.

Can you set this article in a wider context?
Pillar[5]arenes are a class of macrocycles having a five-fold symmetric structure constructed from electron-rich aromatic surfaces. These macrocycles can encapsulate a range of guest molecules and especially electron deficient linear alkyl moieties. Usually, these are obtained by Lewis acid catalyzed macrocyclization reactions of dialkoxy benzene monomers. However, to date the synthesis of highly decorated Pillar[5]arenes has been hindered by low yields and/or tedious synthesis. In this work, we incorporated tosylate functional groups into the monomeric unit to synthesize a pertosylated pillar[5]arene structure. The discovery of a serendipitous self-templation effect facilitated the high yielding synthesis (70%) of a perfunctionalised pillar[5]arene derivative, in contrast to the previous paradigm for decafunctionalised pillararenes of this kind. The presence of ten tosylate units not only facilitates the formation of a supramolecular polymer and nanofiber in both the solid-state and solution phase, through concerted weak hydrogen bond formation, but serves as an excellent synthetic handle in the rapid construction of highly derivatisable and multivalent nano-scafffolds. We believe that these results provide great promise for the versatility of subtle, yet powerful, unorthodox non-covalent interactions in the synthesis and functionality of supramolecular systems. Considering the rich host-guest chemistry of pillararenes we hope that our contribution to the rapid and facile access of diversifiable platforms will help further propel the inherent ‘stardom’ of pillararene based materials.

What do you hope your lab can achieve in the coming year?
My lab has been set up since August 2019. Thanks to the unfailing kindness and generosity of my previous M.Sc. supervisor, Assoc. Prof. Jonggol Tantirungrotechai I have been able to kick-start my research career. Jonggol’s sharing of space and facilities were crucial to my first independent publication. In this coming year, we hope that we will discover many secrets of nature through our systems and aim to communicate our work to the chemist community (publish more articles!). Again, thanks my students and my great colleagues especially, Prof. David Harding for your effort.

Describe your journey to becoming an independent researcher.
It’s been a long journey I would say. Since grade 10 in high school, I have received a Development and Promotion of Science and Technology Talent Project (DPST) scholarship from the Thai government to study any ‘pure science’ until Ph.D. and without hesitation chose a chemistry major. I received my B.Sc. (2011) and M.Sc.(2014) from the Faculty of Science in Mahidol University, Thailand. During that time, I was allowed to explore a broad range of chemistry from iodine mediated synthetic methodology to the post-functionalisation of MOFs for catalysis. In 2014, I had a great opportunity to join the research group of Prof. Paul D. Beer at the University of Oxford. During this time, it is no exaggeration to say my life was totally changed. It was truly an honour to be under the supervision of Paul leading with uninhibited imagination, enthusiasm and encouragement, undoubtedly influencing how I pursue science in my own research group. Apart from synthetic chemistry skills, I also learnt to be patient and deal with the dynamics of a large research group. In particular, recalling the valuable discussions with Paul and other group members helping to stimulate my own research interests. Sometimes my ideas were useful and of course some were useless, but all were useful learning experiences nonetheless. In January 2019, I secured the position of inorganic lecturer at Department of Chemistry, Faculty of Science, Mahidol University, Thailand. Starting my own research group in August 2019 with one graduate student and two undergraduate students, 10 months later we were lucky enough to publish our first work in ChemComm.

What is the best piece of advice you have ever been given?
During my time as a D.Phil student, it was certainly the most transformative and important journey of my life. I started in the Beer group with little synthetic organic experience, so my first year was a steep (but fun) learning curve. Sometimes we succeeded, many times we failed. As Paul always says “Learn to walk before you can run”, you have to keep learning, doing chemistry, and developing yourself gradually. The day that you are strong enough, you can run and jump into whatever areas that you are not familiar with. Another invaluable piece of advice from him that I really like is “Good work can be published everywhere”, however he said this when our first paper together was rejected!

Why did you choose to publish in ChemComm?
ChemComm consistently publishes many excellent works. The journal’s universally respected reputation presented the best platform to initiate my independent scientific career. The clear paper format and straightforward submission processes were also important in my decision to submit our very first publication from the ‘SupraValentine Lab’. Many thanks to the Royal Society of Chemistry (RSC) and ChemComm again for this great opportunity to support early career researchers from wherever they are in the world. This experience has encouraged me and I hope it will inspire others to continue producing good science.

Thanthapatra (Valentine) Bunchuay, a recipient of the Royal Thai Scholarship (2004 – 2018), graduated from Mahidol University (Thailand) with a first class honour B.Sc. degree in 2011. After that, he carried on the research with Associate Professor Jonggol Tantirungrotechai in the functionalisation of metal-organic frameworks (MOFs) for heterogeneous catalysis applications, graduating with an M.Sc. degree in chemistry in 2014. In the same year, he moved to the United Kingdom to join the group of Professor Paul Beer at the University of Oxford, where he developed sigma-hole donor host molecules for anion and ion-pair recognition in aqueous media. Having finished his D.Phil. degree in 2018, he is now working as an inorganic chemistry lecturer at Mahidol University where he has started The SupraValentine Research Lab. His research focuses on applications of supramolecular host-guest chemistry in functional materials and nanostructures.

Our collection of #ChemComm1st articles, including Thanthapatra’s, are available here. Don’t forget to follow us on Twitter for the latest #ChemCommMilestones news.

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Finding early warnings in chemical systems

Our world runs on systems of ever-increasing complexity, be they natural or human created. Their behavior can generally be modeled and operates within a normal range… until it hits a tipping point at a border between two behavioral regimes. Once that threshold is reached the system acts in dramatically different, and often destructive, ways. However, there are often warning signs right around the tipping point that can serve to alert careful observers that the danger zone is near. By finding ways to identify and monitor this behavior either contingency plans can be put in place or the problem corrected before it becomes catastrophic. While much of this has been studied for large systems like the stock market or ecosystems, researchers recently applied this to chemical systems.

The utility of identifying early warning signals isn’t limited to preventing massive changes; it can also help bound regions of different functionality in chemical systems. To explore this, researchers used a trypsin oscillator system they previously developed that has two modes of flow (Figure 1), either sustained oscillations in trypsin concentration or dampened oscillations that eventually lead to a steady concentration of trypsin. By changing flow rate, temperature, or reagent concentration the researchers could tune the behavior of the system to test either active or passive monitoring schemes to find early warning signs. Since they knew what conditions produced each mode, they could operate the system right at the boundary and watch its behavior.

Figure 1. Schematic of trypsin system with examples of oscillation patterns.

In the “active” experiments the researchers intervened in the system’s normal functioning and watched how its response, the “critical slow down phenomena,” changed as the conditions were brought closer to the boundary. In “passive” experiments, the researchers simply brought the system close to the boundary and monitored the shape of the oscillation waves focusing on their full-width half maxima (FWHM). In the series of active sensing experiments, the researchers waited to see how long it took the system to re-establish sustained oscillations after a change in temperature. They expected to see this recovery time increase as the system was brought closer to the edge, aka the “critical slow down phenomena.” In their experiment they elevated the temperature of the system to 49.0 oC and observed how long it took to recover to either 24.3 oC (well within the sustained regime) or 20.9 oC (near the behavioral boundary). They saw the expected dramatic increase in time to return to sustained oscillation, with the system recovering in 10.7 hrs at 24.3 oC, but taking three times as long, 32.8 hrs, when the final temperature was 20.9 oC (Figure 2). The experimental results were further validated by theoretical modeling, where experimentally challenging positions at the very edge of the boundary could be explored and showed the same general behavior.

Figure 2. Top: active monitoring experiments at two different temperatures showing the differences in time needed to recover sustained oscillations. Bottom: comparison of modeled and experimental recovery times.

The theoretical modeling was further used to create a map of passive monitoring space, looking at the variations in FWHM. They saw that as the system moves away from the center of the oscillation regime the FWHM increases as the peaks broaden. This becomes more pronounced as the conditions approach the behavioral boundary. This provides a baseline knowledge with multiple types of measurements to compare the stability of the simple system over a range of conditions. Additionally, this system and others like it can serve as the base for modeling more complex systems of which they are a part.

To find out more, please read:

Early warning signals in chemical reaction networks

Chem. Commun., 2020, Advance Article

Oliver R. Maguire, Albert S. Y. Wong, Jan Harm Westerdiep and Wilhelm T. S. Huck

About the blogger:

Dr. Beth Mundy recently received her PhD in chemistry from the Cossairt lab at the University of Washington in Seattle, Washington. Her research focused on developing new and better ways to synthesize nanomaterials for energy applications. She is often spotted knitting in seminars or with her nose in a good book. You can find her on Twitter at @BethMundySci.

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The Cram Lehn Pedersen Prize in Supramolecular Chemistry


 

The International Committee of the International Symposium on Macrocyclic and Supramolecular Chemistry is pleased to invite nominations for the Cram Lehn Pedersen Prize for young supramolecular chemists.

The Cram Lehn Pedersen Prize, named in honor of the winners of the 1987 Nobel Prize in Chemistry, will recognise significant original and independent work in supramolecular chemistry.

Those who were awarded their PhD on or after 1st January 2009 (or who have an award of PhD date together with allowable career interruptions* that would be commensurate with award of their PhD on or after 1st January 2009) are eligible for the 2020 award. The winner will receive a prize of £2000 and free registration for the ISMSC meeting in Sydney, Australia. In addition to giving a lecture at ISMSC, a short lecture tour will be organized after the meeting in consultation with the Editor of Chemical Communications, the sponsor of the award.

Nomination Details

You may nominate yourself, but a nomination letter is recommended. Nomination materials should include: CV, list of publications (divided into publications from your PhD and post-doc, and those from your independent work), and be sent to Prof. Roger Harrison (ISMSC Secretary) at roger_harrison@byu.edu by 31st December 2019.

*Allowable career interruptions include primary caregiver’s responsibilities, illness, disability or parental leave and must be outlined in a cover letter with supporting documentation. See  https://www.chem.byu.edu/faculty-and-staff/resources/international-symposium-on-macrocyclic-and-supramolecular-chemistry/awards/ for specific details.

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Chemical Communications: Editor’s Choice

Be sure to read our latest Editor’s Choice article as chosen by Associate Editor Jean-Louis Reymond!

This article is free-to-access until 8th November and can be found alongside our previously chosen articles in our online Editor’s Choice web-collection!

Heptylmannose-functionalized cellulose for the binding and specific detection of pathogenic E. coli” by Jean-Louis Reymond:

In their communication “Heptylmannose-functionalized cellulose for the binding and specific detection of pathogenic E. coli” Madeleine Cauwel et al. exploited the well-known FimH lectin system to devise a selective detection system for adherent-invasive E. coli (AIEC) involved in the pathogenesis of Crohn’s disease (CD). FimH is well known to bind mannosyl glycosides and to occur in AIEC. The trick here was to prepare a modified cellulose (as nanofiber or paper) using click chemistry, profile its lectin binding with state-of-the art chip analysis, verify its ability to block binding of AIEC from a CD patient to intestinal epithelial cells and to decrease AIEC levels in gut microbiota in a murine model, and finally to show that the modified paper binds selectively to pathogenic AIEC but not to benign E. coli.

Simple but effective chemistry, thorough experiments with relevant samples, impressive results. Chemical biology at its best.

 

 

Find our full Editor’s Choice collection online!

Keep up-to-date with our latest journal news on Twitter @ChemCommun or via our blog!

Learn more about ChemComm online! Submit your latest high impact research here!

 

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Chemical Communications: Editor’s Choice

Be sure to read our Editor’s Choice articles as chosen by Associate Editors Prof. Penny Brothers & Prof. Manfred Scheer!

Both articles are free-to-access until 4th October and can be found alongside our previously chosen articles in our online Editor’s Choice web-collection!

 

NO sorption, in-crystal nitrite and nitrate production with arylamine oxidation in gas–solid single crystal to single crystal reactions” by et al., as chosen by Penny Brothers:

This year marks 100 years since Alfred Werner’s death in 1919, and it is over a century since he won the 2013 Nobel prize for developing the conceptual framework that we now understand as coordination chemistry. Studies on cobalt complexes formed the cornerstone of Werner’s work, and this paper shows they are still relevant and important well into the 21st century, although with some surprising twists.  Single crystals of tetranuclear Co(II) and Co(III) complexes chemisorb nitric oxide (NO) which, after exposure to O2 physisorbed from air, is transformed to nitrite, nitrate and an aryl nitro group in remarkable single crystal to single crystal reactions.  The medical and biological significance of NO and the solventless redox chemistry all occurring in the crystalline phase suggest exciting possibilities for its highly selective capture and conversion.

 

 

Imidazolium-benzimidazolates as convenient sources of donor-functionalised normal and abnormal N-heterocyclic carbenes” by et al., as chosen by Manfred Scheer:

Mesomeric betaines are related to N-heterocyclic carbenes because of their interconversion by tautomerisation and therefore can act as “instant carbenes”. The authors established now imidazolium-benzimidazolates as a new and highly versatile “instant carbene” system. Depending on the steric demand of the imidazole N-substituent, normal but also abnormal NHC carbene coordination is observed. Thus, unstable but nevertheless highly interesting species are available starting from stable betainic precursors. Therefore, this paper contributes substantially to the chemistry of normal and abnormal N-heterocyclic carbenes.

 

 

 

Find our full Editor’s Choice collection online!

Keep up-to-date with our latest journal news on Twitter @ChemCommun or via our blog!

Learn more about ChemComm online! Submit your latest high impact research here!

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Mechanical Stress Turns These Dendrimers Blue

We all know what happens when materials take too much mechanical stress – they eventually break.

What if you could easily tell when something like a support was close to its maximum stress, before it undergoes a catastrophic event, just by looking at it? One option is to incorporate a mechanochromic polymer, a polymer that changes color when under sufficient mechanical stress, to provide a visual indicator that a material has reached a specific stress threshold. The polymers don’t need to be entirely composed of mechanochromically active moieties to exhibit useful properties; many studies have focused on a single active mechanophore at the center of a large polymer chain. In fact, the mechanical force is greatest at the center of a chain and is directly proportional to the length of the chains. This holds for polymers in solution but hasn’t been extensively studied in the types of bulk systems useful for applications.

Recently, researchers in Japan set out to characterize the effects of chain length and branching on mechanochromic dendrimers, polymers with monodisperse and regularly branched globular structures. Showing that dendrimers exhibit mechanochromism is already a novel result, but their well-defined nature allowed the researchers to draw correlations between structure and bulk responsiveness. They employed diarylbibenzylfuranone (DABBF) as the mechanochromic moiety since it generates arylbenzofuranone (ABF) radicals, which are blue, air-stable, and electron paramagnetic resonance spectroscopy (EPR) active, when exposed to mechanical force (Figure 1).

Figure 1. Structure of the DABBF moiety and the active ABF radicals generated by its dissociation.

These characteristics allow for straightforward qualitative and quantitative analysis. The team coupled the DABBF moiety with two series of dendrimers, with increasing generations having larger and more highly branched monomer units, to create a range of molecular weights and degrees of branching for study. The dendrimers showed a color change from white to blue (Figure 2) when ground in a ball mill, which was used to ensure the reproducibility of the force applied to all samples.

Figure 2. Photographs of the first (top) and second (bottom) mechanochromic dendrimers before and after grinding, showing the color change associated with the generation of ABF radicals.

EPR measurements confirmed the presence of the ABF radicals in the samples after milling, demonstrating that the color change is due to the cleavage of the DABBF. The integrated EPR spectra were used to quantitatively determine the percentage of DABBF moieties that dissociated. The responsiveness of the dendrimers increased exponentially with increasing generation and branching. However, the primary factor governing ABF generation was found to be molecular weight. Two dendrimers with different levels of chain entanglement, but similar molecular weights, exhibited comparable cleavage ratios.  The question then became does molecular weight increase the transfer efficiency of force to the DABBF or does the increased steric bulk make it harder for the ABF radicals to recombine? To probe the kinetics of this process, the researchers varied the grinding time and saw that within 5 minutes all the highly branched samples reached their maximum dissociation level. Additionally, monitoring the ABF recombination showed that even after 6 hours approximately 95% of the radicals remained dissociated in all 3rd and 4th generation dendrimers. These data suggest that the enhancement in responsiveness can be attributed to better force transmission to the DABBF.

This work shows mechanoresponsiveness in a range of dendrimers with varying degrees of branching and rigidity. Not only did they demonstrate novel activity, but the researchers also probed the mechanism of the enhanced activity with increasing molecular weight. This initial study opens avenues to explore polymer rigidity, surface functionality, and other dendrimer features to design new, functional materials.

To find out more, please read:

Mechanochromic dendrimers: the relationship between primary structure and mechanochromic properties in the bulk

Takuma Watabe, Kuniaki Ishizuki, Daisuke Aoki, and Hideyuki Otsuka

Chem. Commun., 2019, 55, 6831-6834.

About the blogger:

Beth Mundy is a PhD candidate in chemistry in the Cossairt lab at the University of Washington in Seattle, Washington. Her research focuses on developing new and better ways to synthesize nanomaterials for energy applications. She is often spotted knitting in seminars or with her nose in a good book. You can find her on Twitter at @BethMundySci.

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Synthesizing Polymers Using CO2

Ring-opening polymerizations produce commercial polymeric materials including epoxy resins, but they usually liberate small molecules such as the greenhouse gas, CO2. In the context of climate change, it is urgent to reduce CO2 emissions. Recently, a group of UK researchers led by Prof. Charlotte K. Williams at the University of Oxford developed a step-growth polymerization method that self-consumed CO2. The work has been published in a recent issue of Chemical Communications.

The synthesis involved two catalytic cycles (Figure 1). The first cycle polymerized L-lactide-O-carboxyanhydride into poly(L-lactide acid) (PLLA) via a ring-opening polymerization and released one CO2 molecule per polymer repeat unit. In the second cycle, epoxide molecules (cyclohexeneoxide) combined with the CO2 generated in the first step and grew into poly(cyclohexene carbonate) (PCHC) from the terminal ends of the PLLA chains. A di-zinc-alkoxide compound catalyzed both cycles and coupled the two processes together. The product is PLLA-b-PCHC block copolymers, which are composed of PLLA and PCHC covalently tethered together.

Figure 1. The two catalytic cycles are joined by a zinc-based catalyst, [LZn2(OAc)2]. The CO2 gas produced in the first step serves as a reactant in the second step. OCA: O-carboxyanhydride; ROP: ring-opening polymerization; CHO: cyclohexeneoxide; ROCOP: ring-opening copolymerization.

The two reactions resulted in block copolymers with few byproducts. In-situ 1H NMR revealed that the reactants in the first step (LLAOCA) were rapidly consumed during the first four hours (Step I, Figure 2a), and the concentration of PLLA increased notably. The concentration of PCHC only markedly increased after the concentration of PLLA saturated (Step II, Figure 2a). The byproduct of the second step, trans-cyclohexene carbonate, exhibited consistently low concentrations. The pronounced single peak in each size-exclusion chromatogram of the corresponding product confirmed the presence of block copolymers, instead of polymer mixtures (Figure 2b). Although the authors did not fully elucidate the origin of the excellent selectivity towards the block copolymer, they speculated that the change in CO2 partial pressure played a role. Significantly, nearly all CO2 molecules were consumed in the second step, with 91% incorporated into the block copolymer, and 9% converted to the byproduct.

Figure 2. (a) The evolution of the concentrations of PLLA, PCHC, and trans-CHC (the byproduct of the second step) with reaction time. (b) Size-exclusion chromatograms of the products at different reaction times. Mn: number-average molecular weight; Đ: polydispersity.

The authors are investigating the detailed polymerization mechanism, as well as identifying new catalysts to expand the polymerization scheme to other polymers.

 

To find out more, please read:

Waste Not, Want Not: CO2 (Re)cycling into Block Copolymers

Sumesh K. Raman, Robert Raja, Polly L. Arnold, Matthew G. Davidson, and Charlotte K. Williams

Chem. Commun., 2019, 55, 7315-7318

 

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Chemistry from University of California, Santa Cruz in the United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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4th Annual UK Porous Materials Conference

The Annual UK Porous Materials Conference (UKPorMat), now in its 4th year, was held at Cardiff University on the 1st and 2nd of July 2019. The meeting, organised and chaired by the committee members of the RSC Porous Materials Interest Group, aims to bring together researchers working in the expanding field of porous materials, which includes metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), porous organic cages, porous organic polymers, polymers of intrinsic microporosity and much more.

The Royal Society of Chemistry was delighted to be a part of the event, sponsoring a number of poster and talk prizes:

  • Giulia Schukraft (Imperial College London) was awarded the ChemComm Poster Prize
  • Iona Doig (University of Southampton) was awarded the Materials Horizons Poster Prize
  • Alexander Thom (University of Glasgow) was awarded the CrystEngComm Poster Prize
  • Alex James (University of Sheffield) was awarded the Chemical Science Prize for Best Talk

Congratulations to all of the prize winners!

 

Giulia Schukraft (left) receiving the ChemComm prize from Chris Harding (right)

Iona Doig (right) receiving the Materials Horizons prize from Chris Harding (left)

Alexander Thom (left) receiving the CrystEngComm prize from Ross Forgan (right) Alex James (left) receiving the Chemical Science prize from Chris Harding (right)

Special thanks to the organizers and committee members of the RSC Porous Materials Interest Group:

Dr Thomas Bennett (University of Cambridge)

Dr Andrea Laybourn (University of Nottingham)

Dr Ross Forgan (University of Glasgow)

Dr Darren Bradshaw (University of Southampton)

Dr Tim Easun (Cardiff University)

Dr Timothy Johnson (Johnson Matthey Technology Centre)

Professor Tina Düren

Prize-winners at the close of the 4th Annual UK Porous Materials meeting (Cardiff, 1st-2nd July 2019)

 

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