Archive for the ‘Uncategorized’ Category

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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Paper of the month: Enzyme-responsive polymeric micelles with fluorescence fabricated through aggregation-induced copolymer self-assembly for anticancer drug delivery

Yan et al. develop new enzyme-responsive polymeric micelles with potential applications in cancer therapy.

image describing the work

One of the most exciting and fast-growing topics in polymer chemistry is the synthesis of amphiphilic copolymers that can self-assemble into nanoparticles. Hydrophobic compounds such as cancer drugs can be encapsulated in the core of these self-assembled nanoparticles, thus protecting them from degradation or unwanted interactions with healthy cells. In addition, advances in polymer end-group functionalization allow the conjugation of special ligands on the nanoparticle surface which are responsible for directing the nanoparticles to cancer cells. Upon reaching the tumours (or being taken up by cancer cells), the nanoparticles must release the encapsulated drugs in order to kill the cancer cells. This drug release step requires the use of stimuli-responsive smart polymers that can switch from hydrophobic to hydrophilic upon exposure to stimuli. Temperature, pH, and enzyme-responsive polymers are therefore developed to release drugs on-demand. In this work, Zhao and co-workers further advance the field by synthesizing new fluorescent nanoparticles which can release a cancer drug (doxorubicin) while simultaneously turning off the fluorescent signal when the drug is released. This was achieved by efficiently coupling a tetraphenylethene moiety onto poly(acrylic acid). The hydrophobic property of the tetraphenylethene moiety induces the self-assembly of the resulting diblock copolymers into fluorescent nanoparticles via an aggregation-induced self-assembly mechanism. Upon exposure of the fluorescent nanoparticles to esterase, this enzyme can hydrolyze the ester bond between the tetraphenylethene side chain and the polymer backbone. The enzyme-catalyzed hydrolysis reaction turns the hydrophobic block back to the water-soluble poly(acrylic acid) block and therefore, disassembles the nanoparticles and also turns the fluorescent signal off. The diblock copolymer has poly(ethylene glycol) as the corona-forming block which possesses negligible toxicity to healthy cells. Therefore, this new copolymer is very promising for drug delivery applications, especially when monitoring the drug release is essential.

Citation to the paper: Visible light enabled para-fluoro-thiol ligation, Polym. Chem., 2020, 11, 7704-7713, DOI: 10.1039/D0PY01328E

Link to the paper: https://pubs.rsc.org/en/content/articlepdf/2020/py/d0py01328e

Professor Athina Anastasaki Dr. 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: Direct laser writing of poly(phenylene vinylene) on poly(barrelene)

Bielawski and co-workers report the ROMP of barrelene monomer affording precisely defined fluorescent patterns with micrometer-sized dimensions.

 

 

Conjugated polymers have attracted considerable attention owing to their abilities to form films and exhibit high electrical conductivities and as such they have found use in a range of electronic and optical applications. Amongst the various types of polymers, poly(phenylene vinylene) (PPV) is an excellent candidate due to its low optical band gap, large nonlinear optical response, and emissive properties. However, this material is typically intractable and thus challenging to process. To overcome this, Bielawski and co-workers designed a new approach to PPV was through the ring-opening metathesis polymerization (ROMP) of “barrelene” (bicyclo[2.2.2]octa-2,5,7-triene). The monomer was characterized for the first time by X-ray diffraction analysis of a coordination complex. Barrelene was subsequently homopolymerized and copolymerized with norbornene. The solubility of barrelene homopolymers was found to depend on the cis to trans ratio of alkene in its backbone. Both the homo and copolymers were transformed to PPV by undergoing spontaneous dehydrogenation under air. The materials were analyzed by a range of spectroscopic techniques. Importantly, direct laser writing of the barrelene-containing copolymers was also demonstrated resulting in thermal aromatization within a few seconds affording precisely defined fluorescent patterns with micrometer-sized dimensions. An intrinsic advantage of this development is that the monomer can be potentially incorporated into different macromolecular scaffolds and at varying compositions. Owing to this unique characteristic, the authors envision that their designed strategy would enable the synthesis of a broad range of materials for use in laser machining and contemporary lithography applications.

 

Tips/comments directly from the authors:

 

1)  The solubility of poly(barrelene) is dependent on the cis-to-trans ratio of the exocyclic olefins in the polymer backbone. Polymers with relatively high cis olefin contents appear to be more soluble than their trans isomers.

2)  The resolution of the patterns created by direct laser writing appear to be inversely proportional to the barrelene content of the copolymer used and may be enhanced further by increasing the transparency of the films.

3)  Poly(barrelene) oxidizes in air (slow) or upon laser irradiation (fast). A convenient way to monitor the oxidation reaction is through fluorescence spectroscopy. The starting material is non-emissive whereas the poly(phenylene vinylene) product emits a fluorescent green color upon excitation.

4)  Because barrelene is strained, copolymerization with other monomers used in ring-opening metathesis polymerization methodologies can be expected which, in turn, may expand the utility of the direct laser writing technique.

 

Citation to the paper: Direct laser writing of poly(phenylene vinylene) on poly(barrelene), Polym. Chem., 2020, 11, 5437-5443, DOI: 10.1039/d0py00869a

 

Link to the paper:

https://pubs.rsc.org/en/content/articlepdf/2020/py/d0py00869a

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: Single-chain crosslinked polymers via the transesterification of folded polymers: from efficient synthesis to crystallinity control

Terashima and co-workers report efficient synthetic systems of single-chain crosslinked polymers.

 

Crosslinked polymers have emerged as a class of unique materials which find use in a diverse range of applications such as drug delivery, dispersants and coating industries. Typically, those materials are made through a combination of controlled polymerization and crosslinked methods. In this work, Terashima and co-workers prepared a range of single-chain crosslinked polymers with controlled crystallization. This was achieved by the intramolecular transesterification of random copolymers compromising of octadecyl methacrylate, 2-hydroxyethyl methacrylate, and methyl acrylate. Those copolymers were self-folded in organic media (octane was used as the solvent) through the association of the hydroxyl groups to form reverse micelles. Upon synthesis, the micelles were intramolecularly crosslinked by an efficient transesterification of the methyl acrylate units with the hydroxyl groups to produce polymer nanoparticles with pending octadecyl groups. The materials synthesized were thoroughly characterized by a number of techniques including nuclear magnetic resonance, gel permeation chromatography, small angle X-ray scattering and dynamic light scattering. The developed system allowed for the efficient control of the molecular weight of the crosslinked polymers owing to the precise synthesis of the precursors prepared by living radical polymerization. Importantly, the degree of crosslinking was found to control the crystallinity of the products. Last but not least, a relatively high concentration could be used (up to 50 mg ml-1).  As the authors allude to in their conclusion, their work has paved the way to the production of well-defined polymeric nanoparticles that can be employed for surface coating, painting, optical plastics and cosmetics.

 

Tips/comments directly from the authors:

 

1) Intramolecular crosslinking of folded polymers in organic media via transesterification affords the precision and high-throughput synthesis of single-chain crosslinked polymer nanoparticles.

2) The molecular weight of the crosslinked polymers can be controlled as desired at the stage of the synthesis of the precursor polymers by controlled radical polymerization.

3) Transesterification between hydroxyl groups and methyl acrylate units efficiently proceeds within the cores of folded micelles to fix the folded structures in a specific solvent.

4) SEC-MALLS analysis is essential to characterize single-chain crosslinked polymers. Because of the compact structures, the apparent molecular weight of the crosslinked polymers by the general RI detector with PMMA standard calibration turns smaller than that of the non-crosslinked precursor polymers. If the absolute weight-average molecular weight of the crosslinked polymers by the MALLS detector is also close to that of the precursor polymers, you can conclude that the products consist of single chain-crosslinked polymers.

5) Crystallinity of the bulk polymers is controlled by tuning the degree of intramolecular crosslinking. This is an interesting approach to control the thermal and physical properties of solid polymer materials.

Citation to the paper: Single-chain crosslinked polymers via the transesterification of folded polymers: from efficient synthesis to crystallinity control, Polym. Chem., 2020, 11, 5181-5190, doi.org/10.1039/D0PY00758G

Link to the paper: https://pubs.rsc.org/en/content/articlepdf/2020/py/d0py00758g

About the web writer:

Professor Athina Anastasaki

Dr. 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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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: April Kloxin

April M. Kloxin, Ph.D., is an Associate Professor in Chemical & Biomolecular Engineering and Materials Science & Engineering at the University of Delaware (UD) and a member of the Breast Cancer Research Program at the Helen F. Graham Cancer Center and Research Institute in the Christiana Care Health System.  She obtained her B.S. and M.S. in Chemical Engineering from North Carolina State University and Ph.D. in Chemical Engineering from the University of Colorado, Boulder, as a NASA Graduate Student Research Program Fellow.  She trained as a Howard Hughes Medical Institute postdoctoral research associate at the University of Colorado before joining the faculty at UD in 2011. Her group aims to create unique materials with multiscale property control for addressing outstanding problems in human health. Her research currently focuses on the design of responsive and hierarchically structured soft materials and development of controlled, dynamic models of disease and regeneration.  Her honors include the Biomaterials Science Lectureship 2019, ACS PMSE Arthur K. Doolittle Award 2018, a Susan G. Komen Foundation Career Catalyst Research award, a NSF CAREER award, and a Pew Scholars in Biomedical Sciences award.

What was your inspiration in working with polymers?

I have always enjoyed building things and had a desire to use those skills to help people.  I discovered my passion for using chemical approaches to build soft polymeric materials possessing unique and useful properties as an undergraduate and Master’s student at North Carolina State University (NCSU).  At NCSU, I had the opportunity to work in a collaborative environment with many extraordinary friends and colleagues having great polymer science and engineering expertise, including my MS thesis advisors Profs. Rich Spontak and Stuart Cooper.  This experience helped me understand the connection between molecular design and synthetic approaches for building polymeric materials with specific properties for a desired application.  I had the opportunity to fully realize and direct this passion working at the interface between polymeric materials and biological systems under the outstanding advisement and mentorship of Prof. Kristi Anseth at the University of Colorado, Boulder, for my Ph.D. and with the many remarkable researchers in her group and at the University.


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

From a biological perspective, my group has a focus on understanding how changes in the structure, mechanical properties, and compositions of tissues in the human body that occur upon injury influence the function and fate of key cells in healing and disease.  In this context, we have been interested in building synthetic mimics of these complex systems and processes, and we wanted to establish simple yet effective approaches for controlling the density and stiffness of soft materials when and where desired for hypothesis testing.  In the Polymer Chemistry manuscript, we were inspired by the work of Prof. Matt Becker (Duke University) amongst others demonstrating how the rate of formation of water-swollen polymer networks, hydrogels, could be used to control defect formation, network heterogeneity, and thereby the mechanical properties of the resulting materials.  We hypothesized that the rate-based control of properties that others observed with catalyzed step growth reactions was translatable to a photo-polymerized system, affording the implementation of a variety of photochemical controls (e.g., wavelength, intensity, time).  In particular, by selecting a wavelength of light that was not centered at the maximum absorption of the photoinitiator, we were better able to control the rate of photopolymerization with an accessible bench-top visible light LED system and thereby defect formation.  We then saw an opportunity to exploit dangling-end defects that were generated with this rate-based approach to increase crosslink density and ‘stiffen’ these materials with a secondary photopolymerization.  We are excited about the potential that this light-triggered rate-based approach for controlling mechanical properties of polymer networks has for a number of applications, including our on-going studies of cell response to matrix stiffening.


Which polymer or materials scientists are you most inspired by?

Oh, there are so many! I am especially inspired by the work and leadership of Prof. Paula Hammond (MIT) and Prof. Kristi Anseth, who continue to blaze trials at the interface between polymers, materials, and biology to solve complex problems, and Prof. Chris Bowman (University of Colorado, Boulder) and the late Prof. Charlie Hoyle (University of Southern Mississippi), who have pioneered the use of light-triggered step growth reactions for creating polymeric materials with diverse and robust properties.


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

It is an exciting time in polymer chemistry with many excellent researchers working from different perspectives to advance not only the field of polymer chemistry, but also to make fundamental breakthroughs that have an impact in biology, medicine, and energy.  Selecting just a few is difficult in this context.  A few that come to mind at the moment whose work I find particularly inspiring are Prof. Aaron Esser Kahn (University of Chicago) in biomolecular design of polymeric materials for rewiring the immune system, Prof. Dominik Konkolewicz (Miami University Ohio) in bioconjugations and dynamic covalent chemistries with polymeric materials, Prof. Rachel A. Letteri (University of Virginia) in peptide-polymer conjugates for multi-scale and dynamic properties, and my own new colleague Prof. Laure Kayser (University of Delaware) in conducting and semiconducting polymers.


How do you spend your spare time?

I enjoy making things, from designing materials at work to preparing satisfying meals in the kitchen at home.  Breakfast foods are my favorite, and I have different recipes that I continue to hone on weekends for quick meals during the week.  I also love being outside walking, hiking, or running with my friends or my husband and our two sons, particularly in the beautiful early autumn weather we currently are having.


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

My obsession with the complexity of biological systems and improving human health would keep me in science and engineering, whether in molecular biology or bioinformatics or more applied in medicine.

 

Read April’s recent Polymer Chemistry article now for FREE until 31st October!


Rate-based approach for controlling the mechanical properties of ‘thiol–ene’ hydrogels formed with visible light

 

The mechanical properties of synthetic hydrogels traditionally have been controlled with the concentration, molecular weight, or stoichiometry of the macromolecular building blocks used for hydrogel formation. Recently, the rate of formation has been recognized as an important and effective handle for controlling the mechanical properties of these water-swollen polymer networks, owing to differences in network heterogeneity (e.g., defects) that arise based on the rate of gelation. Building upon this, in this work, we investigate a rate-based approach for controlling mechanical properties of hydrogels both initially and temporally with light. Specifically, synthetic hydrogels are formed with visible light-initiated thiol–ene ‘click’ chemistry (PEG-8-norbornene, dithiol linker, LAP photoinitiator with LED lamp centered at 455 nm), using irradiation conditions to control the rate of formation and the mechanical properties of the resulting hydrogels. Further, defects within these hydrogels were subsequently exploited for temporal modulation of mechanical properties with a secondary cure using low doses of long wavelength UV light (365 nm). The elasticity of the hydrogel, as measured with Young’s and shear moduli, was observed to increase with increasing light intensity and concentration of photoinitiator used for hydrogel formation. In situ measurements of end group conversion during hydrogel formation with magic angle spinning (MAS 1H NMR) correlated with these mechanical properties measurements, suggesting that both dangling end groups and looping contribute to the observed mechanical properties. Dangling end groups provide reactive handles for temporal stiffening of hydrogels with a secondary UV-initiated thiol–ene polymerization, where an increase in Young’s modulus by a factor of ∼2.5× was observed. These studies demonstrate how the rate of photopolymerization can be tuned with irradiation wavelength, intensity, and time to control the properties of synthetic hydrogels, which may prove useful in a variety of applications from coatings to biomaterials for controlled cell culture and regenerative medicine.

 


About the Webwriter

Simon HarrissonSimon Harrisson is a Chargé de Recherche at the Centre National de la Recherche Scientifique (CNRS), based in the Laboratoire des IMRCP in Toulouse. 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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Outstanding Reviewers for Polymer Chemistry in 2018

Outstanding Reviewers for Polymer Chemistry in 2018

We would like to highlight the Outstanding Reviewers for Polymer Chemistry in 2018, as selected by the editorial team, for their significant contribution to the journal. The reviewers have been chosen based on the number, timeliness and quality of the reports completed over the last 12 months.

We would like to say a big thank you to those individuals listed here as well as to all of the reviewers that have supported the journal. Each Outstanding Reviewer will receive a certificate to give recognition for their significant contribution.

Professor Cyrille Boyer, University of New South Wales ORCiD: 0000-0002-4564-4702

Dr Sophie Guillaume, Institut des Sciences Chimiques de Rennes ORCiD: 0000-0003-2917-8657

Dr Xiaoyu Huang, Shanghai Institute of Organic Chemistry ORCiD: 0000-0002-9781-972X

Professor Dominik Konkolewicz, Miami University ORCiD: 0000-0002-3828-5481

Dr Vincent Ladmiral, ICGM ORCiD: 0000-0002-7590-4800

Dr Zachariah Page, University of Texas at Austin ORCiD: 0000-0002-1013-5422

Professor Felix Schacher, Friedrich Schiller University Jena ORCiD: 0000-0003-4685-6608

Professor Takeshi Shinono, Hiroshima University ORCiD: 0000-0002-1118-9991

Professor Lin Yuan, Soochow University ORCiD: 0000-0001-6966-8584

Professor Youliang Zhao, Soochow University ORCiD: 0000-0002-4362-6244

We would also like to thank the Polymer Chemistry board and the research community for their continued support of the journal, as authors, reviewers and readers.

If you would like to become a reviewer for our journal, just email us with details of your research interests and an up-to-date CV or résumé.  You can find more details in our author and reviewer resource centre

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European Biopolymer Summit 2019

The 6th Edition of ACI’s European Biopolymer Summit will be taking place on 13th – 14th February 2019 in Ghent, Belgium.

The two day event specially designed to bring together senior executives, key industry experts, researchers and bioplastic manufacturers, to exchange and share their experiences and research results on all aspects of bioenvironmental polymer engineering, most recent innovations, trends and concern as well as solutions adopted in the sector.

Key topics include:

  • Evaluating Current Environmental Projects And Regulations Within The Biopolymer Industry
  • Assessing The Feedstock’s Landscape For The Biopolymers’ Production
  • Focusing On Biopolymers in The Circular Economy
  • Elaborating On The Application Of Biopolymers From Peoples’ And Planet’s Perspective
  • Introducing New Technologies In Processing New Bio-Based Materials
  • Brand Owners Perspective On The Use And Application Of Biopolymers
  • Focusing On The Basic Understanding Of Biodegradability
  • Assessing The Biobased New Content
  • Analysing The Impact Of Biobased Plastics On The CO2 Reduction
  • Changing Consumer Preference Towards Eco-Friendly Packaging
  • Assessing The End-Of-Life Of Materials, Through The Life Cycle Assessment

A £255 discount is available for all participants until January 31st. Register now

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Focus on: Antimicrobial polymers

Antimicrobial agents kill or inhibit the growth of microorganisms, and can be sub-divided into several classes depending on the type of microorganism they target. Sub-divisions include, antibacterial, antifungal, antiviral and antiparasitic agents. In particular, antibacterial agents are incredibly important worldwide, with the emergence of multi-drug resistant bacteria. Antibiotic-resistant infections are becoming an increased health and economic burden on society. As such the development of new antibacterials continues to be paramount to limiting the spread of multi-drug resistant bacteria.

This month we focus on three articles published in Polymer Chemistry which have reported the use of antimicrobial polymers. In each case the polymers reported have antibacterial properties, and in one article polymers were also investigated for their antifungal properties.

 

 

1. Cationic peptidopolysaccharides synthesized by ‘click’ chemistry with enhanced broad-spectrum antimicrobial activities
Yajuan Su, Liang Tian, Meng Yu, Qiang Gao, Dehui Wang, Yuewei Xi, Peng Yang, Bo Lei, Peter X. Ma, Peng Li
Polym. Chem., 2017, 8, 3788-3800; DOI: 10.1039/C7PY00528H

Cationic peptidopolysaccharides were prepared through the grafting of ε-poly-L-lysine (EPL) to a chitosan (CS) backbone by thiol-ene “click” chemistry. The resulting CS-g-EPL polymers were assessed for their antimicrobial activity against Gram negative bacteria, Gram positive bacteria and fungi, which showed broad-spectrum antimicrobial activity. In addition the hemolytic activity of the polymers was determined, and the lead candidate was further investigated for it’s biocompatability.

2. Astaxanthin-based polymers as new antimicrobial compounds
S. Weintraub, T. Shpigel, L. G. Harris, R. Schuster, E. C. Lewis, D. Y. Lewitus
Polym. Chem., 2017, 8, 4182-4189; DOI: 10.1039/C7PY00663B

Astaxanthin (ATX) is an organic pigment produced by fungi and algae, possessing various therapeutic properties. Polyesters were prepared using carbodiimide-mediated coupling of ATX, which is a diol, with alkyl- and PEG-diacids. The diacid used influenced the resulting physico–chemical–mechanical properties of the polymers. Antibacterial activity was observed against three strains of bacteria, including MRSA, and the materials were found to be non-toxic in an in vivo wound healing model.

3. Bio-inspired peptide decorated dendrimers for a robust antibacterial coating on hydroxyapatite
Yaping Gou, Xiao Yang, Libang He, Xinyuan Xu, Yanpeng Liu, Yuebo Liu, Yuan Gao, Qin Huang, Kunneng Liang, Chunmei Ding, Jiyao Li, Changsheng Zhao, Jianshu Li
Polym. Chem., 2017, 8, 4264-4279; DOI: 10.1039/C7PY00811B

The authors report the use of a salivary statherin protein inspired dendrimer, for use as an antibacterial coating for implanted biomaterials. A peptide sequence was coupled to the surface of a G4 PAMAM dendrimer, by Michael addition. The materials showed adsorption to hydroxyapatite surfaces with sufficient binding strength to survive washing. The adsorbed dendrimers endowed antimicrobial properties observed by an inhibition of biofilm formation and through in vivo experiments.

 

Read these articles for free until September 10th


About the webwriterFiona Hatton

Dr. Fiona Hatton is a web writer for Polymer Chemistry. She is currently a postdoctoral researcher in the Armes group at the University of Sheffield, UK. Find her on Twitter: @fi_hat

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