Archive for July, 2017

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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Paper of the month: Acceleration and improved control of aqueous RAFT/MADIX polymerization of vinylphosphonic acid in the presence of alkali hydroxides

Phosphonic acid functionalized polymers find use in a wide range of applications such as metal protection, polymer electrolyte membranes flame retardancy and dentistry. This is thanks to their unique characteristics including their acidic nature, stability, proton conductivity and metal binding ability. Vinyl phosphonic acid (VPA) in particular is a structurally simple example of such monomers which is not only affordable but also provides with a polymer (PVPA) with phosphonic acid groups that are directly attached to the backbone.

 

 

Despite the popularity and applicability of this polymer, the polymerization of VPA is typically slow yielding incomplete conversions which necessitates the need for additional costly and time-consuming purification steps. Destarac, Harrisson and co-workers were capable to circumvent this by investigating the effect of adding various alkali hydroxides to the conventional (free radical) and reversible addition-fragmentation transfer polymerization/macromolecular design by interchange of xanthates (RAFT/MADIX) radical polymerizations. Both types of polymerizations were strongly affected by the addition of NaOH. The authors found that by adding 1 equivalent of NaOH they could significantly increase the rate of the polymerization and the final conversion for both conventional and RAFT/MADIX polymerizations while larger quantities led to retardation of the reaction. A wide range of alkali hydroxides were also studied including H+, Li+, K+ and NH4+. It was shown that the dispersity of the final polymer decreases as the ionic radius of the counterion increases (H+ > Li+> Na+ > K+ > NH4+) while the acceleration of the polymerization follows the order Na+ > K+ > NH4+> Li+ > H+). Overall, the fastest rates of polymerizations were obtained in the presence of 0.5 equivalent of NaOH, while the same concentration of KOH or NH4OH allowed for a moderate acceleration on the polymerization rate combined with an improved control over the molar masses. Thus, this simple and cost-effective strategy can significantly improve the efficiency of the polymerization of VPA by simultaneously enhancing the reaction rate and the control over the molar masses.

 

 

Tips/comments directly from the authors:

  1. Take care to control the temperature when neutralizing the VPA – the reaction is very exothermic!
  2. Use NaOH for the most significant acceleration of polymerization and NH4OH for the strongest reduction in dispersity of the polymer.
  3. PVPA homopolymer can be precipitated in MeOH, but many PVPA-containing DHBCs must be purified by dialysis due to the small difference in solubility between PVPA and VPA and the low volatility of VPA.

 

Read this exciting research for free until 10/09/2017 through a registered RSC account.

Acceleration and improved control of aqueous RAFT/MADIX polymerization of vinylphosphonic acid in the presence of alkali hydroxides
Polym. Chem., 2017, 8, 3825-3832, DOI: 10.1039/c7py00747g

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About the webwriterAthina Anastasaki

Dr. Athina Anastasaki is a web writer for Polymer Chemistry. She is currently a Global Marie Curie Fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please visit this website for more

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8th Symposium on Controlled Radical Polymerization

American Chemical Society, Chemistry for Life ®

 

Polymer Chemistry is pleased to be sponsoring the 8th Symposium on Controlled Radical Polymerization, held during this year’s ACS Fall Meeting in Washington, DC and organised by Brent SumerlinHaifeng Gao, Krzysztof Matyjaszewski and Nicolay Tsarevsky.

The symposium, which will take place on Sunday 20 August, will also feature a talk from Polymer Chemistry 2017 Lectureship winner Dr Julien Nicolas, as well as sessions on:

  • New macromolecular architectures and new ATRP initiating systems
  • Kinetics of radical polymerizations deduced via SP-PLP-EPR
  • RAFT 20 years later: Elements of RAFT navigation
  • Ionic auxiliaries for stereocontrolled radical polymerization
  • Mechanistic studies of transition metal catalyzed radical termination
  • Living radical polymerization using organic catalysts: Synthesis and applications
  • Electrochemistry for ATRP
  • Iron mediated controlled radical polymerisation
  • Designer polymers from palladium-catalyzed cross-coupling reactions

Registration for this event is now open – please visit the ACS website to register.

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Welcoming our new Polymer Chemistry Editor-in-Chief

We are excited to welcome new Editor-in-Chief Christopher Barner-Kowollik (Queensland University of Technology) to the Polymer Chemistry Editorial Board

 

 

Prof. Barner-Kowollik

Christopher Barner-Kowollik is Professor of Materials Science and head of the Soft Matter Materials Laboratory at the Queensland University of Technology. He has published over 510 peer-reviewed studies and won several awards for his research, most recently the coveted Erwin-Schrödinger Award of the Helmholtz association (2016) and a Laureate Fellowship from the Australian Research Council (2017).

His main research interests are situated at the interface of organic, polymer and biochemistry and focus on a wide range of polymer-related research fields, such as the (photochemical) synthesis of complex macromolecular architectures with highly-defined functionality and composition, advanced synthesis via polymer ligation techniques and macromolecular transformations at ambient temperature in solution and on surfaces, with a strong focus on light-induced methodologies, advanced photolithographic processes, fundamental investigations into polymerization mechanisms and kinetics, as well as high resolution imaging and characterization of macromolecular chain structures via mass spectrometric methods in solution and on surfaces.

 

Christopher has been an Associate Editor for Polymer Chemistry since 2009, and we are delighted that he has agreed to become our new Editor-in-Chief! Welcome to the new position!

Christopher takes over from Professor David Haddleton, who has led the journal since its launch in 2009. We would like to thank Professor Haddleton for his excellent work as Editor-in-Chief and will be delighted to continue working with him as an Advisory Board member.

As Polymer Chemistry Editor-in-Chief, Christopher will be handling submissions to the journal. Why not submit your next paper to his Editorial Office?

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