Archive for the ‘Paper of the Week’ Category

Paper of the week: Functional α,ω-dienes via thiol-Michael chemistry

The preparation of functional α,ω-dienes via thiol-Michael chemistry including synthesis, oxidative protection, acyclic diene metathesis (ADMET) polymerization and radical thiol–ene modification has been reported by Lowe et al.


The synthesis of the novel α,ω-diene 2-(undec-10-en-1-yl)tridec-12-en-1-yl acrylate is described. Thiol-Michael coupling of this substrate followed by chemoselective oxidation of the thioether moiety with triazotriphosphorine tetrachloride (TAPC) furnished a suite of functional and symmetrical ADMET-active monomers in a quick and convenient manner. Polymerization of these adducts with Grubbs 1st generation catalyst (RuCl2(PCy3)2CHPh) was demonstrated to high conversion, and quantitative radical initiated thiol–ene modification of the backbone C[double bond, length as m-dash]C bonds was performed to impart additional functionality to each ADMET polymer. These reactions highlight the compatibility of thiol-based click chemistries for the preparation and post-modification of functional ADMET materials.

Functional α,ω-dienes via thiol-Michael chemistry: synthesis, oxidative protection, acyclic diene metathesis (ADMET) polymerization and radical thiol–ene modification by Johannes A. van Hensbergen, Taylor W. Gaines, Kenneth B. Wagener, Robert P. Burford and  Andrew B. Lowe Polym. Chem., 2014, 5, 6225-6235.

Remzi Becer is a web-writer and advisory board member for Polymer Chemistry. He is currently a Senior Lecturer in Materials Science and the director of the Polymer Science and Nanotechnology masters programme at Queen Mary, University of London. Visit www.becergroup.com for more information.

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Paper of the week: Ethanol biosensors based on conducting polymers with peptide and ferrocene on the side chain

The synthesis and characterization of conducting polymers containing polypeptide and ferrocene side chains as ethanol biosensors has been reported by Yagci and Toppare et al.

This paper describes a novel approach for the fabrication of a biosensor from a conducting polymer bearing polypeptide segments and ferrocene moieties. The approach involves the electrochemical copolymerization of the electroactive polypeptide macromonomer and independently prepared ferrocene imidazole derivative of dithiophene, on the electrode surface. The polypeptide macromonomer was synthesized by the simultaneous formation of N-carboxyanhydride (NCA) and ring opening polymerization of N-Boc-L-lysine (α-amino acid of the corresponding NCA) using an amino functional bis-EDOT derivative (BEDOA-6) as an initiator. Alcohol oxidase was then covalently immobilized onto the copolymer coated electrode using glutaraldehyde as the crosslinking agent. The intermediates and final conducting copolymer before and after enzyme immobilization were fully characterized by FT-IR, 1H-NMR, GPC, cyclic voltammetry, SEM and EIS analyses. The newly designed biosensor which combined the advantages of each component was tested as an ethanol sensing system offering fast response time (9 s), wide linear range (0.17 mM and 4.25 mM) and low detection limit (0.28 mM) with a high sensitivity (12.52 μA mM−1 cm−2). Kinetic parameters KappM and Imax were 2.67 mM and 2.98 μA, respectively. The capability of the biosensor in determining ethanol content in alcoholic beverages was also demonstrated.

Synthesis and characterization of conducting polymers containing polypeptide and ferrocene side chains as ethanol biosensors by Melis Kesik, Huseyin Akbulut, Saniye Söylemez, Şevki Can Cevher, Gönül Hızalan, Yasemin Arslan Udum, Takeshi Endo, Shuhei Yamada, Ali Çırpan, Yusuf Yağcı and Levent Toppare Polym. Chem., 2014, 5, 6295-6306.

Remzi Becer is a web-writer and advisory board member for Polymer Chemistry. He is currently a Senior Lecturer in Materials Science and the director of the Polymer Science and Nanotechnology masters programme at Queen Mary, University of London. Visit www.becergroup.com for more information.

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Paper of the week: Zwitterionic poly(2-oxazoline)s for blood-contacting applications

The synthesis of highly hemo- and cytocompatible zwitterionic 2-oxazoline-based poly(sulfobetaine)s and poly(carboxybetaine)s, which demonstrate beneficial anticoagulant activity, has been reported by Schubert et al.

The polymers were obtained by thiol–ene photoaddition of a tertiary amine-containing thiol onto an alkene-containing precursor copoly(2-oxazoline), followed by betainization with 1,3-propansultone and β-propiolactone. The polymers and their intermediates were characterized by means of 1H NMR spectroscopy and size exclusion chromatography. The influence of the zwitterionic polymers on the aggregation and hemolysis of erythrocytes, the whole blood viscosity, the platelet and complement activation as well as the blood coagulation has been studied in detail. In addition, the cytotoxicity of the materials has been evaluated.

It was found that the zwitterionic POx show no negative interactions with blood. Moreover, anticoagulant activity via the intrinsic and/or the common coagulation pathway was observed. The high hemocompatibility and the low cytotoxicity as well as the beneficial anticoagulant activity of the presented zwitterionic poly(2-oxazoline)s demonstrate their potential for the use in biomedical applications.

Zwitterionic poly(2-oxazoline)s as promising candidates for blood contacting applications by Lutz Tauhardt, David Pretzel, Kristian Kempe, Michael Gottschaldt, Dirk Pohlers and  Ulrich S. Schubert Polym. Chem. 2014, 5, 5751-5764.

Remzi Becer is a web-writer and advisory board member for Polymer Chemistry. He is currently a Senior Lecturer in Materials Science and the director of the Polymer Science and Nanotechnology masters programme at Queen Mary, University of London. Visit www.becergroup.com for more information!

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Paper of the week: Photoswitchable nanocomposites

‘Cellulose nanocrystals (CNCs) have gained significant attention in the past two decades, mainly due to their high axis-modulus, reinforcing ability in various polymer matrices, vast availability in a diverse range of natural sources such as cotton, wheat straw, wood, sisal, banana stems, ramie, tunicates, bacteria and ease of isolation via acid or enzymatic hydrolysis, and ultrasonic treatment. One of the interesting features of CNCs is that the hydroxyl groups on the surface can serve as a handle to impart CNC/polymer nanocomposites with water-responsive mechanically adaptive characteristics.’

Graphical abstract: Photoswitchable nanocomposites made from coumarin-functionalized cellulose nanocrystals

Exploiting the coumarin dimerization mechanism upon UV irradiation at 365 nm, Foster and co-workers developed mechanically adaptive nanocomposites in which light can be used to change the materials properties. CNCs derived from tunicates were functionalized with 7-coumaryl-(6-isocyanatohexyl) carbamate to afford coumarin-derivatized CNCs (Cou-CNCs). Light-responsive nanocomposites were prepared by reinforcing a rubbery ethylene oxide–epichlorohydrin copolymer (EO–EPI) matrix with Cou-CNCs. The as-prepared nanocomposites show a significantly increased tensile storage modulus (E′) in comparison to the neat EO–EPI. The optically induced reaction between Cou-CNCs also reduced the swelling of the EO–EPI/Cou-CNC nanocomposites upon exposure to water as well as the extent of water-induced softening.

Photoswitchable nanocomposites made from coumarin-functionalized cellulose nanocrystals by Mahesh V. Biyani, Christoph Weder and E. Johan Foster Polym. Chem. 2014, 5, 5501-5508.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: White light emission of multi-chromophore photoluminescent nanoparticles

‘Fluorescence is a powerful tool in a variety of applications, ranging from optical to analytical materials (detection of small molecules and protein studies) because of its exquisite sensitivity, cost-effectiveness, facile operation, and superb spatial and temporal resolutions. Fluorescent organic nanoparticles derived from conjugated polymers have attracted significant interest due to their variable optical, electronic, and other properties such as facile preparation and functionalization. Among conjugated polymers used in organic nanoparticles, polyfluorene (PF) and its derivatives are considered to be of special interest because of their thermal/chemical stability, high fluorescence quantum yield and significant charge carrier mobility.’

Graphical abstract: White light emission of multi-chromophore photoluminescent nanoparticles using polyacrylate scaffold copolymers with pendent polyfluorene groups

In this work, Ling, Hogen-Esch and co-workers reported a styrene-type macromonomer containing polyfluorene pendent group (PFS), which allowed the convenient synthesis of well-defined copolymers of PFS with t-butyl acrylate by both RAFT and ATRP polymerization methods. After hydrolysis, the amphiphilic copolymers self-assembled into photoluminescent nanoparticles in aqueous solution. When doped with selected dyes, the nanoparticles emitted light with tunable colors as well as white via Förster energy transfer from the excited pendent polyfluorene groups.

White light emission of multi-chromophore photoluminescent nanoparticles using polyacrylate scaffold copolymers with pendent polyfluorene groups by Chao Deng, Peng Jiang, Xiaobin Shen, Jun Ling and Thieo E. Hogen-Esch, Polym. Chem. 2014, 5, 5109-5115.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine used as a transdermal penetration enhancer

‘The stratum corneum (SC) of skin is the main barrier against transdermal drug penetration, and poor permeability in the SC limits the usefulness of the transdermal drug administration route. Generally, drug permeation through the SC could be increased with skin permeation enhancers. Currently, enhancers most frequently used in transdermal drug delivery systems are neatly divided into three categories. One is organic solvents such as ethanol, propylene glycol and dimethyl sulfoxide. The second is surfactants such as cationic, anionic and nonionic surfactants. The last category is laurocapram and its derivative series. Nevertheless, their potential shortcomings have gradually been recognized, for their great irritation to skin or causing harm to organs. The practical use of enhancers requires the careful balancing of skin toxicity and permeation enhancement benefits’

Graphical abstract: In vitro and in vivo application of hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine used as a transdermal penetration enhancer

In this work, Xing and co-workers developed a new penetration enhancer based on hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine (HP-β-CD–PEI). Its penetration mechanism relied on a change of the secondary structure of keratin in the stratum corneum to enhance the transcutaneous permeation of drugs. By using a series of in vitro and in vivo methods, this cationic polymer demonstrated great biocompatibility and could be valuable for topical delivery as a penetration enhancer to improve the penetration of hydrophilic drugs.

In vitro and in vivo application of hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine used as a transdermal penetration enhancer by Ke Wang, Yan Yan, Guilan Zhao, Wei Xu, Kai Dong, Cuiyu You, Lu Zhang and Jianfeng Xing, Polym. Chem. 2014, 5, 4658-4669.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Hybrid organic–inorganic copolymers with self-healing properties

‘Over the last decade, a broad range of self-healing materials has emerged. Such systems, when they have been damaged, heal themselves either spontaneously or with the aid of a stimulus. Several of these materials draw their inspiration from the design of biological materials. On the other hand, hybrid materials or nanocomposites, defined as composites constituted of two components, one inorganic and the other one organic in nature mixed at the nanometer level, have attracted strong interest both in academia and industry. The combination at the nanoscale of organic and inorganic components leads to highly homogeneous materials, which develop extended organic–inorganic interfaces with tuneable chemical organic–inorganic bonds from weak to strong interactions.’

Graphical abstract: Nano-building block based-hybrid organic–inorganic copolymers with self-healing properties

In this work, Rozes and co-workers prepared new dynamic materials, that can repair themselves after strong damage, by hybridization of polymers with structurally well-defined nanobuilding units. The controlled design of cross-linked poly(n-butyl acrylate) (PnBA) has been performed by introducing a very low amount of a specific tin oxo-cluster. Sacrificial domains with non-covalent interactions (i.e. ionic bonds) developed at the hybrid interface play a double role. Such interactions are strong enough to cross-link the polymer, which consequently exhibits rubber-like elasticity behavior, and labile enough to enable, after severe mechanical damage, dynamic bond recombination leading to an efficient healing process at room temperature. In agreement with the nature of the reversible links at the hybrid interface, the healing process can speed up considerably with temperature .

Nano-building block based-hybrid organic–inorganic copolymers with self-healing properties by F. Potier, A. Guinault, S. Delalande, C. Sanchez, F. Ribot and L. Rozes, Polym. Chem. 2014, 5, 4474-4479.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Cu(0)-mediated polymerization using high-throughput experimentation

‘Over the past decades, several types of controlled radical polymerization methods have been developed. The most popular methods are atom transfer radical polymerization (ATRP), reversible addition–fragmentation chain transfer (RAFT) polymerization and nitroxide mediated polymerization (NMP). One of the more recently developed techniques, which appears to be very promising, is Cu(0)-mediated polymerization, known variously as SET-LRP or SARA-ATRP. Recent publications have shown significant progress in the area of Cu(0)-mediated polymerization. Among the monomers that have been polymerized in a controlled manner via Cu(0)-mediated polymerization are acrylates, methacrylates, vinyl chloride and (meth)acrylamides. However, for each monomer the polymerization conditions should be optimized, which is in general a very time consuming task.’

Graphical abstract: Cu(0)-mediated polymerization of hydrophobic acrylates using high-throughput experimentation

In this work, Hoogenboom and co-workers report the optimization of the Cu(0)-mediated polymerization of n-butyl acrylate (BA) and 2-methoxyethyl acrylate (MEA) via Cu(0)-mediated polymerization using an automated parallel synthesizer.  Using this robot, up to 16 kinetic reactions could be performed in parallel, resulting in a fast screening of different reaction conditions. Several parameters were optimized to determine the optimal reaction conditions with regard to control over the polymerization and reaction rate. These optimal reaction conditions were then used for the one-pot two-step synthesis of diblock copolymers by sequential monomer addition. Altogether, this work shows the power of high-throughput optimization of Cu(0)-mediated polymerization reaction conditions. As such, it may serve to accelerate optimization of Cu(0)-mediated polymerization conditions and aid in gaining fundamental understanding of the effects of various parameters on the Cu(0)-mediated polymerization.

Cu(0)-mediated polymerization of hydrophobic acrylates using high-throughput experimentation by Lenny Voorhaar, Sofie Wallyn, Filip E. Du Prez and Richard Hoogenboom, Polym. Chem. 2014, 5, 4268-4276.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Fully biodegradable antibacterial hydrogels

‘Bacterial infection is a serious problem in many areas, especially those involving the use of biomaterials. According to World Health Organization (WHO) statistics, at any time, over 1.4 million people worldwide suffer from infectious complications acquired in hospital, which have much to do with the use of medical devices. Hydrogels are three-dimensional polymer networks that are able to retain a large fraction of aqueous solvent within their structures. Due to their high water content and soft consistency, which is similar to natural tissue, hydrogels resemble natural living tissue more than any other class of synthetic biomaterial. Therefore, hydrogels have received extraordinary attention as biomaterials for use in biomedical applications, such as tissue engineering, wound dressing materials, immunoisolation16 and drug delivery. Thus, fabricating hydrogels with antibacterial properties is crucial for the biomedical field.’

Graphical abstract: Fully biodegradable antibacterial hydrogels via thiol–ene “click” chemistry

In this work, Zhu and co-workers prepared fully biodegradable antimicrobial hydrogels via a thiol–ene “click” reaction under human physiological conditions using multifunctional poly(ethylene glycol) (PEG) derivatives as precursors. Water soluble and degradable PEG derivatives with multi-enes and multi-thiols, respectively, were synthesized by polycondensation of oligo(ethylene glycol) (OEG) with “clickable” monomers. Ammonium groups with long alkyl chains were incorporated into one of the precursors covalently, using dodecyl bis(2-hydroxyethyl) methylammonium chloride as a comonomer.  These types of cationic PEG-type hydrogels showed strong antibacterial abilities against both Gram- negative and Gram-positive bacteria due to the ammonium moieties. Moreover, the hydrogel with fewer ammonium moieties still possessed significant antibacterial abilities, but low toxicity, and has the potential to be used as a medical material.

Fully biodegradable antibacterial hydrogels via thiol–ene “click” chemistry by Hong Du, Guangyu Zha, Lilong Gao, Huan Wang, Xiaodong Li, Zhiquan Shena and Weipu Zhu, Polym. Chem. 2014, 5, 4002-4008.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Macroporous antibacterial hydrogels with tunable pore structures

‘Porous hydrogels with well-defined pore structure have attracted considerable attention due to their multifarious applications such as scaffolds for tissue engineering, vehicles for drug delivery and self-healing materials. CO2-in-water (C/W) high internal phase emulsions (HIPEs) and oil-in-water (O/W) HIPEs are considered as very effective templates to produce such kinds of high porosity hydrogels… In most cases, the O/W HIPEs are stabilized by large amounts of surfactants at high concentrations of 5–50 vol%, where the enormous quantity of surfactants presents economic and potential environmental problems. Therefore, much attention has been focused on the Pickering-HIPEs, which are stabilized by colloidal particles instead of traditional surfactants.’

Graphical abstract: Macroporous antibacterial hydrogels with tunable pore structures fabricated by using Pickering high internal phase emulsions as templates

In this work, Deng, Wang and co-workers prepared Artemisia argyi oil (AAO)-loaded macroporous antibacterial hydrogels by polymerization of oil-in-water Pickering HIPEs. The HIPEs were stabilized by the synergy of hydrophilic silica nanoparticles (N20) and surfactant Tween 80. The void interconnectivity and pore size of the hydrogels can be readily tailored by varying the concentrations of N20 nanoparticles and Tween 80. The in vitro release of the AAO-loaded hydrogels with different inner morphologies was evaluated and showed controlled release activity. The antibacterial activity of the AAO-loaded hydrogel was evaluated against Staphylococcus aureus and Escherichia coli. This kind of hydrogel exhibited excellent and long-term antibacterial activity indicating its potential use in biomedical and infection prevention applications.

Macroporous antibacterial hydrogels with tunable pore structures fabricated by using Pickering high internal phase emulsions as templates by Shengwen Zou, Zengjiang Wei, Yang Hu, Yonghong Deng, Zhen Tonga and Chaoyang Wang, Polym. Chem. 2014, 5, 4227-4234.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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