Archive for the ‘Paper of the Week’ Category

Paper of the week: Pristine and thermally rearranged gas separation membranes

Pinnau et al present the pristine and thermally rearranged gas separation membranes.

A novel o-hydroxyl-functionalized spirobifluorene-based diamine monomer, 2,2′-dihydroxyl-9,9′-spirobifluorene-3,3′-diamine (HSBF), was successfully prepared by a universal synthetic method. Two o-hydroxyl-containing polyimides, denoted as 6FDA-HSBF and SPDA-HSBF, were synthesized and characterized. The BET surface areas of 6FDA-HSBF and SPDA-HSBF are 70 and 464 m2 g−1, respectively. To date, SPDA-HSBF exhibits the highest CO2 permeability (568 Barrer) among all hydroxyl-containing polyimides. The HSBF-based polyimides exhibited higher CO2/CH4 selectivity than their spirobifluorene (SBF) analogues (42 for 6FDA-HSBF vs. 27 for 6FDA-SBF) due to an increase in their diffusivity selectivity. Polybenzoxazole (PBO) membranes obtained from HSBF-based polyimide precursors by thermal rearrangement showed enhanced permeability but at the cost of significantly decreased selectivity.

Pristine and thermally-rearranged gas separation membranes from novel o-hydroxyl-functionalized spirobifluorene-based polyimides by Xiaohua Ma, Octavio Salinas, Eric Litwiller and Ingo Pinnau* Polym. Chem., 2014,5, 6914-6922.

DOI: 10.1039/C4PY01221F

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: Oximes as reversible links in polymer chemistry

Sumerlin et al presented the preparation of dynamic star shaped polymers using oximes as reversible links.


Summerlin and his co-workers have demonstrated the formation of oxime-functional macromolecular stars that are able to dissociate and reconstruct themselves upon application of a stimulus. The reversible nature of the oxime bond in the presence of externally added alkoxyamines or carbonyl compounds enables reconfiguration via competitive exchange. Reversible addition–fragmentation chain transfer (RAFT) polymerization was utilized to prepare well-defined amphiphilic block copolymers in which a hydrophobic keto-functional block allowed self-assembly into micelles in water. Adding a difunctional alkoxyamine small molecule to these solutions resulted in crosslinking of the micelles to yield macromolecular stars. The reversible nature of the O-alkyl oxime linkages was demonstrated via competitive exchange with excess of carbonyl compounds or monofunctional alkoxyamine under acidic conditions and at elevated temperatures to result in dissociation of the stars to unimolecular oxime-functional polymer chains.

Oximes as reversible links in polymer chemistry: dynamic macromolecular stars by Soma Mukherjee, Abhijeet P. Bapat, Megan R. Hill and  Brent S. Sumerlin Polym. Chem., 2014,5, 6923-6931.

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: Fluorescent PEGylation agent by a thiolactone-based one-pot reaction

One pot preparation of fluorescent PEGylated proteins by a thiolactone reaction to be used in theranostic applications has been reported by Tao et al.

Theranostic combinations usually contain an imaging, a therapeutic and a cloaking component to simultaneously fulfil diagnostic and therapeutic functions. Using upgraded PEGylation technology, a straightforward one-pot strategy based on thiolactone ring-opening has been developed to facilely synthesize a multifunctional PEGylation agent, fluorescent protein-reactive poly(ethylene glycol) (PEG), which can subsequently react with a model therapeutic protein to form a fluorescent PEGylated protein as a model of sophisticated theranostic combinations.

Fluorescent PEGylation agent by a thiolactone-based one-pot reaction: a new strategy for theranostic combinations by Yuan Zhao, Bin Yang, Yaling Zhang, Shiqi Wang, Changkui Fu, Yen Wei and   Lei Tao Polym. Chem., 2014,5, 6656-6661

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: 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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