Archive for the ‘Paper of the Week’ Category

Paper of the week: Patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures

Palacios-Cuesta et al. describe the patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures.

Microorganisms have a remarkable ability to adhere to virtually any type of abiotic surface, proliferate and subsequently form biofilms.  Since materials may need to interact differently with microorganisms, the adherent or repellent properties of materials towards bacteria are an extremely important consideration in their design. For example, materials used as implants need to remain free from contamination, in order to reduce device-associated infections, and hence, antifouling surfaces are prepared using water repellent polymers or by anchoring antimicrobial compounds. Conversely, surfaces capable of controlled immobilization and removal of microorganisms have been equally explored for a rather broad range of applications, including sophisticated systems such as biosensors or biomolecular motors. Thus far, precise immobilisation of microorganisms, and in particular bacteria, onto surfaces has been achieved by using a range of different fabrication approaches. However, there are relatively few examples of controlled immobilisation of single bacteria that don’t involve expensive approaches or time-consuming multistep procedures.

In this paper, Palacios-Cuesta and colleagues describe the development of different surface patterns using a photolithographic-based technique that does not require the use of high resolution masks or clean rooms and produces surface patterns with micrometer and submicrometer resolution. The procedure is based on the cross-linking and degradation processes occurring in polystyrene upon exposure to UV light. Together, these processes produce different patterns depending, not only on the mask, but also on the experimental conditions employed. With this approach it is possible to produce patterns with nanoscale resolution without expensive fine focalisation settings. Of particular interest, the authors demonstrate the feasibility of this strategy to incorporate functional groups to modulate the affinity between the bacteria and the surface. In particular, hydrophilic segments, i.e. poly(acrylic acid) that favour bacterial immobilisation are introduced. The strategy employed allows not only the incorporation of functional groups, but also enables the fine tuning of the amount of hydrophilic functional groups. This unique feature is used by the authors to determine the role of surface hydrophilicity on the adhesion of Staphylococcus aureus onto the different surface patterns. Finally, those surfaces on which both photodegradation and photo-cross-linking occur produce thin patterns largely below the micrometer that are then used to prepare arrays of isolated S. aureus bacteria. The formation of bacterial arrays of S. aureus on the single-cell level has been a challenge since they exhibit a large tendency to grow in clusters. This technology is exciting given its potential for enabling the isolation of single bacteria for diagnosis, and the study of bacterial populations at the single cell level.

Patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures by Marta Palacios-Cuesta, Aitziber L. Cortajarena, Olga García and Juan Rodríguez-Hernández, Polym. Chem., 2015, 6, 2677-2684.

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: Nucleobase-functionalized acrylic ABA triblock copolymers and supramolecular blends

Long et al describe the synthesis of nucleobase-functionalized acrylic triblock copolymers.

Reversible addition-fragmentation chain transfer (RAFT) polymerization afforded the unprecedented synthesis of well-defined acrylic ABA triblock copolymers with nucleobase-functionalized external blocks and a central poly(n-butyl acrylate) (PnBA) block. Size exclusion chromatography (SEC) confirmed the molecular weight and molecular weight distribution of the central block. 1H NMR spectroscopy revealed the successful chain extension of the PnBA macro-chain transfer agent (CTA) using adenine or thymine-functionalized acrylic monomers. The acrylic monomer with a flexible spacer to the pendant nucleobases promoted intermolecular recognition of nucleobases and long range segmental motion of polymer main chains. The external block glass transition temperatures (Tg’s) of thymine (T) and adenine (A) functionalized blocks were 52 °C and 76 °C, respectively. Thermomechanical and morphological analysis revealed the effect of processing conditions on self-assembly and microphase-separated morphology of nucleobase-functionalized ABA copolymers. Thymine and adenine-functionalized ABA triblocks formed a thermodynamically stable, hydrogen-bonded complex upon blending. The supramolecular blend exhibited a cylindrical microphase-separated morphology with an extended plateau window compared to the individual block copolymers. The complementary hydrogen bonding between adenine and thymine formed a thermally labile, physically crosslinked, network that exhibited enhanced mechanical performance with melt processability. Thus, these ABA nucleobase-functionalized block copolymers demonstrate potential as thermoplastic elastomers for hot melt adhesives and coatings.

Nucleobase-functionalized acrylic ABA triblock copolymers and supramolecular blends by Keren Zhang, Motohiro Aiba, Gregory B. Fahs, Amanda G. Hudson, William D. Chiang, Robert B. Moore, Mitsuru Ueda and Timothy E. Long Polym. Chem., 2015,6, 2434-2444

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: Renewable, fluorescent, and thermoresponsive cellulose copolymers

Hufendiek et al. report the preparation of renewable, fluorescent, and thermoresponsive cellulose copolymers via light-induced ligation in solution copolymers.


Hufendiek et al. introduce a mild photochemically driven strategy for the synthesis of fluorescent cellulose copolymers using filter paper as the starting material. Thermoresponsive behaviour in water is imparted to the brush-like structures by grafting of poly(N-isopropylacrylamide) side chains. All reactions take place in homogenous solutions, allowing the design of novel advanced materials from renewable resources.

Renewable, fluorescent, and thermoresponsive: cellulose copolymers via light-induced ligation in solution by Andrea Hufendiek, Christopher Barner-Kowollik and Michael A. R. Meier, Polym. Chem., 2015, 6, 2188-2191

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: Nanoscale detection of metal-labeled copolymers in patchy polymersomes

Ruiz-Pérez et al. report the nanoscale detection of metal-labelled copolymers in patchy polymersomes.

The synthesis of polymersome-forming block copolymers using two different synthetic routes based on Atom Transfer Radical Polymerisation (ATRP) and Reversible Addition Fragmentation chain Transfer (RAFT) polymerisation is reported. Functionalisation with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) allowed the block copolymer chains to be labelled with electron-dense metal ions (e.g. indium). The resulting metal-conjugated copolymers can be visualised by transmission electron microscopy with single chain resolution, hence enabling the study of polymer/polymer immiscibility and phase separation on the nano-scale.

Nanoscale detection of metal-labeled copolymers in patchy polymersomes by Lorena Ruiz-Pérez, Jeppe Madsen, Efrosyni Themistou, Jens Gaitzsch, Léa Messager, Steven P. Armes and Giuseppe Battaglia, Polym. Chem., 2015, 6, 2065-2068.

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: Titin-mimicking polycyclic polymers with shape regeneration and healing properties

Schuetz et al. describe polycyclic polymers with shape regeneration and healing properties.

Polycyclic polymers based on cyclic (ABC)n-multiblock-copolymers are formed via stepwise polymerization of three individual blocks and exploiting the ring merging reaction of these ring polymers. The so-obtained precursor ring-polymers were interconnected via click reaction. Small blocks within the rings with the ability to form self-complementary hydrogen bonds lead to intra- and intermolecular links between polycyclic polymers. The obtained materials, which mimic nature’s paragon Titin, have some extraordinary material properties concerning elasticity and energy dissipation.

Titin-mimicking polycyclic polymers with shape regeneration and healing properties by Jan-Hendrik Schuetz, Peng Wentao and Philipp Vana, Polym. Chem., 2015,6, 1714-1726.

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: A fast track strategy toward highly functionalized dendrimers with different structural layers

Sharma et al. describe a fast track strategy toward highly functionalized dendrimers with different structural layers: an “onion peel approach”

An accelerated strategy depending on different chemical building blocks between each layer, coined “onion peel”, was used to construct a library of third generation dendrimers with 108, 180 and 252 hydroxyl surface groups using a combination of microwave assisted highly efficient CuAAC and thiol–ene reactions. These dendrimers were conveniently acquired with high purity and good yields in a divergent manner using a variety of orthogonal and dense AB3, AB5, and AB7building blocks. The resulting polyhydroxylated dendrimers tested in several human cell types did not impair mitochondrial metabolic function or cell viability suggesting that they are good candidates for applications in biological investigations.

A fast track strategy toward highly functionalized dendrimers with different structural layers: an “onion peel approach” by Rishi Sharma, Issan Zhang, Leïla Abbassi, Rabindra Rej, Dusica Maysinger and René Roy, Polym. Chem., 2015, 6, 1436-1444.

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: Dynamic intracellular delivery of antibiotics via pH-responsive polymersomes

Lane et al. report the intracellular delivery of antibiotics via pH-responsive polymersomes.

Reversible addition-fragmentation chain transfer (RAFT) polymerisation was employed to prepare a series of copolymers consisting of 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methyl ether methacrylate (FWavg [similar] 950 Da) (O950) with variable comonomer compositions and molecular weights for use as polymeric scaffolds. Reactivity ratios for the monomer pair were determined to be 1.37 and 0.290 respectively. To these scaffolds, trithiocarbonate-based RAFT chain transfer agents (CTAs) were grafted using carbodiimide chemistry. The resultant graft chain transfer agents (gCTA) were subsequently employed to polymerise dimethylaminoethyl methacrylate (DMAEMA) and N-(2-hydroxypropyl)methacrylamide (HPMA) between degrees of polymerisation (DP) of 25 and 200. Kinetic analysis for the polymerisation of DMAEMA targeting a DP of 100 from a 34 arm graft gCTA show linear Mn conversion and pseudo first order rate plots with narrow molecular weight distributions that move toward lower elution volumes with monomer conversion. Đ values for these polymerisations remain low at around 1.20 at monomer conversions as high as 70%. pH-responsive endosomalytic brushes capable of spontaneously self-assembling into polymersomes were synthesised and a combination of dynamic light scattering (DLS), cryoTEM, and red blood cell haemolysis were employed to evaluate the aqueous solution properties of the polymeric brush as a function of pH. Successful encapsulation of ceftazidime and pH-dependent drug release properties were confirmed by HPLC. Intracellular antibiotic activity of the drug-loaded polymersomes was confirmed in a macrophage coculture model of infection with Burkholderia thailandensis and RAW 264.7 cells.

Dynamic intracellular delivery of antibiotics via pH-responsive polymersomes by D. D. Lane, F. Y. Su, D. Y. Chiu, S. Srinivasan, J. T. Wilson, D. M. Ratner, P. S. Stayton and A. J. Convertine, Polym. Chem., 2015,6, 1255-1266.

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: Efficient microencapsulation of a liquid isocyanate with in situ shell functionalization

Nguyen et al. outline the efficient microencapsulation of a liquid isocyanate with in situ shell functionalization.

Nguyen et al. report on a one-pot, facile approach for the encapsulation of the liquid hexamethylene diisocyanate isocyanurate trimer in polyurea microcapsules formed via the oil-in-water interfacial reaction of an uretonimine-modified diphenyl methane diisocyanate trimer with triaminopyrimidine; with in situ shell functionalization/modification using different types of hydrophobic agents. Remarkably, the use of hexamethylenedisilazane resulted in microcapsules of about 70 μm in diameter, with a smooth outer surface and a high isocyanate core content up to 85 wt% as determined by quantitative online FT-IR analysis of the extracted core. On the other hand, the use of an alkylamine, fluorinated aromatic amine and/or perfluoride amine provided microcapsules of approximately 100 to 150 μm in diameter containing around 65–75 wt% of the isocyanate core content, with the outer shell surface bearing pendant hydrophobic groups as confirmed by SEM-EDX. The effects of the functionalizing compound on the microcapsule properties such as shell morphology, size distribution and stability were assessed. After one day immersion in water, the initial isocyanate content of the microcapsules with a non-functionalized shell dropped rapidly from 49 to 15 wt%, whereas the ones with the modified shell structure maintained their core content, suggesting a significantly enhanced microcapsule stability.

Efficient microencapsulation of a liquid isocyanate with in situ shell functionalization by Le-Thu T. Nguyen, Xander K. D. Hillewaere, Roberto F. A. Teixeira, Otto van den Berg and Filip E. Du Prez, Polym. Chem., 2015, 6, 1159-1170.

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: Highly regioselective Pd/C-catalyzed direct arylation toward thiophene-based π-conjugated polymers

Hayashi et al. have successfully developed a highly regioselective Pd/C-catalysed direct arylation toward thiophene-based π-conjugated polymers.

Pd/C heterogeneous catalysts were used in the direct arylation polycondensation of thiophenes. The efficient and highly regioselective polycondensation of thiophene monomers was achieved under phosphine-free conditions to give linear π-conjugated alternating copolymers with high molecular weight in high yield.

Highly regioselective Pd/C-catalyzed direct arylation toward thiophene-based π-conjugated polymers by Shotaro Hayashi, Yoshihisa Kojima and Toshio Koizumi Polym. Chem., 2015,6, 881-885.

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: Novel polymer synthesis methodologies using combinations of thermally- and photochemically-induced nitroxide mediated polymerization

Guillaneuf and Gigmes and co-workers discuss novel polymer synthesis methodologies using combinations of thermally- and photochemically-induced nitroxide mediated polymerization

The combination of thermally- and photochemically-induced polymerization using light-sensitive alkoxyamines was investigated. The thermally driven polymerizations were performed via the cleavage of the alkoxyamine functionality, whereas the photochemically-induced polymerizations were carried out either by nitroxide mediated photo-polymerization (NMP2) or by a classical type II mechanism, depending on the structure of the light-sensitive alkoxyamine employed. Once the potential of the various structures as initiators of thermally- and photo-induced polymerizations was established, their use in combination for block copolymer syntheses was investigated. With each alkoxyamine investigated, block copolymers were successfully obtained and the system was applied to the post-modification of polymer coatings for application in patterning and photografting.

Novel polymer synthesis methodologies using combinations of thermally- and photochemically-induced nitroxide mediated polymerization by Jason Morris, Sofia Telitel, Kathryn E. Fairfull-Smith, Steven E. Bottle, Jacques Lalevée, Jean-Louis Clément, Yohann Guillaneuf and Didier Gigmes Polym. Chem., 2015,6, 754-763

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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