Archive for November, 2012

Paper of the week: Single chain polymeric nanoparticles as compartmentalised sensors

The unique physical properties of supramolecular polymers resulted in a myriad of potential applications ranging from electronics to healthcare and high performance materials. The large spectrum of available self-assembling molecules allows the properties of supramolecular polymers to be tuned to specific requirements of the desired applications. It has been recently shown that linear polymers grafted with non-covalent (or dynamic covalent) interacting groups lead, under selected conditions, to the folding of single polymeric chains into what are now termed single chain polymeric nanoparticles (SCPNs). Due to the unique properties of SCPNs, these well-defined nanometer-sized objects are actively investigated for use in advanced applications in low viscosity coatings, catalytic systems and nanomedicine.

Graphical abstract: Single chain polymeric nanoparticles as compartmentalised sensors for metal ions

In this context, Palmans and co-workers envisionned chemosensing of metal ions as an interesting application of SCPNs. The authors prepared 3,3′-bis(acylamino)-2,2′-bipyridine substituted benzene-1,3,5-tricarboxamide (BiPy-BTA) grafted polynorbornene polymers. The polymers fold intramolecularly via pp interactions into fluorescent, compartmentalised particles of nanometer-size. Spectroscopic and light scattering techniques show that the compact conformation of the folded polymer is affected by increasing the BiPy-BTA functionalisation degree and by changing the solvent polarity. Changes in the conformation are accompanied by changes in the fluorescence intensity. Due to the affinity of the BiPy units for metal ions such as copper, the particles obtained are effective sensors for these metals. The compartmentalisation of the binding motifs in SCPNs proves to be advantageous in sensor applications of these particles.

Single chain polymeric nanoparticles as compartmentalised sensors for metal ions by Martijn A. J. Gillissen, Ilja K. Voets, E. W. Meijer and Anja. R. A. Palmans, Polym. Chem., 2012, 3, 3166-3174.

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Author of the Week: Dr. Olivier Coulembier

Dr. Olivier Coulembier received his PhD degree from University of Mons-Hainaut (Belgium) in 2005 and joined Professor Robert M. Waymouth at the University of Stanford (United States) for his postdoctoral research in 2006.  He is currently a Research Associate by Belgian F.N.R.S. in the Laboratory of Polymeric and Composite Materials (LPCM) of Professor Philippe Dubois at University of Mons.  The objective of his research is devoted to the application of different polymerization techniques to generate original polymer materials of various topologies and issued from the macromolecular engineering fine-tuning. He has (co-)authored 62 scientific papers in international journals, 2 patents and 2 book chapters. Website: http://morris.umh.ac.be/smpc/

What was your inspiration in becoming a chemist?

Quite honestly, I didn’t fall into chemistry by real passion, I was just not really sure to fix my choice since all sciences disciplines were very interesting to me. I didn’t realize the importance of chemistry until my third year at University where polymer chemistry really peaked my interest and fed my passion. Polymer chemistry is for me the most interesting scientific field since it allows playing and creating small molecules but also fine-tune their association into simple to complex macromolecular structures and of course use a plethora of techniques to characterize them.

What was the motivation to write your Polymer Chemistry article?

In my young career, I spent almost 90% of my time to control the preparation of original polyester structures. Quite recently, by developing metal-free catalytic systems, we were able to prepare pure cyclic polyesters which proved their interest in the field by showing up physical properties different than their linear homologues.  Because people in my group are also preparing polyelectroconjugate structures, I simply wanted to merge those two activities.

Why did you choose Polymer Chemistry to publish your work? (DOI:10.1039/C2PY20647A)

Polymer Chemistry is an excellent and very promising European polymer journal. Importantly, the review process is very fast and serious.

How do you spend your spare times?

With my wife and my two daughters, of course, but also in the gym.

Which profession would you choose if you were not a scientist?

Younger, I was dreaming becoming a professional basketball player …

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Paper of the week: Role of multitopicity in hydrogen bonded supramolecular polymers

Hydrogen bonding interactions in aqueous media are often very weak because of the competition from water molecules, but they can still have a decisive effect on self-assemblies when used in combination with other interactions. In the case of amphiphiles with a hydrophobic part made from flexible alkyl chains, the introduction of hydrogen bonds within the hydrophobic domains through urea groups has been shown to dramatically increase the viscosity of aqueous solutions, and to enable self-sorting between amphiphiles of distinct structures. Another popular approach to synthesise viscous solutions or gels consists in decorating water soluble high molar mass polymers with hydrophobic groups.

Graphical abstract: Hydrogen bonded supramolecular polymers in protic solvents: role of multitopicity

In this article, Bouteiller and co-workers investigated the properties of systems combining both design elements, i.e. macromolecules with hydrophobic groups able to form very long anisotropic hydrophobic domains. A strong influence of both the number of associative groups per chain and the polydispersity has been demonstrated. In water, where the interactions between stickers are strong, the monomer self-assembles into filaments, but all other compounds with more than one sticker per chain are insoluble. In methanol, where the interactions between stickers are weaker, neither the monomer nor the monodispersed dimer is assembled, whereas polydispersed chains with an average number of stickers per chain of 2 or 3 self-assemble into filaments, leading to macroscopic gelation.

Hydrogen bonded supramolecular polymers in protic solvents: role of multitopicity by Marion Tharcis, Thomas Breiner, Joël Belleney, François Boué and Laurent Bouteiller, Polym. Chem., 2012, 3, 3093-3099.

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Paper of the week: Fluorescence resonance energy transfer in recognition-mediated polymer-quantum dot assemblies

Graphical abstract: Fluorescence resonance energy transfer in recognition-mediated polymer-quantum dot assemblies

Organization of nanoparticles (NPs) into morphologically controlled and organised structures is a central issue for bottom-up fabrication of functional devices in optoelectronics, sensing, catalysis and medicine. Directed host–guest assembly of NPs into polymer matrices is an effective route to form structured NP assemblies with advantageous optical, electronic, magnetic, and mechanical properties. In this article, Cooke, Rotello and co-workers reported recognition mediated assembly of ZnSe quantum dots (QDs) with a chromophore-functionalized polymer, facilitating fluorescence resonance energy transfer (FRET) from QDs to the chromophore. The authors designed and synthesized a polyfunctional copolymer featuring a solubilising methyl methacrylate (MMA) element, a diamidopyridine (DAP) recognition element and a flavin (Fl) chromophore. Thymine functionalized ZnSe QDs (Thy-QDs) were used as the guest in the assembly. Due to the spectral overlap and close proximity of the QDs and flavin units in the assembly, FRET was observed from QDs to flavin. This methodology of producing self-assembled structures both in solution and solid state provides a powerful tool for the creation of highly structured multifunctional materials and devices.

Fluorescence resonance energy transfer in recognition-mediated polymer-quantum dot assemblies by Vikas Nandwana, Brian Fitzpatrick, Qian Liu, Kyril M. Solntsev, Xi Yu, Gülen Yesilbag Tonga, Serkan Eymur, Murat Tonga, Graeme Cooke and Vincent M. Rotello, Polym. Chem. 2012, 3, 3072-3076.

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