Polymer Chemistry Blog

Facile synthetic and modification procedures of functionalized polymers have been the subject of extensive fundamental and applied research efforts during the last decade. The concept of ‘click’ chemistry induced a transition towards ‘on-demand’ preparation of tailored polymeric systems. The toolbox of research labs is currently loaded with a variety of established ‘click’ reactions, offering ample possibilities for macromolecular design and synthesis. Moreover, the development and valorization of novel polymer materials with a broad range of applications (medicines, electronics, bioconjugation, labeling, etc.) significantly promoted interdisciplinary research. The elaboration of innovative procedures and the combination of existing reactions in multi-step one-pot sequences further exemplify the scientific eagerness to study the possibilities and limitations of ‘click’ chemistry to the full extent.

Filip Du Prez et al. have elaborated a straightforward, isocyanate-free method for the synthesis of functionalized polyurethanes, based on amine–thiol–ene conjugation. Aminolysis of a readily available AB′-urethane monomer, containing both an acrylate (A) and a thiolactone unit (B′), facilitates the preparation of various reactive thiol–acrylates. In situ polymerization via Michael addition proceeds under ambient conditions, yielding polyurethanes with a large variety of chemical functionalities. Side-chain functionality originates from the modular use of different amines, allowing for the introduction of pendent functional groups (e.g. double bond, triple bond, furfuryl, tertiary amine, morpholine) along the polyurethane backbone. Extensive model studies revealed the kinetic profile of this reaction sequence and excluded the occurrence of competing reactions, such as aza-Michael addition and disulfide formation. This mild one-pot reaction requires no additives or external trigger and the obtained polyurethanes remain soluble throughout the process, enabling post-polymerization modification in the same reaction medium.

One-pot, additive-free preparation of functionalized polyurethanes viaamine–thiol–ene conjugation by Pieter Espeel, Fabienne Goethals. Frank Driessen, Le-Thu T. Nguyen and Filip Du Prez, Polym. Chem. 2013, 4, 2449-2456.

Conjugated aromatic polymers have attracted great attention since 1970s. Myriad of studies have been reported on five-membered heterocycles containing polymers such as polypyrroles, polythiophenes and their derivatives due to their susceptible electronic and optical properties. Recent studies showed that furan containing polymers have some priorities over thiophene based ones for the application of polymer organics in advanced technological applications. For instance, the greater electron withdrawing ability of furan is capable of reducing the HOMO energy level of the D parts in the solar cells, which results in the high open circuit voltage.

Cihaner, Onal and their coworkers have designed and synthesized two new furan and benzochalcogenodiazole based monomers, namely 4,7-di(furan-2-yl)benzo[c][1,2,5]-selenadiazole (FSeF) and 4,7-di(furan-2-yl)benzo[c][1,2,5]thiadiazole (FSF), via a donor–acceptor–donor approach. The monomers were electrochemically polymerized via potentiodynamic or potentiostatic methods. The monomers and their polymers exhibited lower oxidation potentials (1.16 V and 1.06 V for monomers; 0.93 V and 0.80 V for polymers vs. Ag/AgCl) and red shifts of the whole dual-band absorption spectra upon moving from S to Se. Intramolecular charge transfer properties of the monomers and the polymers were demonstrated by using electroanalytical and optical methods. Also, the polymers PFSeF and PFSF were multicolored at different redox states and have low band gaps of 1.43 eV and 1.61 eV, respectively.

Furan and benzochalcogenodiazole based multichromic polymers via a donor–acceptor approach by Merve İçli-Özkut, Halil İpek, Baris Karabay, Atilla Cihaner and Ahmet M. Önal Polym. Chem., 2013, 4, 2457-2463

In this context, by combining atom-transfer radical polymerization (ATRP) with thiol–epoxy‘click’ chemistry, Khan and co-workers described a general and effient synthetic scheme, free from the usual protection/deprotection requirement of organic synthesis, for installation of two different types of functional groups at a polymer chainend. This strategy also allowed for total control over the number of the chain-end functionalities. In essence, the present strategy established a novel, modular and efficient route to chain-end multifunctional polymers with chemically complex yet molecularly precise structures and is expected to impact the current design of functional soft materials targeted for sophisticated applications.

Protecting-group-free synthesis of chain-end multifunctional polymers by combining ATRP with thiol–epoxy ‘click’ chemistry by Ikhlas Gadwal and Anzar Khan, Polym. Chem., 2013, 4, 2440-2444.

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

In this communication, Yuan and co-workers prepared mesoporous polyelectrolyte networks through the ionic complexation between imidazolium-based cationic PILs and organic oligoacids in ammonia-containing diethyl ether. The as-synthesized porous networks exhibited good structural stability and large specific surface area up to 290 m² g^-1. This unique template-free strategy is very simple in operation and was shown to be generally valid for a variety of multivalent carboxylic acids, including many natural acid molecules. Interestingly, the performance of porous networks in dye removal from ethanol was demonstrated to be superior to activated carbon and mesoporous silica.

Organic acids can crosslink poly(ionic liquid)s into mesoporous polyelectrolyte complexes by Qiang Zhao, Sebastian Soll, Markus Antonietti and Jiayin Yuan, Polym. Chem., 2013, 4, 2432-2435.

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

Nanofibrous scaffolds possessing mechanical properties, porous microstructure, and dimensional similarity to collagen fibers have been used to mimic the natural extracellular matrix (ECM) and are highly relevant for tissue engineering in a number of different applications. Polymeric nanofibers have been fabricated into a variety of constructs and scaffolds using melt- or electrospinning processes. For regenerative medicine applications, the polymeric precursors used to fabricate the nanofiber-based scaffolds should be both biocompatible and biodegradable. Many biodegradable and biocompatible polymers have been widely investigated as fiber and nanofiber precursor materials. Although these degradable polymers meet several of the basic requirements for tissue engineering applications, bioactive molecules to guide cellular behavior and preserve cell phenotype are required for optimal performance.

In this context,  Becker and co-workers described a polymerization method utilizing 4-dibenzocyclooctynol (DIBO) as an initiator for the ring-opening polymerization of 3-caprolactone which yielded an end-functionalized PCL polymer. The DIBO group survived the relatively mild polymerization conditions and offered efficient, orthogonal and biocompatible functionalization opportunities for both the polymer and polymer-derivatized biomaterials. The combination of PCL and DIBO enabled large-scale production of a new type of easily functionalizable nanofiber-based scaffold with versatile regenerative medicine applications.

4-Dibenzocyclooctynol (DIBO) as an initiator for poly(ε-caprolactone): copper-free clickable polymer and nanofiber-based scaffolds by Laurent Chabanne, Stefan Pfirrmann, David J. Lunn and Ian Manners, Polym. Chem., 2013, 4, 2215-2218.

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