Supramolecular polymer hydrogels induced by host-guest interactions with di-[cyclobis(paraquat-p-phenylene)] cross-linkers: from molecular complexation to viscoelastic properties

Supramolecular polymer networks have been designed on the basis of a -electron donor/acceptor complex: naphthalene (N)/cyclobis(paraquat-p-phenylene) (CBPQT4+=B). For this purpose, a copolymer of N,N-dimethylacrylamide P(DMA-N1), lightly decorated with 1 mol% of naphthalene pendant groups, has been studied in semi-dilute un-entangled solution in the presence of di-CBPQT4+ (BB) crosslinker type molecules. While calorimetric experiments demonstrate the quantitative binding between N and B groups up to 60 °C, the introduction of BB crosslinkers into the polymer solution gives rise to gel formation above the overlap concentration. From a comprehensive investigation of viscoelastic properties, performed at different concentrations, host/guest stoichiometric ratios and temperatures, the supramolecular hydrogels are shown to follow a Maxwellian behavior with a strong correlation of the plateau modulus and the relaxation time with the effective amount of interchain cross-linkers and their dissociation dynamics, respectively. The calculation of the dissociation rate constant of the supramolecular complex, by extrapolation of the relaxation time of the network back to the beginning of the gel regime, is discussed in the framework of theoretical and experimental works on associating polymers

An easy and economically viable route for the decoration of carbon nanotubes by magnetite nanoparticles, and their orientation in a magnetic field

peer reviewedA simple, cheap and tunable approach for the decoration of carbon nanotubes by magnetite nanoparticles and their orientation in a magnetic field is reported.Eurocores program, SON

Controlled Radical Polymerization of Vinyl Acetate Mediated by a Bis(imino)pyridine Vanadium Complex

Source type: Prin

A triple carboxylic acid-functionalized RAFT agent platform for the elaboration of well-defined telechelic 3-arm star PDMAc

This communication describes the synthesis of a triple acid-functionalized RAFT agent and its use to prepare well-defined 3-arm star polymers of N,N-dimethylacrylamide (DMAc). A simple esterification reaction allowed the convenient integration of three electron-rich naphthalene recognition units on the RAFT agent platform and subsequently the elaboration of a naphthalene end-decorated telechelic 3-arm star PDMAc. This functionalized star polymer was further exploited to build a hydrogel with a complementary homoditopic host unit featuring tetracationic macrocycle cyclobis(paraquat-p-phenylene) units

RAFT polymerization of hydroxy-functional methacrylic monomers under heterogeneous conditions: effect of varying the core-forming block

Statistical copolymerization of a 1 : 1 molar ratio of a water-miscible monomer (2-hydroxyethyl methacrylate, HEMA) with a water-immiscible monomer (4-hydroxybutyl methacrylate, HBMA) has been conducted in water via reversible addition–fragmentation chain transfer (RAFT) polymerization using a water-soluble poly(glycerol monomethacrylate) macromolecular chain transfer agent (PGMA macro- CTA). In principle, such a hybrid formulation might be expected to be intermediate between RAFT dispersion polymerization and RAFT emulsion polymerization. Under such circumstances, it is of particular interest to examine whether both monomers are actually consumed and, if so, whether their rates of reaction are comparable. Given the water-solubility of both the PGMA macro-CTA and the free radical azo initiator, it is perhaps counter-intuitive that the water-immiscible HBMA is initially consumed significantly faster than the water-miscible HEMA, as judged by 1H NMR studies of this copolymerization. However, both comonomers are eventually almost fully consumed at 70 �C. A detailed phase diagram has been constructed for this RAFT formulation that enables reproducible syntheses of various pure copolymer morphologies, including spheres, worms and vesicles. It is emphasized that utilizing a 1 : 1 HEMA/HBMA molar ratio produces a core-forming statistical copolymer block that is isomeric with the poly(2-hydroxypropyl methacrylate) (PHPMA) core-forming block previously synthesized via RAFT aqueous dispersion polymerization (see A. Blanazs et al., Macromolecules, 2012, 45, 5099–5107). Hence it is rather remarkable that the thermo-responsive behavior of PGMA–P(HBMA-stat-HEMA) statistical block copolymer worm gels differs qualitatively from that exhibited by PGMA–PHPMA diblock copolymer worm gels

Al(OPri)3-catalysed halogen exchange processes of relevance to atom transfer radical polymerization: the effect depends on the metal electronic structure

International audienceWhether or not tri(isopropoxo)aluminium catalyses halogen exchange for an ATRP catalyst depends on the number of valence electrons

Etudes de processus de polymérisation radicalaire contrôlée par des complexes de molybdène

Des complexes organométalliques et de coordination à base de molybdène (Mo) ont été étudiés en polymérisation radicalaire contrôlée. Ce travail a permis de montrer qu'une nouvelle famille de complexes du type CpMoX2L2 (avec L2 = R2-diazadiène et X = Cl, I) est active en polymérisation radicalaire contrôlée du styrène et des acrylates. Une étude sur le mode d'action d'un cocatalyseur (Al(OiPr)3) est présentée. Une nouvelle voie de synthèse des précurseurs des complexes de coordination de Mo(IV) et de Mo(III) a été développée. L'utilisation de complexes simples de coordination en polymérisation radicalaire contrôlée du styrène est décrite. Une étude mécanistique a montré que le processus de propagation du radical actif sous des conditions d'ATRP doit être similaire à celui d'une polymérisation radicalaire classique. Une étude sur des complexes de Mo(II) a permis, entre autres, de montrer qu'un catalyseur cationique de CpMo(II) peut également contrôlée la polymérisation de l'acrylate de méthyle.Organometallic and coordination complexes of molybdenum (Mo) have been studied in controlled radical polymerisation. A new tunable family of CpMoX2L2 complexes (L2 = R2-diazadiene; X = Cl, I) active in ATRP has been introduced. The ATRP method with organometallic Mo complexes has been extended successfully to acrylate monomers and to a PMA-b-PS block copolymer. A reasonable hypothesis for the role of Al(OiPr)3 on the ATRP rate has been formulated. A relationship between electronic structure and Al(OiPr)3 catalysis for the halogen exchange between ATRP catalyst and initiator has been dicovered. New and simpler syntheses of the commonly used MoCl4(Et2O)2 and MoCl3(THF)3 starting materials have been optimized. Simple (non organometallic) coordination compouds of Mo(III) are effective for the ATRP of styrene. New organometallic compounds of Mo(II) containing a diazadiene ligand have been synthesized; complex CpMo(CO)2(iPr2-dad)+,I- is capable of controlling the radical polymerisation of methyl acrylate.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Combination of ring-opening polymerization and "click" chemistry towards functionalization of aliphatic polyesters

Azide pendent groups of aliphatic polyesters have been derivatized into tertiary amines, ammonium salts and poly(ethylene oxide) grafts. The experimental conditions have been optimized (organic solvent, 35 degrees C), such that the aliphatic polyesters are not degraded, including even poly(lactide) which is very sensitive to attack by weak nucleophiles