Blending block copolymer micelles in solution ; obstacles of blending

Amphiphilic block copolymers can assemble into a variety of structures on the nanoscale in selective solvent. The micelle blending protocol offers a simple unique route to reproducibly produce polymer nanostructures. Here we expand this blending protocol to a range of polymer micelle systems and self-assembly routes. We found by exploring a range of variables that the systems must be able to reach global equilibrium at some point for the blending protocol to be successful. Our results demonstrate the kinetics requirements, specifically core block glass transition temperature, Tg, and length of the block limiting the exchange rates, for the blending protocol which can then be applied to a wide range of polymer systems to access this simple protocol for polymer self-assembly

The analysis of solution self-assembled polymeric nanomaterials

\u3cp\u3eThere has been much interest in the construction of soft nanomaterials in solution due to a desire to emulate the exquisite structure and function of Nature's equivalents (e.g. enzymes, viruses, proteins and DNA). Nature's soft nanomaterials are capable of selectivity, precision and efficiency in areas such as information storage and replication, transportation and delivery, and synthesis and catalysis. To this end, the use of small molecules, amphiphiles, colloids, and polymers have been investigated for the development of advanced materials in myriad fields of biomedicine and synthetic chemistry. Two major challenges are faced in this area of research: the reproducible, scalable and precise synthesis of such constructs and the reliable, accurate and in-depth analysis of these materials. This tutorial review will focus on this second aspect and provide a guide for the characterisation and analysis of soft nanomaterials in solution using scattering and microscopic techniques. This journal is\u3c/p\u3

Elongation of telechelic ionomers under shear: a rheological and rheo-optical study

The behavior under shear of solutions of α,ω-lithium sulfonato polystyrene (α,ω-LiPSS100) in toluene has been investigated by rheo-optics and rheology. Shear-thickening is observed and related to a strong increase of birefringence and a pronounced and rapid alignment of the polymer chains toward the flow direction leading to an important elasticity of the fluids. The draw ratio of the polymer chains under shear has been estimated from the rheo-optical data. When the fraction of loops is taken into account, draw ratios on the order of 4 are calculated in the shear thickening regime

Complexation between a hydrophobically modified chitosan and cyclodextrin homodimers singly or doubly connected through their primary sides: effects of their molecular architecture on the polymer properties in solution

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Electrochemical characterization of viscoelastic solutions of supramolecular polymers in phosphonium-based ionic liquids

International audienceWe have combined electrochemical, rheological and light scattering measurements to investigate the viscoelastic character of solutions of (2,4-bis (2-ethylhexylureido) toluene) (EHUT) in toluene in the presence of two ionic liquids: (trihexyl(tetradecyl) phosphonium hexafluorophosphate “Cyphos 110”) and (tris(pentafluoroethyl) trifluorophosphate “aph4-cph12”) used to substantially increase the solution conductivity required for the electrochemical study.The heterogeneous rate constant k0 of the Fc/Fc+ redox couple, the diffusivity (DFc), and the equivalent capacitance values of the double layer were measured in the presence and in the absence of EHUT. For Cyphos 110, the viscosity of solutions increases in the presence of EHUT, but the diffusion current exhibited no fluctuations. By opposition, for aph4-cph12, strong fluctuations of the diffusion current allowed to assign a viscoelastic character to the solutions when EHUT is added.Rheological and light scattering measurements revealed that the two ionic liquids act as chain stoppers for EHUT supramolecular chains. However, aph4-cph12 maintains the viscoelastic character of the EHUT solution whereas Cyphos 110 destroys the supramolecular structure

Amphiphilic diblock copolymers with a moderately hydrophobic block: Toward dynamic micelles

cited By 40International audienceA study was conducted to propose a way of transforming a frozen system into a dynamic one by acting on the chemical structure of the amphiphilic block copolymer. The approach consisted of introduction of some hydrophilic units in the hydrophobic block to reduce the interfacial tension between the moderately hydrophobic block the hydrophilic block and the aqueous medium, promoting unimer exchange. The investigation on a P(nBA-stat-AA)-b-PAA block copolymer, which was a pure poly(acrylic acid) (PAA) hydrophilic block connected to a statistical copolymer of nBA and AA units forming the moderately hydrophobic block. The investigation also focused on controlled synthesis of the P(nBA50%-stat-AA50%)99-b-PAA98 block copolymer using atom transfer radical polymerization (ATRP). This emphasized the statistical distribution of the hydrophobic (nBA) and hydrophilic (AA) units in the P(nBA50%-stat-AA50%)99 first block

One and two dimensional self-assembly of comb-like amphiphilic copolyelectrolytes in aqueous solution

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Effect of Self-Assembly on Phase Separation of Di- and Triblock Copolymers Mixed with Homopolymers in Aqueous Solution

The influence of association of amphiphilic diblock (BA) or triblock (BAB) copolymers on phase separation in binary solutions with linear homopolymer has been investigated. The effect of the homopolymer chemistry was investigated by mixing hydrophobically end-capped poly­(ethylene oxide) (PEO) with PEO or dextran homopolymers. Diblock copolymers self-assembled into star-like polymeric micelles, while triblocks formed flower-like polymeric micelles that further associate with increasing polymer concentration through bridging. Phase diagrams were determined and compared with those of mixtures of dextran with PEO homopolymers. For diblock/dextran mixtures, self-assembling favored phase separation, but much less than expected from the increased molar mass due to self-assembly. For triblock/dextran mixtures, self-assembly favored phase separation much more strongly than for diblock copolymers and was induced principally by the gain in entropy due to the formation of bridges. Macroscopic phase separation was also observed when large PEO homopolymers were mixed with either diblock or triblock copolymers, but it occurred at much lower concentrations in the latter case. Incompatibility due to different chemistry is more important than different architecture as a driving force for phase separation for mixtures of homopolymers with diblock copolymers, whereas for mixtures with triblock copolymers the architecture is more important