Static and dynamic light scattering by aqueous polyelectrolyte solutions: effect of molecular weight, charge density and added salt

Abstract Aqueous solutions of quaternized poly(2-vinylpyridine) were investigated by static (SLS) and dynamic (DLS) light scattering over a wide range of polyelectrolyte, c pe , and salt concentrations, c s (10 −3 ≤ c pe ≤ 10 2 gl −1 , 10 −5.5 ≤ c s ≤ 10 −1 moll −1 ). Using DLS the cooperative diffusion coefficient D was measured as a function of c pe and c s . D exhibits a characteristic behaviour in each of three different concentration regimes. In the ‘dilute lattice’ regime, where λ = c pe c s ⪡ 1 , one diffusion coefficient is observed. In the transition regime, where λ ≈ 1, D increases with increasing polyelectrolyte concentration and a slow diffusive mode gradually appears. For λ ⪢ 1…

Dissolution de polystyrene marque par de la fluorescence dans une matrice de masse moleculaire moyenne en poids de 110000

Book Review: Rubberlike Elasticity?A Molecular Primer. By J. E. Mark and B. Erman

Synthesis and properties of model - micronetworks

Microgels are small network particles with overall dimensions in the 100nm-region. Some experiments concerning the behaviour of cross-linked matter can be more easily performed using the molecular nature of μ-gels. In this publication, the synthesis and characterization by light and neutron scattering and dynamic-mechanical shear experiments of two different types of μ-gels are presented.

Diffusion of labeled macromolecules in molten polystyrenes studied by a holographic grating technique

Diffusion de polystyrene, de differentes masses moleculaires marque a la fluoresceine. Influence de la temperature

Entanglement in polystyrene detected by translational diffusion of photo-labeled molecules

Mesure des coefficients de diffusion de polystyrenes marques et comparaison avec une equation phenomenologique reliant la masse moleculaire critique entre les enchevetrements Mc a ces masses moleculaires respectives de la chaine diffusant et de la matrice. Comparaison avec les theories recentes

Diffusion coefficients D of singly and doubly end-labeled polystyrenes (PS) with molecular weights in the range 6500 ≤ M ≤ 75400 were measured in a PS matrix of molecular weight M′ = 111000, and in matrices with M′ = M. At 212°C, we find no influence of the label. In a power-law description D = D0 · M−α · M′−β we find α = 2,0 for M′ = 111000 and α + β = 2,4 for M = M′. The crossover to Rouse-like behavior for short-M chains is at Me ≈ 18000 for the former (high M′), and at Mc ≈ 33000 in the latter (M′ = M) case. At 185°C, we find a more complex scaling behavior and different D values for singly and doubly labeled PS.

Rubberlike elasticity?a molecular primer. ByJ. E. Mark andB. Erman. Wiley, Chichester 1988. viii, 196 pp., bound, � 23.70.?ISBN 0-471-61499-8

The Next 100 Years of Polymer Science

International audience; The year 2020 marks the 100th anniversary of the first article on poly merization, published by Hermann Staudinger. It is Staudinger who realized that polymers consist of long chains of covalently linked building blocks. Polymers have had a tremendous impact on the society ever since this initial publication. People live in a world that is almost impossible to imagine without synthetic polymers. But what does the future hold for polymer science? In this article, the editors and advisory board of Macromolecular Chemistry and Physics reflect on this question.

Telechelic α,ω-macrozwitterions — narrowly distributed polystyrene chains oppositely charged at each end — were synthesized via anionic polymerization using direct functionalization with the initiator and the termination agent. The resulting products were purified (zwitterion content ≥ 0,95) and characterized with gel permeation chromatography, viscometry, static and dynamic light scattering and small-angle neutron scattering. In unpolar solvents as toluene, the polymeric zwitterions form clusters with molecular weights depending on concentration. In the dilute case, the clusters are relatively small and consist of approximately 8 zwitterions. The structure of these clusters is discussed by…

Terminaison d'un polystyrene lineaire telechelique avec des anions aux deux extremites a l'aide d'un agent de terminaison bifonctionnel et une haute dilution

Non-conventional Fe3C-based nanostructures

Novel Fe3C-based nanostructures with an inner layered structure have been synthesized by a simple medium-temperature (T = 700 °C) process based on carbothermal reduction. In this process, the iron precursor reacts with a selected nitrogen rich carbon source (namely, 4,5-dicyanoimidazole) to form wrapped nano-sheets of Fe3C@C(N). The nanosheets are composed of 5 nm crystalline Fe3C nanoparticles, which are integrated into a nitrogen-doped carbon phase giving rise to the wrapped morphology. By variation of reaction parameters (such as initial concentration, temperature, reaction time), the typical accompanying side products of iron carbide such as metallic iron and amorphous carbon can be kep…