No abstract

Neutron coherent scattering techniques have been used for the determination of the conformation of polymer in bulk and experimental details are given about the application of this method to the study of polymeric systems. Measurements have been made for small and intermediate momentum ranges on a series of eight monodisperse deuterated polystyrenes of molecular weight ranging from 21,000 to 1,100,000. The results lead to the concluson that in amorphous state the conformation of the polymer molecule is indistinguishable from that in solvent and that the Debye scattering function which is valid for unperturbed chains applies for q ~1 as low as 10 Á.

Résumé. 2014 Nous examinons les résultats d'expérience de diffusion de neutrons aux petits angles (10-2 q 2 x 10-1 Å-1) par des solutions de sulfonate de polystyrène dans l'eau pour des concentrations supérieures à 0,5 x 10-2 g. cm-3.Avec de l'eau ultra pure, l'absence de diffusion centrale et la présence d'un maximum pour les plus grandes valeurs de q caractérisent la fonction de diffusion S(q). Les deux effets étudiés, variation de la concentration en polyions et addition de sel, conduisent à des résultats différents : la position du maximum varie avec la concentration de polyions alors qu'avec l'addition de sel, on note l'apparition de diffusion centrale et disparition du maximum.Abstract. 2014 Solutions of polyelectrolyte are studied by small angle neutron scattering for c > 0.5 x 10-2 g. cm -3.The function S(q) is characterized by a small value of S'(q ~ 0) and one broad maximum for higher q's

No abstract

Using the neutron scattering technique, we have measured the temperature dependences of the characteristic correlation lengths in semidilute polymer solutions in the vicinity of the theta (Θ) point. From the analysis of the data in the Guinier range, with a sample containing a few labeled chains, we find that the radius of gyration Rg has the dependence Rg∼τ0.125±0.005, where τ is the reduced temperature (T−Θ)/Θ. The scattering experiment from unlabeled samples, in the intermediate range of the momentum transfer, shows a decrease of the screening length ξ, ξ∼τ−0.25±0.01. These two dependences are in agreement with a recent calculation [M. Daoud and G. Jannink, J. Phys. (Paris) (to be published)] based on de Gennes’s theory that the theta temperature is in fact a tricritical point. A scaling law in molecular weight and concentration is tested below Θ. A temperature concentration diagram is drawn with the above mentioned experimental results.

No abstract

No abstract

Neutron scattering experiments on a partially labeled gel and quasi-elastic light scattering measurements are reported. The radius of gyration of the elementary mesh of the labeled network is shown to remain nearly constant when the gel is deswollen by a factor of 4 in volume. This result is in contradiction with the fundamental hypothesis of the classical theories of gel swelling; however, it can be understood by considering a rearrangement of the network at a scale larger than the mesh. The cooperative diffusion constant Dc of the osmotically deswollen gels was measured by using the quasi-elastic light scattering. The apparent scaling law of D0 vs. , the polymer volume fraction of the gel, is shown to differ significantly from that corresponding to a series of gels swollen at equilibrium in a pure solvent. This result is interpreted in the framework of a phenomenological scaling approach, consistent with the neutron scattering results. This approach allows the calculation of the variation with of Kx and G, the osmotic bulk modulus and the shear modulus of the gel, respectively, which appear in the expression for Dc.