Michele Floriano

Small angle scattering study of the structure of isotactic polypropylene-hydrogenated oligo(cyclopentadiene) blends☆

Abstract Blends of isotactic polypropylene ( i PP) and hydrogenated oligo cyclopentadiene (HOCP) have been studied by means of small angle X-ray scattering in the temperature range 70–160°C. The structure of blends containing less than 25% HOCP is very similar to the one of plain i PP, i.e. lamellae whose thickness increases by increasing the temperature. Blends containing more than 25% HOCP are characterized by two kinds of lamellae formed by layers of i PP and amorphous material rich in i PP and in HOCP, respectively. The crystallizable i PP present in both phases crystallizes from the melt, in analogy to what happens in HDPE/HOCP blends and in agreement with the values of the crystallinity referred to the crystallizable polymer, that is almost constant with composition for both blends.

Application of the small-angle neutron scattering technique to the study of solubilization mechanisms of organic molecules by micellar systems

Abstract We present the possible contribution of the small-angle neutron scattering (SANS) technique to the molecular interpretation of the solubilization phenomena in simple micellar systems. We show for a few ternary micellar systems, that an appropriate analysis of SANS experimental data can provide information on modifications induced on micellar dimension, shape, number of monomer, and charge and on the partition coefficient of the additive and its localization inside the micellar aggregate. The influence of n -alcohols on the thermodynamics and on the structure of sodium dodecyl sulphate (SDS) aqueous solution has been extensively investigated, so the agreement between the results obtained in previous work and those obtained in this study allows the validity of data analysis procedure to be verified. The study of SDS and dodecyltrimethylammonium bromide (DTAB) solutions, containing alternatively five different macrocycles showed that: in the case of SDS solution different, but in all cases appreciable, amounts of solute were found to be localized in the micellar phase, while for most DTAB solutions there was evidence for their localization in the aqueous phase. By analysing the single system, it was not possible to establish whether the solute was in the “core” or in the “shell” of the aggregate, but from a comparison between the results related to the two surfactant systems and from the different molecular properties of the macrocycles it was possible to localize each of them inside the aggregate and to explain the different amounts found.

Identification Techniques II

An overview of applications of Small Angle X-ray Scattering (SAXS) techniques to topics of interest in the field of Cultural Heritage is presented. The basic concepts of the technique, a description of sources and laboratory instrumentation and some models and methods for data analysis are discussed. Applications of SAXS to various kinds of materials are reported to obtain information on the structure useful to shed light in some subjects such as preparation, physical treatment, traceability and degradation of materials.

Small-Angle Scattering from Phase-Separated Metallic Alloys: From Experiment to Phase Diagrams

In this paper, phase-separated metallic alloys are described in terms of concentration fluctuations. As a consequence, Small Angle Scattering equations which allow to calculate the entire scattering curve by incorporating particle-particle interference effects on the basis of the Percus-Yevick formalism, are obtained. It is shown that, for Aluminium-Lithium alloys, satisfactory fits of the experimental data can be obtained if it is assumed that Li rich elliptical monodisperse precipitate particles approach each other at average distances which are larger than the sum of the hard-sphere particle radii. It is also shown that a possible ambiguity of this model, within the Percus-Yevick formalism, can be avoided if the particle-particle interaction potential is assumed to be the sum of a hardsphere part plus a finite repulsive step. Small Angle Scattering techniques are important when structural information is needed in the early stages of the phase decomposition, and is complementary to the more widely used Transmission Electron Microscopy, the ideal technique when the size of the fluctuation regions is of the order of 100 nm or larger.

Small Angle Neutron Scattering from Systems of Interacting Particles. Modelling High Density Micellar Fluids

The need for analytical solutions of the scattering equation for complex situations (polydisperse samples, scattering from non centrosymmetrical particles, etc.) has somehow escaped the attention of the workers in the Small Angle Scattering field, although it is clear that, at the level of sophistication today available for the experiments, a more rigorous approach is necessary. For quite a few years our group has been actively engaged in SANS research and has occasionally devoted its attention to develop alternative ways of data analysis based on more rigorous solutions of the scattering equation.