Scattering from self-assembled systems

The characterization of the structure of polymer nanocomposites by the techniques of small-angle scattering of neutrons and X-rays is reviewed. Within a concise introduction to elastic small-angle scattering, the basics of shape, structure, and interactions of particles are presented, as well as the scattering from polymer chains. The scattering properties of polymer chains can be described within models that can also account for stress-strain properties. In neutron scattering, stretched polymer chains and their fluctuation width can be directly accessed by taking advantage of the difference in the scattering length between H and D atoms. Further, SANS can equally cope with the mounting interest in the characterization of polymers in nowadays popular multiphase materials. Using contrast matching or a combination of two probes, i.e. neutrons and x-rays, the solid phase can be made invisible or visible. This allows to extract new structural information about the rubbery matrix that could not be obtained separately by other methods. Current literature on filler scattering in polymer nanocomposites will be reviewed. The most common fillers where scattering has been shown to be decisive are carbon black, silica, polymeric fillers, and, to a lesser extent, clay. Scattering is a powerful tool to analyse the filler structure in a non destructive way, in the dry (pure filler) state, in solution, or inside macroscopically thick nanocomposite samples. The scattered intensity is obtained as an average over the complete sample, thereby decreasing the impact of possible artefacts as it might be the case in direct-space imaging. In this review part, it is attempted to give an overview of the morphology of the hard component typically encountered in filled polymer systems, its modes of deformation as the sample is deformed, as well as a summary of possible routes of data interpretation and modelling.

Structural and Mechanical Properties of Different Nanocomposites: Silica-Latex, Ferro-Latex, and Silica-Microemulsions

A static light scattering (SLS) study of bovine serum albumin (BSA) mixtures with two anionic graft copolymers of poly (sodium acrylate-co-sodium 2-acrylamido-2-methyl-1-propanesulphonate)-graft-poly (N, N-dimethylacrylamide), with a high composition in poly (N, N-dimethylacrylamide) (PDMAM) side chains, revealed the formation of oppositely charged complexes, at pH lower than 4.9, the isoelectric point of BSA. The core-corona nanoparticles formed at pH = 3.00, were characterized. Their molecular weight and radius of gyration were determined by SLS, while their hydrodynamic radius was determined by dynamic light scattering. Small angle neutron scattering measurements were used to determine the radius of the insoluble complexes, comprising the core of the particles. The values obtained indicated that their size and aggregation number of the nanoparticles, were smaller when the content of the graft copolymers in neutral PDMAM side chains was higher. Such particles should be interesting drug delivery candidates, if the gastrointestinal tract was to be used.

The synthesis, characterization and liposome insertion of a novel magnesium(II) carboranyl-porphyrazine, i.e. [2,3,7,8,12,13,17,18-octakis(1,2-dicarba-closo-dodecaboranyl)-hexylthio- 5,10,15,20-porphyrazine]magnesium(II) complex, MgHECSPz, are described. MgHECSPz was designed to improve the potentiality in multiple approach anticancer therapy. Liposomal formulations with different surface charge were prepared as delivering agents. The obtained loaded vectors were characterized by DLS, SAXS, SANS and zeta potential measurements in order to define the overall properties and structural details of loaded liposomes. (c) 2007 Elsevier B.V All rights reserved.