Determination of the structure factor of polymeric systems in solution by small-angle scattering: A SANS-study of a dendrimer of fourth generation

• Published in: Macromolecular chemistry and physics 2002-10, Vol.203 (13), p.1995-2004
• Main Authors: Rosenfeldt, S., Dingenouts, N., Ballauff, M., Lindner, P., Likos, C. N., Werner, N., Vögtle, F.
• Format: Article
• Language: English
• Subjects: Applied sciences; contrast variation; dendrimers; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; SANS; Solution and gel properties; structure factor
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/1521-3935(200209)203:13<1995::AID-MACP1995>3.0.CO;2-6

The analysis of concentrated solutions of a dendrimer G4 of fourth generation by small‐angle neutron scattering (SANS) is presented. The determination of the structure factor S(q) (q = (4π/λ)sin(θ/2); λ: wavelength of radiation; θ: scattering angle) from experimental data is discussed in detail. It is shown that the incoherent contribution Iincoh to the measured scattering intensity may profoundly disturb the determination of S(q), in particular at high concentrations of the solute molecules. Contrast variation is used to determine Iincoh which is subtracted subsequently from the measured intensities. Moreover, a general method for the check of the data of S(q) for internal consistency is presented. It is based on the expansion of S(q) into powers of q2. The structure factor S(q) obtained from the corrected data is shown to be consistent except at the highest concentration of the dendrimer G4 under consideration here. This finding is explained by a change of the form factor of the dendrimers due to overlap of the particles. The method of analysis presented here is general and can be applied to SANS‐data of other structures as well. Chemical structure of dendrimer G4.