X-ray photon correlation spectroscopy studies of the dynamics of self-assembling block copolymer structures

Abstract

Several improvements presented to the emerging technique of X-ray Photon Correlation Spectroscopy. These improvements enabled the study of polymer structures, in particular isotropic sponge phases of homo-polymer block copolymer mixtures. An analysis is presented on how to optimize the experimental beamline configuration for achieving the best possible signal-to-noise ratio (SNR) in x-ray photon correlation spectroscopy (XPCS) experiments. A new, fast x-ray detector system is developed for high-throughput, high-sensitivity, time-resolved, x-ray scattering and imaging experiments, most especially x-ray photon correlation spectroscopy (XPCS). The new detector is characterized in detail, and its performance is evaluated in terms of its signal to noise ratio. Data analysis and photon discrimination techniques are discussed in conjunction with the high data rates this detector produces. The improved detector is capable of collecting the same quality XPCS data in fifty times shorter time than previously available detectors. Detailed characterization of polystyrene ethylenebuthylene styrene sponge phase block copolymer samples is presented. Static X-ray scattering is employed to explore the structure of block copolymer sponge phase samples. The dynamics of the polymer samples is probed by X-ray Photon Correlation Spectroscopy, providing the first measurements on the dynamics of a block-copolymer sponge phase. The structural movements are studied at length scales both longer and shorter than the characteristic length scale of the sponge structure.

(cont.) The intermediate scattering function (ISF) is measured in the 2 ms-200 s range of delay times and 0.01-0.2 nm⁻¹ range of wavenumbers. Both the shape and characteristic delay time of the of the ISF is studied versus temperature and concentration of samples. The results are compared with relevant theories.