Igor Dolbnya

Recent experiments on a small‐angle/wide‐angle X‐ray scattering beam line at the ESRF

Recent results using a new combined small-angle/wide-angle X-ray scattering (SAXS/WAXS) beam line at the European Synchrotron Radiation Source (ESRF) will be presented. This beam line is specifically designed to be able to handle complicated sample environments required to perform time-resolved experiments mimicking processing conditions used in material science. Besides the attention that has been given to the interfacing of these sample environments to the beam line data acquisition system also the developments in detector technology will be discussed. The influence that a high count rate and low noise WAXS detector can have on the accuracy of experimental results in polymer crystallisation will be shown. It is shown that it is feasible to detect crystalline volume fractions as low as 10 -3 -10 -4 in polymeric systems.

Polarized luminescence from self-assembled, aligned, and cleaved supramolecules of highly ordered rodlike polymers

A hierarchical self-assembly in comb-shaped supramolecules of conjugated rodlike polymers is reported. The supramolecules consist of poly(2,5-pyridinediyl), acid dopants, and hydrogen bonded alkyl side chains. A thermotropic smectic state with an exceptionally large coherence length is formed without additional solvent. This allows facile overall alignment resulting in high dichroism and polarized photoluminescence. Solid films are formed by cleaving side groups from the supramolecules which retain the optical anisotropy together with the high photoluminescence quantum yield of pristine polymer.

In situ study of the formation of CdS nanoparticles by small-angle X-ray scattering

Time-resolved in situ small angle X-ray scattering measurements were carried out to monitor the formation of nanoparticles of cadmium sulfide, from a solution containing the corresponding acetate and thioacetamide under solvothermal conditions. Analysis of the SAXS data shows that spherical cadmium sulfide particles of ca 105 A in radius form within the first minutes of the reaction and then grow uniformly to form cylindrical nanoclusters over a period of a few hours, resulting in a highly monodispersed particles distribution.

Diffraction analysis of highly ordered smectic supramolecules of conjugated rodlike polymers

A small/wide-angle X-ray scattering and grazing incidence diffraction study of comb-shaped supramolecules of conjugated poly(2,5-pyridinediyl), acid dopant and hydrogen bonded amphiphilic side chains is reported. In solution, polymers are dissolved rodlike particles. When the side-chains are introduced, polymers self-assemble in hierarchic liquid crystals (LC). Diffraction patterns of aligned LC show h00, 020, and 004 reflections, and additional small-angle reflections along the polymer axis. A triangular correlation function indicating a very large correlation length is seen along the smectic axis. An aligned solid structure can be formed by cleaving side chains from the aligned LC.

Shear-induced crystallization of polyethylene studied by small- and wide-angle X-ray scattering (SAXS/WAXS) techniques

Shear induced crystallization of commercial grade polyethylenes (PE) have been investigated using simultaneous SAXS and WAXS, enabling real time studies of the kinetics and structure development to be performed.

Self-Assembled, Aligned, and Cleaved Supramolecules of Poly(2,5-pyridinediyl)

We report on directed self-assembly in supramolecules containing rod-like polymers. The comb-shaped supramolecules consist of poly(2,5-pyridinediyl), camphorsulfonic acid, and hydrogen bonded amphiphilic side chains. Locally they form highly ordered lamellar structures in which the polymers are stacked. The liquid crystalline state allows facile overall alignment yielding absorption dichroism and polarized photoluminescence. After alignment, cleavage of the amphiphiles results in solid films which retain this optical anisotropy with the high photoluminescence quantum yield.