HIGH-PRESSURE FIBER OPTIC LIGHT-SCATTERING SPECTROMETER

A high-pressure fiber-optic light-scattering spectrometer has been con structed for in situ observation of molecular dissolution/association as well as the polymerization process in supercritical fluids. Single (or multiple) fiber-optic probes, each comprised of a single optical f iber (or multiple optical fibers) and a graded index microlens, are us ed to transmit the incident laser beam and to receive the scattered li ght as well as the transmitted light from the high pressure cell. The direct immersion in the scattering medium of the fiber-optic probes ma kes the spectrometer more compact and more flexible with an easier ali gnment process. With the miniaturization and flexibility, our high-pre ssure light-scattering cell can be transported and adapted in combinat ion with other physical techniques, such as synchrotron small angle x- ray scattering which requires a different set of windows (e.g., made o f diamond) suitable for x-ray transmissions. This spectrometer has bee n successfully used for the in situ study of the molecular association behavior of a diblock copolymer of 1,1-dihydroperfluorooctylacrylate and vinyl acetate in supercritical carbon dioxide under pressures up t o 552 bar. (C) 1998 American Institute of Physics.