Millisecond time-resolved x-ray diffraction on liquid-crystalline phase transitions using infrared laser T-jump technique and synchrotron radiation

Abstract

An erbium laser (λ=1.5 μm) with a pulse energy of 2 J delivered in 2 ms was used for rapid heating to investigate the kinetics and structural mechanism of the thermotropic phase transitions of a phospholipid/water system by fast x-ray small-angle powder diffraction. The phase transitions were induced by a single laser pulse, leading to a T jump of about 10 °C and the structural relaxations following the T jump were detected in 1-ms resolution. The results show that the transition at 29 °C (Lβ-Lα) is at least as fast as the heating time (2 ms) and that the lamellar/hexagonal transition around 57 °C (Lα-HII) is considerably slower with a half-time of the order of 100 ms.