Short-Pulse X-Ray Optics: Effects and Considerations
Newer synchrotron radiation sources should provide sub-picosecond x-ray pulse durations. Various optics considerations for such short pulses will be addressed, including temporal broadening effects, pulse length preservation, and possibilities of further compression.
we report a low frequency mechanical relaxation study of molecular motions near and below glass transition in side chain liquid crystal polymers (SCLCP) in the cholesteric state. The SCLCP was a blend of crosslinked and uncrosslinked materials. Different compositions were studied. These materials exhibit low temperature relaxation processes and a main relaxation connected to the glass transition. Localiscd motions arc responsible for the low temperature processes while the main relaxation exhibits cooperative features and is sensitive to the amount of crosslinked fraction. The relaxation blue in the glass transition range when plotted against normalised reciprocal temperature shows that the molecular motions display a fragile character in agreement with the highly cooperative feature and strong physical aging effects. These observations are discussed in the frame of correlated motions involved in the liquid glass transition.