Textural changes, melting temperatures

Characterization of the optical textures of LCPs is key in the identification of the specific phases present and in understanding the structure and its relation to the solid state properties. Dynamic hot stage microscopy experiments, with video tape recording attachments, provide images of the texture changes associated with phase changes, as a function of temperature and time. The majority of the optical textures reported in the literature are of either melt or melt-quenched structures, although recently the optical textures... 

Metamorphic rocks are those that have been altered in the solid state by temperature and pressure. The texture and/or composition of the original rock changes over time, but the rock never melts (otherwise it would be igneous). There are two basic types of metamorphic rocks contact and regional. 

In our real-time studies, the 12.6 A peak was monitored as a function of temperature for samples of BP6L fibers which showed two sets of perpendicular arcs. Fig. 3 shows a plot of intensity versus 26 for the meridional arc as a function of temperature. As temperature was increased, the intensity of the 12.6 A peak can be seen to decrease. This decrease, which occurred at 120°C for the meridional arc, was observed to take place at 160°C for the equatorial arc. Both transitions took place at temperatures where the sample clearly showed liquid crystallinity by optical microscopy, but no change in texture. Such observations suggested that different species were responsible for the two different transition temperatures however, these transitions were not readily identified with any visually observed melting or clearing transition. 

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