ISSN:
0887-6266
Keywords:
liquid crystals
;
crystallization metastable phases
;
rates of phase transformation
;
morphology
;
competition between phases
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The crystallization of the monotropic liquid crystal forming polyether, poly-n-nonyl-4 4′-biphenyl-2-chloroethane, was investigated using DSC calorimetry and polarizing optical microscopy. The principal theme was the nature of crystallization from the nematic liquid crystalline state, which in the monotropic system could be directly compared with the more familiar crystallization from the isotropic melt using one and the same compound. Novel, polarizing optical structures were observed that combine features of both the usual LCPs (fine “grains”) and those of the conventional crystallizeable polymers (spherulites) with differing degrees of prominence of each according to crystallization conditions. The considerations of such structural observations, combined with the calorimetric results and the newly gained information on the kinetics of the crystallization process, reveal an acceleration of the overall crystallization rate at the stage where liquid crystal formation sets in as assessed by calorimetry but not as registered with the polarizing microscope, leading to wider issues regarding the conception of “amorphous crystalline ratio” and its extension to the liquid crystal state. Beyond polymers, the new findings lead to the more general considerations on metastable phases, specifically to their emergence and competition with the phases of ultimate stability. In this respect the present study on a monotropic LCP provides an illustrative example of a more general treatment presented previously. © 1995 John Wiley & Sons, Inc.
Additional Material:
17 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1995.090331304
Permalink
