ISSN:
1436-2449
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Summary A critical discussion of therigid rod-like andflexible rod-like groups used most frequently in the design of rod-like mesogenic units is presented. Based on the literature data on the potential energy difference and the rotational energy barrier of their extended and kinked configurational isomers and respectively conformers, we suggest a classification inrigid rod-like groups (the rod-like shape of the molecule is rigid although there is free rotation about some of its C-C bonds, like for example oligo-p-phenylenes, diphenyl-acetylenes, etc., and configurational isomers which require a high rotational energy barrier or activation energy like for example, stilbene),semirigid orsemiflexible rod-like groups (conformationally) flexible but of medium rotational energy barrier like for example aromatic esters and amides) andflexible rod-like groups (conformationally flexible groups which require a low rotational energy barrier, i.e., within the same range of values with that of n-butane, like for example: 1,2-diphenylethane and phenyl benzyl ether derivatives). Therefore,rigid, semirigid orsemiflexible, andflexible refer to the ability of the rod-like molecule to change its rod-like shape.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01032667
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