Reentrant Nematic phases in Binary Systems of Terminal-Nonpolar Compounds

Frustrated Behavior of a Side-Chain Liquid Crystalline Polyacrylate

“…The re-entrant phenomenon, i. e. the "reentrance" of the less ordered phase at temperatures below those of a more ordered phase, is well known for terminally polar [1] or sterically asymmetric [2,3] liquid crystals. Such behavior, as well as the presence of particular smectic phases in phase diagrams of liquid crystals (LC), is usually described in terms of frustration [4,5] This concept assumes the existence in the system of two or more competing interactions of nearly equal strength which favor different periodicity.…”

Induced Smectic and Nematic Phases and Re-entrant Phenomena

“…The compounds with flexible spacer group: -CH(CH 3 )-CH 2 -COO-and -0-(CH 2 ) 3 -COO-were lately described [123,124]. The evidence was obtained that the reentrancy is not only possible in strong polar systems but also in low polar systems containing calamitic [125] or discotic molecules [126,127] and in mixed systems containing compounds of high and low polarity [46,62,128,129]. The systems including chiral compounds [130,131] and low and high molecular weight [132] compounds are also described.…”

Structure and Dynamics of Reentrant Nematics: Any Open Questions after Almost 40 Years?

“…Until 1983 it was believed that only molecules with a strong polar group showed a reentrant behavior. However, Diele et al showed the existence of RN phases in terminal-nonpolar substances [ 29 , 30 ]. Importantly, their X-ray measurements showed that the thickness of the S layers is equal to the average molecular length.…”

“…Importantly, their X-ray measurements showed that the thickness of the S layers is equal to the average molecular length. Hence, dimerization cannot take place in these nonpolar compounds and the occurrence of a RN phase must have a different physical origin [ 29 , 30 ] (see Section 4 for the theories applicable to nonpolar systems).…”