Low molecular weight liquid crystals LMWLC

SINCE the discovery of liquid crystalline phenomenon for low molecular weight liquid crystals (LMWLCs) more than 100 years ago, anisotropic ordering behaviors of liquid crystals (LCs) have been of considerable interest to academe [1-8], In the 1950s, Hory postulated the lattice model for various problems in LC systems and theoretically predicted the liquid crystallinity for certain polymers [1-3], As predicted by the Hory theory, DuPont scientists synthesized lyotropic LCPs made of rigid wholly aromatic polyamide. Later, Amoco, Eastman-Kodak, and Celanese commercialized a series of thermotropic main-chain LCPs [2]. Thermotropic LCPs have a unique combination of properties from both liquid crystalline and conventional thermoplastic states, such as melt processibility, high mechanical properties, low moisture take-up, and excellent thermal and chemical resistance. Aromatic main-chain LCPs are the most important class of thermotropic LCPs developed for structural applications [2,4-7]. Because they have wide applications in high value-added electronics and composites, both academia and industry have carried out comprehensive research and development. 

Before leaving the topic of LCP/LCP blends, one additional point needs to be stressed. Low molecular weight liquid crystals (LMWLC s) of the same mesophasic class often show miscibility (Gray and Windsor 1974). On the other hand, TLCP s that form the same mesophase, usually nematic, do not necessarily exhibit complete miscibility. Thus, in order to be able to implement the ideas of the last several paragraphs, caution must be exercised in choosing the two LCP s to form the miscible blend. 

The liquid crystallinity of low molecular weight liquid crystals (LMWLCs) was found more than 100 years ago, when Reinitzer synthesized several esters of cholesterol. In the liquid crystalline (LC) state, the substance shows characteristics of a liquid in terms of its mobility, while it exhibits characteristics of a crystalline material in terms of its optical properties because of the anisotropy in the structure (1,2). 

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