Organic Mesophases

One of the most interesting features of SCLCPs is related to the fact that a liquid crystalline phase can be orientated and frozen by cooling it to below the glass transition temperature. It is therefore necessary to drive SCLCP systems from microscopic self-organized mesophases to macroscopic order. 

Liquid crystals (LCs) are molecules that have the ability to self-assemble into organized mesophases with properties intermediate between those of crystalline solids and isotropic liquids [1,2]. In LC phases, the molecules are dynamic and collectively behave as a viscous liquid but retain on average a degree of organization reminiscent of an ordered, crystalline solid. Consequently, they can be considered ordered fluids, as a more accurate definition. LCs can be subdivided into two general classes—thermotropic LCs and lyotropic LCs—depending on the environmental and molecular factors that govern how they form ordered fluid phases. 

Perfluoroalkyl segments, -(CF2)nF, are intrinsically liquid-crystalline and can be used as building blocks in self-assembling materials. In combination with other units, such as short alkyl segments, they generate highly organized mesophases [97], Another important property of the semi-fluorinated moieties is that they can... 

The complexation of amphiphilic molecules with functionalized polymers forms layered smectic structures [94-97]. Polymeric complexes 41 consisting of poly(vinylpyridine) and an alkylphenol also form layered organized mesophases [94]. The incorporation of this structure into block copolymers with polystyrene results in the self-organization in two length scales, that is, block copolymer length and nanoscale length [95, 96]. 

The different types of molecular organization (mesophases) that can be found are shown in Figure 1.30 namely smectic and nematic (also cholesteric for polymers with a chiral centre). Nematic structure is seen in polymers with stiff main chains, and such polymers are readily processed and have excellent... 

Figure 1.30 Different types of molecular organization (mesophases) which are cor observed (a) smectic, (b) nematic.

The structure of PMCS-6 mesophase cannot be described in terms of the conventional classification used for organic mesophase polymers. From our viewpoint, PMCS-6 are the novel class of mesomorphic systems. 

Highly organized mesophase/ smectic-A (C), or highly organized mesophase/nematic 40... 

Highly organized mesophase/ highly organized mesophase 150... 

The final section deals with the problem of intermolecular organization in block copolymer solutions. For dilute solutions in a selective solvent, we discuss micelle formation. For nonselective solvents, we analyze the formation of various organized mesophases. Also in these systems excluded volume interactions lead to nontrivial subtle effects. ... 

The phenomenon of thermotropic liquid crystallinity has been known at least since 1888. Since the early observations by Reinitzer and Lehmann of unusual melting behavior in certain organic compounds, mesogenic compounds have been both actively sought and incidentally discovered. Several relatively recent discoveries have shown the technological utility of organic mesophases. Substantial impetus has thus been provided for the systematic investigation of the relationships between molecular structure and liquid crystallinity. 

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