LCPs can be transformed into liquid crystals with more than one method. However, the distinction is not rigidly defined. Based on the mechanism of aggregation and ordering, LCPs can be roughly divided into two subcategories as shown below. Mesogens in LCPs can self-organize to form liquid crystal regions in different conditions. Mechanism The mechanism for lyotropic systems (L means liquid, LC means liquid crystal, Vp means the volume fraction of the polymer, T means temperature.) Therefore, Latin letters are used to help the classification of LCPs. However, by introducing flexible spacers between the backbones and the mesogens, the ordering of mesogens can be decoupled from the conformation of the backbones.īecause of the researcher's effort, more and more LCPs of different structures are synthesized. If the mesogens are directly linked to the backbones, the coil-like conformation of the backbones will impede the mesogens from forming an orientational structure. The mesogens usually are linked to the backbones through flexible spacers (Although for a few LCPs, the side chains directly link to the backbones). In side-chain LCPs, the mesogens are in the polymer side chains. To make this kind of polymer easy to process, different methods are applied to lower the transition temperature: (1) Introducing flexible sequences (2) Introducing bends or kinks (3) Adding substituent groups to the aromatic mesogens. Main chain LCPs have rigid, rod-like mesogens in the polymer backbones, which indirectly leads to the high melting temperature of this kind of LCPs. The basic structures for these two kinds of LCPs are shown in the figure. To contrast, side chain liquid crystal polymers (SCLCPs) have pendant side chains containing the liquid crystal cores. Main chain liquid crystal polymers (MCLCPs), as the name indicates, have liquid crystal cores in the main chain. LCPs are categorized by the location of liquid crystal cores. More information about the mesophases can be found on liquid crystal page.Ĭlassification Structure of LCPs The mesogen cores of the polymers will aggregate into different mesophases: nematics, cholesterics, smectics and compounds with highly polar end groups. Same as the small molecular liquid crystal, liquid crystal polymers also have different mesophases. The class of polar and bowlic LCPs, with unique properties and important potential applications, remains to be exploited. In fact, the high ease of forming of LCPs is an important competitive advantage against other plastics, as it offsets high raw material cost. Today, LCPs can be melt-processed on conventional equipment at high speeds with excellent replication of mold details. Processing of LCPs from liquid-crystal phases (or mesophases) gives rise to fibers and injected materials having high mechanical properties as a consequence of the self-reinforcing properties derived from the macromolecular orientation in the mesophase. In a similar way, several series of thermotropic LCPs have been commercially produced by several companies (e.g., Vectra / Celanese).Ī high number of LCPs, produced in the 1980s, displayed order in the melt phase analogous to that exhibited by nonpolymeric liquid crystals. Chemical structure of this aramid consists of linearly substituted aromatic rings linked by amide groups. ![]() In solid form the main example of lyotropic LCPs is the commercial aramid known as Kevlar. Liquid-crystal polymers are present in melted/liquid or solid form. Liquid crystallinity in polymers may occur either by dissolving a polymer in a solvent ( lyotropic liquid-crystal polymers) or by heating a polymer above its glass or melting transition point ( thermotropic liquid-crystal polymers). One of the most famous and classical applications for LCPs is Kevlar, a strong but light fiber with wide applications, notably bulletproof vests.īackground Molecular structure of Kevlar Molecular structure of the LCP Vectran ![]() Therefore, they can be good actuators and sensors. In addition, LCPs have unique properties like thermal actuation, anisotropic swelling, and soft elasticity. They are widely used in the digital display market. They are both crosslinked LCPs but have different cross link density. Despite uncrosslinked LCPs, polymeric materials like liquid crystal elastomers (LCEs) and liquid crystal networks (LCNs) can exhibit liquid crystallinity as well. Liquid crystal polymers (LCPs) are polymers with the property of liquid crystal, usually containing aromatic rings as mesogens. WikiProject Chemicals may be able to help recruit an expert. The specific problem is: Needs to be updated with newer research and applications of LCPs. ![]() This article needs attention from an expert in Chemicals.
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