mesogen?

Aquest terme està format per meso– (‘intermedi’) + –gen (‘que produeix’). Atès que el formant -gen és àton, la síl·laba tònica es desplaça al formant del davant. Per tant, cal escriure mesogen (sing.), mesògens (pl.).

El concepte de mesogen està estretament relacionat amb el de cristall líquid, però el mesogen és el compost que pot originar, sota determinades condicions, una mesofase, és a dir, un cristall líquid. En aquest fragment del document RIPDRI, Is. 12 PRSOAL ATHO (S) V. Percec, H. Jonsson and D. Tomazos. Contract, 1828, 14.90-J, es pot veure clarament la relació entre els dos termes:

A liquid crystalline or mesomorphic phase or mesophase refers to a state of matter in which the degree of order is between the almost perfect long-range positional and orientational order present in solid crystals and the statistical long-range disorder characteristic of isotropic or amorphous liquids and gases. Mesogens or mesogenic groups are compounds which under suitable conditions give rise to mesophases. They can be classified in non-amphiphilic (i.e. most frequently compounds exhibiting a rod-like or disc-like shape) and amphiphilic (i.e. compounds that contain within the same molecule lipophilic and hydrophilic groups which have the ability to dissolve in organic solvents and water respectively). Thermotropic mesophases are induced by a change in temperature, while lyotropic mesophases are induced by a solvent. Some mesogens can generate amphotropic mesophases, i.e. the liquid crystalline phase can be induced either by a change in temperature, by a solvent, or by both.