Copolyethers, liquid crystalline

Optical texture observations and X-ray investigations showed that the polyacrylate 41 PA 3 and the copolymer 45 (x=0.8) form nematic phases. The polymethacrylate 41 PMA 3 and the copoly ether 45 (x=0.55) display no liquid crystallinity at rest, but exhibit a virtual isotropic liquid-nematic transition a few degrees below Tg, as evidenced by miscibility studies. Copolyether 46 does not show any threaded or schlieren texture, which would be characteristic of a nematic. 

The values of and r=d2 ld2i predicted by the different theoretical models and the resulting evaluation of SHG enhancement with liquid crystalline axial order are given in Table 24 for polyacrylate 41 PA 3 and copolyether 45 (x=0.8). The data in Table 24 confirm that it is possible to gain in net polar ordering by starting from a liquid-crystalline system. The enhancement of the NLO performance with liquid-crystalline order is by a factor of 2.3-3.3 in qualitative agreement with the SKS [156] and MS VP [157-159] model results. It should be noted, however, that the measured order parameters (P2) are lower than the calculated... 

Thisayukta J, Nakayama Y, Kawauchi S, Takezoe H, Watanabe J (2000) Distinct formation of a chiral smectic phase in achiral banana-shaped molecules with a central core based on a 2,7-dihydroxynaphthalene unit. J Am Chem Soc 122 7441-7448 Tschierske C, Dantlgraber G (2003) From antiferroelectricity to ferroelectricity in smectic mesophases formed by bent-core molecules. Pramana J Phys 61 455-481 Ungar G, Percec V, Zuber M (1992) Liquid crystalline polyethers based on conformational isomerism. 20. Nematic-nematic transition in polyethers and copolyethers based on l-(4-hydroxyphenyl)2-(2-R-4-hydroxyphenyl)ethane with R=lluoro, chloro and methyl and flexible spacers containing an odd number of methylene units. Macromolecules 25 75-80 Urayama K (2007) Issues in liquid crystal elastomers and gels. Macromolecules 40 2277-2288 Vorlander D (1908) About transparently clear, crystalline liquids. Rep Ger Chem Soc 41 2033-2052... 

By using a homogeneous mixture of PO-EO, containing 20-25% PO, the resulting PO-EO copolyether is liquid because the PO units perturb the regularity of the long poly[EO] chains which also disturbs their tendency to organise themselves into crystalline structures. 

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