P-Methacrylylhydroxybenzoic acid

The fact that the structure of a solid monomer influences its polymerization substantially now seems obvious. It is not as clear whether structural phenomena can effect polymerization if the monomer is a liquid. It has long been known that ordered regions or clusters exist in liquids, and several years ago it was assumed that in some cases these regions in liquid monomers can influence the polymerization. One of the most vivid examples—namely, polymerization in the liquid-crystalline state—was accomplished by Krentzel and co-workers (I, 2, 3). The object of their study was p-methacrylylhydroxybenzoic acid, which forms conventional crystals in the pure state and does not polymerize in the solid state. However, when mixed with alkoxybenzoic acid, it forms liquid crystals of both smectic and nematic forms. Polymerization of p-meth-acryllylhydroxybenzoic acid in various forms of liquid crystals was compared with polymerization of the same substance dissolved in dioxane and dimethylformamide (DMF). 

If p-methacrylylhydroxybenzoic acid is mixed with p-cetylhydroxy-benzoic acid, a smectic form of liquid crystals results, but if it is mixed with p-nonylhydroxybenzoic acid, the resulting form is nematic above 104°C. and is smectic below this. This makes it possible to compare the polymerization behavior of the same monomer in solution, where the mutual ordering of its molecules is minimal, in a liquid crystal state with only orientation order (nematic form), and in the liquid-crystal state involving both orientation and coordination order (smectic form). 

The optical anisotropy of the segment of polymer 6 in Table 3.5 (polymers of p-methacrylylhydroxybenzoic acid cetyl ester, PCEM [55]) is ttj - 0x2 = -445 40 cm and the optical anisotropy of the monomeric unit is Aa = -18 10 cm. This value of Aa of PCEM is significantly higher than the optical anisotropy of molecules of polycetyl methacrylate (polymer 5 in Table... 

---

See also in sourсe #XX -- [ ]

---