Synthesis and properties of new side-chain homo- and copolymethacrylates having a cyanobiphenyl unit, aliphatic chains and an interconnecting carbonate linkage

New side-chain homo- and copolymethacrylates containing a 4-cyanobiphenyl unit spaced from the backbone by ethylene and undecane segments, and an interconnecting carbonate linkage were synthesized and characterized by FTIR and H-1 NMR spectra, and elemental analyses. The thermal and mesogenic behaviors were evaluated by differential scanning calorimetry (DSC), polarizing microscope and temperature-dependent X-ray diffraction techniques. The data described that the homopolymer 5f (smectic A) having the undecane segment and the carbonate linkage together with the 4-cyanobiphenyl mesogen in the side chain and only the Sf-rich copolymers (nematic) have thermotropic liquid crystalline (LC) phases. The incorporation of the undecane segment between the carbonate linkage and the 4-cyanobiphenyl unit stabilized the LC phase of the homopolymer 5f. The interconnecting carbonate linkage is unfavorable for LC formation in these types of copolymers. (C) 1997 Elsevier Science Ltd.