Mesogenic Schiff's Base Esters with a Methoxyethyl Tail

Abstract

Two new mesogenic homologous series, each consisting of a methoxyethyl tail and a Schiff 's base central linkage, have been synthesized by condensing 2-methoxyethyl 4-aminobenzoate with different 4-n-alkoxybenzaldehydes or 4-n-alkoxybenzoyloxybenzaldehydes to give series I and series II, respectively, and their mesomorphic behavior was studied. In series I, 2-methoxy ethyl 4-(4 0 -n-alkoxybenzylidine)aminobenzoates, the n-butoxy derivative is nonmesogenic whereas higher homologues exhibit the SmA mesophase. In series II, 2-methoxyethyl 4 00 -[4-(4 0 -n-alkoxybenzoyloxy)benzylidene]aminobenzoates, all the twelve compounds synthesized exhibit mesomorphism. Methoxy to n-octyloxy derivatives exhibit an enantiotropic nematic mesophase. The smectic A mesophase commences from n-propoxy derivative and persists up to the last homologue synthesized. The mesomorphic properties of both series are compared with each other and also with the properties of other structurally related series to evaluate the effects of the ethoxyethyl chain on mesomorphism.

Mesogenic cinnamates with a substituted ethyl terminal chain

“…The tendency of rising transition curve has been considered to be a characteristic of low-melting mesogenic homologous series. Table 3 provides a comparison of smectic mesophase range, transition temperatures and molecular structure of representative compounds 10 and 22 (n512) of the present series I and II, respectively, as well as structurally related compounds A [32], B [23], C [27], D [33], E [25], F [28] and G [34]. The smectic range of compound 10 is about 39uC, whereas that of compound 22 is 47uC.…”