G. Galli et al., SYNTHESIS AND THERMOTROPIC PROPERTIES OF NEW POLYACRYLATES CONTAININGALKANOYL-SUBSTITUTED AZOBENZENE MESOGENS, Liquid crystals, 16(1), 1994, pp. 115-125
The synthesis and characterization of a series of new polyacrylates 1,
containing the azobenzene mesogen spaced from the backbone by a hexam
ethylene segment and substituted in the 4-position by an alkanoyl chai
n of variable length, together with those of the relevant precursors a
re reported. Optical and X-ray analyses provided evidence for the pres
ence of a smectic A mesophase in a fairly broad range of temperature i
n both polymers and low molar mass compounds. In polyacrylates 1, the
side-chain substituents were fully interdigitated in a smectic A, stru
cture. The comparison of the transition parameters of polymers 1 with
those of another series of polyacrylates 7 containing the azobenzene u
nit substituted in the 4-position by an alkyloxy chain of variable len
gth revealed that the replacement of an oxygen atom by a carbonyl grou
p strongly enhanced the smectogenic character of the azobenzene group.