Liquid crystalline polymers containing heterocycloalkane mesogens. 2. Side-chain liquid crystalline polysiloxanes containing 2,5-disubstituted-1,3-dioxane mesogens

Polysiloxanes and copolysiloxanes containing 2-(p-hydroxyphenyl)-5-(p-methoxyphenyl)-1,3-dioxane and 5-(p-methoxyphenyl)-1,3-dioxan-2-yl as mesogenic units and an aliphatic spacer containing 11 and 10 methylene units, respectively, were synthesized. Their phase behavior was studied by differential scanning calorimetry and optical polarization microscopy, and compared with the phase behavior of the polysiloxanes and copolysiloxanes containing 4-methoxy-4′-hydroxybiphenyl and 4-cyano-4′-hydroxybiphenyl mesogens attached to the polymer backbone through an aliphatic spacer containing 11 methylene units. All synthesized polymers present smectic mesomorphism. The polymers containing 4-methoxy-4′-hydroxybiphenyl and 4-cyano-4′-hydroxybiphenyl are also crystalline, while the polymers containing 1,3-dioxane based mesogens do not crystallize.