Mixtures of tertiary amine-functionalized mesogens with poly(acrylic acid)

Diethylamine-functionalized alkoxy methoxy biphenyl mesogens of variable sp acer lengths (LC-1,nN, n = 5-12) and their equimolar mixtures with poly(acr ylic acid) (PAA) were investigated by infrared spectroscopy, differential s canning calorimetry, polarizing optical microscopy, and X-ray diffraction. The pure LC-1,nN are polymorphic, generally possessing two different crysta lline phases [a (full or partial) bilayer at ambient temperature followed b y an orthogonal monolayer at higher temperatures], whose detailed character istics depend on the spacer length. The mesogen melting point (a lamellar E -like-isotropic transition) is independent of spacer length. The equimolar LC-1,nN/PAA mixtures are biphasic, composed of a mesogen-pure phase and a p hase composed of a polymer-mesogen complex resulting from proton-transfer i nteractions. The former is unperturbed by the presence of the latter. The c omplexes are liquid crystalline, most likely in the form of a partial or in terdigitated smectic A mesophase. The smectic- isotropic transition tempera tures are generally higher than the mesogen melting points and increase str ongly with spacer length.