Dielectric and IR spectroscopy of the macromolecular reaction of anhydridization in a functionalized side-chain liquid crystalline copolymer containing acrylic acid groups
S. Zhukov et al., Dielectric and IR spectroscopy of the macromolecular reaction of anhydridization in a functionalized side-chain liquid crystalline copolymer containing acrylic acid groups, MACROMOLEC, 34(11), 2001, pp. 3615-3625
The anhydrization reaction has been investigated in functionalized side-cha
in random liquid crystalline (LC) copolymers containing cyanobiphenyl mesog
enic and acrylic acid (38 mol %) groups. Heat treatment of the LC copolymer
at 130 degreesC for 5-200 h is accompanied by formation of intra- and inte
rmolecular anhydrides and network structures causing an increase of the gla
ss transition and clearing temperatures. The influence of annealing on the
reorientational dynamics of the copolymers was investigated by broad-band d
ielectric relaxation spectroscopy. The local dynamics of the side group inv
olving spacer motion (gamma relaxation) and mesogen rotation about the long
axis (beta relaxation) do not depend on the annealing time. At the same ti
me a considerable (more than 2 orders of magnitude) decrease in the relaxat
ion rates of the cooperative delta and alpha processes was observed due to
a gradual increase in the main-chain rigidity during the annealing. The mol
ecular mechanism of all relaxation processes detected is discussed.