Рубрики:
CONJUGATED POLY(AZOMETHINE)S
TERMINAL SUBSTITUENTS
ELECTRONIC-STRUCTURES
FLUORINATED ANALOGS
INTERNAL-ROTATION
MOLECULES
COMPOUND
ANGLES
STATE
NMR
Кл.слова (ненормированные):
azomethines -- benzylideneaniline -- conformation -- steric effects of substituents -- nematic-isotropic liquid transition -- conformational polymorphism
CONJUGATED POLY(AZOMETHINE)S
TERMINAL SUBSTITUENTS
ELECTRONIC-STRUCTURES
FLUORINATED ANALOGS
INTERNAL-ROTATION
MOLECULES
COMPOUND
ANGLES
STATE
NMR
Кл.слова (ненормированные):
azomethines -- benzylideneaniline -- conformation -- steric effects of substituents -- nematic-isotropic liquid transition -- conformational polymorphism
Аннотация: The interaction of the conformational degrees of freedom of azomethines in the nematic phase, which is induced by electronic donor-acceptor properties of the terminal substituents of the benzylideneaniline core is studied. These degrees of freedom related to the rotation angles phi (k) around the bonds between the substituent and the aniline ring (phi(1)) and also between the CH=N bridge and the aniline ring (omega(2)) are characterized by the parameters Q (k) = aOE (c) cos(2)phi (k) >. It is found that the interaction of these degrees of freedom is manifested in the linear dependence Q (2)(Q (1)). Within the phenomenological theory the effect of this interaction on changes delta (k) in the Q (k) values during the nematic liquid crystal-isotropic liquid phase transition is revealed along with the temperature T (NI) and character of this transition. The derivation of previously established empirical dependences T (NI)(Q (k) ) is presented in the presence of direct and indirect steric effects of side substituents affecting the Q (k) values. A diverse combination of delta (k) signs in the nematic phase, which is a prerequisite for the conformational polymorphism of the nematic phases of azomethines, is shown.
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Доп.точки доступа:
Аверьянов, Евгений Михайлович