Study of the molecular tilt angle

in non-ferroelectric PBnA liquid crystal family


K. El Guermai1,  K. Elboussiri1, 2*

1 Groupe  « Biomatériaux métalliques » Faculté de Médecine Dentaire,

Rue Vésale, 9157 Casablanca, Maroc

2 UFR plasma hautes énergies et atomiques, Faculté des Sciences, route d’El Jadida, Casablanca, Maroc

* Corresponding author. E-mail:

Received: 22 January 2008; revised version accepted: 03 February 2009



     We present a study of molecular inclination with respect to the normal layers in  the existing domain of smectic A and I phases and at the transition between them in PBnA (phenyl-4 benzylidene 4’-alkylaniline) liquid crystals family.

     First, we go over the methods actually used to define this inclination by calculation. Usually, layers thickness, determined by x-rays pattern diffraction of aligned samples by an external magnetic field, are used in order to approach as much as possible the real values of the molecular inclination.

     In this article, we present an original method to determine the tilt angle in a direct way by observation on polarizing microscope.


Keywords: PBnA liquid crystal; Tilt angle; Ferroelectric.

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