Polymer Dispersed Liquid Crystals with Nanosized Droplets: SEM, FTIR and UV Spectroscopy Studies

 

Réda Benmouna1*, Vincent Rachet2, Pierre Le Barny2, Patrick Feneyrou2, Ulrich  Maschke3, Xavier Coqueret3.

 

1. University Aboubakr Belkaid, Faculty of Sciences, Department of Physics, Tlemcen BP119, Algeria.

2. Thales Research & Technology, Domaine de Corbeville, F-91404 Orsay Cedex, France

3. Laboratoire de Chimie Macromoléculaire (UMR CNRS 8009), Bâtiment C6, Université des Sciences et Technologies de Lille, F-59655 Villeneuve d’Ascq Cedex, France

 

 

Graphical Abstract

 

 

      Polymer Dispersed Liquid Crystals with nanosized droplets were investigated by SEM, FTIR and UV techniques. The photopolymerization process under radiation curing was monitored by FTIR spectroscopy and the size distribution of droplets was correlated to the conditions of film preparation. Hysteresis and memory effects were evidenced in the electro-optic responses.

 

 

ABSTRACT

 

      Polymer Dispersed Liquid Crystals with nanosized droplets were studied using a chemical formulation consisting of thiol-ene monomers and low molecular weight liquid crystals. The morphology of photocured samples was characterized by Scanning Electron Microscopy and the size distribution of droplets was assessed and correlated to the curing conditions. The photopolymerization was implemented according to the Polymerization Induced Phase Separation method under radiation curing and monitored by FTIR spectroscopy via conversion of the thiol-ene bond S-H at 2570 cm-1 and the allylic C=C bond at 1647 cm-1. The observed monomer conversion was monitored and analyzed in terms of the applied dose and the amount of diluent added to the thiol-ene formulation. Electro-optical properties were analyzed with UV-spectroscopy. A shift in the reflectivity curve versus wavelength was found under electric activation. The liquid crystal birefringence was obtained from the wavelength at the peaks of oscillations and changes were calculated in terms of the strength of the applied field. Hysteresis and memory effects were evidenced and discussed.

 

 

Keywords:  FT-IR, nanocomposites, morphology, reflectivity.

 

 

 

 


* To whom correspondence should be addressed

University Aboubakr Belkaid, Faculty of Sciences, Department of Physics, Tlemcen BP119, Algeria.

Email: red_benmouna@mail.univ-tlemcen.dz

Mobil.  +213 70 96 03 54; Fax. +213 43 28 64 80