Journal of Advanced Research in Science and Technology
Volume 6, Numéro 1, Pages 971-977

Thermal Study Of Photo-polymerization Reaction In The Preparation Of Composite Materials Based On Polymer

Authors : Hadjou Bélaid Zakia . Benkhaled Fatima Zohra . Beroguiaa Derouiche .

Abstract

Polymer Dispersed Liquid Crystals (PDLCs) were elaborated by polymerization induced phase separation under ultraviolet light (UV). A systems composed of Tripropyleneglycol diacrylate (TPGDA) monomer and a liquid crystal mixture (E7) were used as starting materials in the process of polymerization/cross-linking leading to a phase separation between polymer and liquid crystal. The time behaviour of the optical transmission of these films was experimentally studied during the period of exposure to UV-light in the absence of external applied fields. The transmission versus time curves of in-situ UV-cured TPGDA/E7 films reveal three regions: a first domain corresponding to a transparent film of the initial TPGDA/E7 mixture before exposure to UV light, a second time domain where the sample exhibits a fast relaxation process, just after the beginning of the UV irradiation of the monomer/LC blend, and an unusual third domain, characterised by an enhancement of the film transparency at longer relaxation times. This process depends on the sample preparation conditions and the film thickness. In this study, the temperature of the system (sample and two slats) was controlled before, during, and after the application of UV-light, with sample and without sample.

Keywords

Monomer ; liquid crystal ; ultraviolet irradiation ; phase separation ; polymerization/cross-linking