M.Sc Thesis


M.Sc StudentAsaf Albo
SubjectNovel Guest-Host Nanocomposites: Conjugated Polymer/
Inorganic Layered Compounds
DepartmentDepartment of Materials Science and Engineering
Supervisor Full Professors Frey Gitti


Abstract

The optical and electrical properties of semiconducting light-emitting polymers are strongly affected by the polymer chain twists and bends, inter-chain interactions and defects. In our research, light-emitting polymers are confined into the galleries of an inorganic layered matrix to enforce polymer planarization, reduces inter-chain interactions and encapsulation. The intercalation of the light-emitting polymers into the layered compounds is done through Li intercalation, exfoliation and re-stacking in the presence of the polymer. The materials used in this study are polyfluorene and MoS2, giving the MoS2(polyfluorene) nano-composites. The synthesized host/guest nanocomposite materials are then characterized using x-ray diffraction (XRD), electron microscopy (SEM, HRSEM) optical absorption, Raman scattering, fluorescence spectroscopy and fluorescent microscopy. The nanocomposites are then processed into thin films for their later integration into light-emitting devices. The thermal and optical stability of the nanocomposite is also addressed with respect to those of the pristine polymer. More specifically, blue emitting polyfluorenes show degradation of the blue emission and a new broad green peak which increases with time, thermal treatments and UV exposure. The mechanism responsible for this phenomena and its relation to the aggregation of keto-deffects is currently discussed in the literature. The synthesized blue emitting nano-composite MoS2(polyfluorene), is a good system for investigating the degradation mechanism responsible for the green emission. The two dimensional confinement suppresses aggregation and hence de-couples the optical properties of planar polymer segments, from the optical properties of aggregates.