M. Mbarek

Theoretical study of the alkoxyls groups effect on PPV-ether excited states, a relationship with femtosecond decay

Based on Density Functional Theory (DFT), the effect of alkoxyl substituents groups on the excited states of new PPV derivative (PPV-ether) are studied. Thus differences on the relaxation energy, the atomic charge distribution and the conjugation length at their excited state are interpreted on the pathways of the nature on the emissive species. Photoluminescence and optical spectra of the corresponding modeling structures are carried out. Furthermore, the life time at the excited state are emphasized either theoretically from oscillator strength or experimentally from time resolved photoluminescence.

New polymer-matrix nanocomposites based on SWCNTs and PVK-PPV copolymer: Synthesis, functionalization and characterization

An original nanocomposite material was prepared by in-situ grafting of a PVK-PPV copolymer onto SWCNTs. The new composites were elaborated with various SWCNTs weight concentrations into homemade PVK-PPV copolymer. Different experimental analyses were performed to investigate their morphological features and their optical and vibrational spectroscopy behaviors as a function of the concentration of carbon nanotubes. Π-staking and covalent interactions and functionalization process between copolymer and SWCNT undergo dramatic effect in vibrational and photoemissives properties of copolymer matrix. Transmission (TEM) and scanning electron microscopy (SEM) were used. Then, resonant Raman scattering and steady-state and time-resolved photoluminescence (PL) and (TRPL) measurements were used to study the evolution of the spectroscopic characteristics and optical properties of PVK-PPV/SWCNTs composites. As results, we have observed PL quenching effect and a decrease of average life time. These indicated the processing of a charge transfer that leads to exciton dissociations to the SWCNTs matrix. Such results, also supported by modelling based on DFT method, have given a strong evidence of the functionalization and the charge transfer between the SWCNTs and the PVK-PPV copolymer and predicted a structure-properties correlation.