Synthesis and characterization of polymers with electroluminescent properties

Author(s)

Flávia Maria Marconi

• Document type: Master's Dissertation
• Press: São Carlos. , gráficos, ilustrações, tabelas.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2002-08-30

Examining board members

Debora Terezia Balogh; Tito Jose Bonagamba; Hans Viertler

• Advisor: Debora Terezia Balogh
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Indexed in: Banco de Dados Bibliográficos da USP-DEDALUS
• Location: Universidade de São Paulo. Biblioteca do Instituto de Física de São Carlos; Te1481

Abstract

In this work, three dialkoxy derivatives of poly(p-phenylenevinylene),which differs from each other by the size of the side chain, were synthesized and characterized: the poly(2-methoxy-5-hexyloxy-p-phenylenevinylene), MH-PPV, the poly(2-methoxy-5-dodecoxy-p-phenylene-vinylene), MD-PPV and the poly(2-methoxy- 5-hexadecoxi-p-phenylene-vinyleno), MHd-PPV. These polymers have electroluminescent properties and can be used in light emitting devices. The synthesis consists in three steps: synthesis of aromatic ether, bischloromethylation of the ether yielding the monomer, and polymerization. The major difference regarding the synthesis processes lies on the monomer synthesis. A larger excess of reagents and longer reaction times were necessary to obtain the MD-PPV and MHd-PPV than that used to obtain the MH-PPV. All the products of the two first steps were characterized mainly by FTIR and NMR (proton and carbon 13). The chemical structures of the polymers were confirmed by FTIR and the molar masses determined by characterized by Size Exclusion Chromatography, revealing a high polydispersity and values of mean mass molecular weight (Mw) around 105. The thermal analysis presented values of glass transition temperatures, Tg, and softening, Ts, above 100 oC, and decomposition temperatures above 400oC for the three polymers. The MHd-PPV, presented, besides the Tg, a transition in 50oC, which may be related to the melting of the side chain. Films of the three polymers prepared from different solvents presented different morphologies, as observed by Atomic Force Microsocopy, slightly different absorptions (500-520 nm) and emission (585-600 nm) maxima and different photo-degradation processes depending on the solvent used to prepare the films. Therefore, the different size of the side chain presented effects mainly on characteristics as thermal transitions and film morphologies, and, in consequence of the late, on the shape of the emission and on the degradation properties (AU)