Physico-chemical, electrical and optical properties of regiorandom and regioregular MDMO-PPV

Abstract

Since the beginning of the nineties precursor routes towards semiconducting polymers are examined at the ‘Instituut voor Materiaal Onderzoek’ (IMO) part of the ‘Limburgs Universitair Centrum’ (LUC). Besides the successful development of a new synthetic precursor route, the so-called sulfinyl route, chemical and physical characterization techniques are used to better understand the structure-property relation. A widely used ‘workhorse’ conjugated polymer, MDMO-PPV (a PPV derivative) can be synthesized via this sulfinyl route. Two chemical defects related to asymmetrically substituted PPV-derivatives, such as the ‘workhorse’ material MDMO-PPV can be distinguished: defects related with the position of the side-chains (regioregularity) and defects related with interruptions of the conjugated system on the vinylene double bond (single bond defects). It is shown that the sulfinyl precursor route exhibits a versatile chemistry and can control both mentioned defects. This allows the preparation of a number of different batches of MDMO-PPV with various defect types and levels. In this context, some new basic scientific questions appear, namely: How to use these new synthetic possibilities to obtain high performance semiconducting organic polymers? What is the influence of regioregularity on the semiconductor properties? What is the influence of sp3 defects (single bond defects) in the conjugated chain on the semiconductor properties? The aim of this thesis is to clarify a relation between defects of MDMO-PPV and the performance of devices prepared with this material (structureproperty relation), via physical parameters. Beside the sulfinyl procedure to synthesize MDMO-PPV, a widely used synthetic procedure, namely the Gilch procedure is used as a reference in this work. ...