| The experimental research program that forms the basis of this thesis has been directed towards the design, synthesis, processing and physical characterization of well-defined conjugated polymer networks. It attempts to provide answers to the questions how such materials can be synthesized and processed and how the introduction of cross-links can be exploited for the creation of polymeric materials with optimized optic and electronic characteristics. Interestingly, this family of materials has received little attention in the past, at least as far as systematic studies of well-defined systems are concerned. This situation may be a direct consequence of the challenge to introduce conjugated cross-links into conjugated polymers and retain adequate processibility.; We have shown that organometallic polymer networks based on linear conjugated polymers are readily accessible through ligand-exchange reactions. This approach was exemplified by exploiting the ethynyl moieties comprised in poly( p-phenylene ethynylene) (PPE) derivatives as ligand sites, which allow for complexation with selected metals and cross-linking via the resulting PPE-Metal complexes. Focusing on the dinuclear complex [Pt-(mu-Cl)Cl-PPE] 2 and PPE-Pt0 as crosslinks, we have conducted an in-depth investigation on how the nature of the metal cross-links influences the materials characteristics, in particular the charge transport properties. We first investigated the charge carrier mobility of poly[2,5-dioctyloxy-1,4-diethynyl-phenylene- alt-2,5-bis(2'-ethylhexyloxy)-1,4-phenylene] (EHO-OPPE), as a classic representative of poly(p-phenylene ethynylene) (PPE) derivatives, which represent an important class of conjugated polymers. In what appears to be the first study ever conducted on the mobility of any PPE, we found that EHO-OPPE displays ambipolar charge transport characteristics with very high electron (1.9·10-3 cm2V-1 s-1) and hole (1.6·10-3 cm 2V-1s-1) mobilities. Most importantly, the introduction of Pt0 cross-links was found to enhance the charge carrier mobility of the investigated systems by up to an order of magnitude. Electron and hole mobilities of the order of 1.5·10-2 cm2V-1 s-1 were measured for these materials, representing the highest mobilities ever reported for disordered conjugated polymers. More importantly, the study unequivocally proves that the introduction of conjugated cross-links indeed leads to a significant improvement of the carrier mobility of conjugated polymers. Work involving [Pt-(mu-Cl)Cl-PPE] 2 cross-links suggests that the nature of the metallic cross-links is exceedingly important.; In a second approach we have demonstrated that the processing issues associated with covalently cross-linked conjugated polymer networks can be readily overcome if these materials are synthesized in the form of cross-linked nanoparticles and processed as suspensions. In a series of ground-breaking experiments, we have shown that covalently cross-linked conjugated polymer particles can be produced by conducting cross-coupling reactions in aqueous emulsions instead of homogeneous solutions and using multifunctional cross-linkers. The size of the spherical polymer particles can easily be tuned over a wide range (mm to nm) by modification of the reaction conditions. The resulting materials can be processed in the form of suspension and promise interesting electronic properties. (Abstract shortened by UMI.)... |
