The most efficient synthetic approach towards high molecular weight PPVs is the Gilch (precursor-) route. Treating α,α′-dibromo-p-xylenes with a strong base initiates a cascade of reactions leading to the conjugated PPVs. The complexity of this reaction network may well be the reason for the often encountered and undesired batch-to-batch variations in opto-electrical performance. Schwalm et al. studied the Gilch polymerization using 1H-NMR spectroscopy and qualitatively indicated the species involved in the various reaction steps. Unfortunately, this study did not provide quantitative kinetic information.[1, 2] We investigated the reaction cascade of poly(2,5-bis-(2′-ethylhexyl)-1,4-phenylene-vinylene) (BEH-PPV) using time-resolved 1H-NMR spectroscopy and developed an extended fitting model describing the kinetics of all individual reaction steps in the synthesis of BEH-PPV (see Figure 1). By fitting this model to our experimental data we not only derived rate constants for monomer consumption and polymerization, but also for the final elimination step towards the conjugated end product. We extended our study by investigating the influence of UV-light on the initiation process of the polymerization. Despite the fact that the Gilch polymerization has been known for some time, only limited and purely qualitative information is available concerning the influence of UV-irridation.[3] For this reason, we investigated this system using in situ UV-irradiation NMR-spectroscopy to gain information at any time during illumination and to retrieve quantitative kinetic data.[4]

Mechanistic investigation and kinetic modeling of PPV polymerization via Gilch using time-resolved low temperature and in situ UV-irradiation NMR-spectroscopy

253rd National Meeting (2017)

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