Low‐temperature synthesis of poly(p‐phenylenevinylene) by the sulfonium salt route

Abstract

Poly(p‐phenylenevinylene), PPV, is one of the most promising candidates among the conjugated polymers for use in all‐optical signal processing or as the active layer in light emitting diodes. Here, a low‐temperature route to PPV is reported which makes the synthesis compatible with many of the thermoplastic polymers used in microelectronics and optics. The applicability of this route to device fabrication is also addressed.

Progress with Light-Emitting Polymers

“…Research toward facilitating the elimination reaction at reduced temperatures has improved the process. For example, Müllen and co-workers demonstrated that through the use of sulfonium bromide salts, conversion to PPV can be initiated at temperatures as low as 100 C. [67] Other modifications of the Wessling chemistry directed toward improving film quality and performance include reports of precursors eliminating sulfinyl and sulfonyl groups rather than tetrahydrothiophene. [68±70] The need to convert precursor films to PPVs represents additional complexity to the processing of PLED devices and offers a variable that can significantly affect overall device power efficiency.…”

Influence from the sulfonate group () on the conversion process and emission efficiency of poly(p-phenylene vinylene)

“…5a). Therefore, the chemical structure and/or position of the -SO À 3 group of the substituent are important in lowering the temperature at which the leaving group in PTHT is released [18]. This is demonstrated here with linear molecules and sulfonic groups in the ends (CR and Tinopal), which facilitate thermal elimination of the lateral tetrahydrothiophenium group of PTHT.…”

“…On the other hand, the synthesis performed at lower temperatures may be disadvantageous as conversion of PTHT into PPV is only partial. Alternative PPV conversion processes were proposed initially by Garry et al [10] and Wu et al [11]. However, a major breakthrough for the processability of PPV was achieved by replacing the counter-ion C1 À in PTHT by a sulfonated compound, e.g.…”

Organic Light‐Emitting Diodes

“…These defects in the p-conjugated macromolecular chain shorten the effective conjugation length [140], act as quenching sites, and have been taken as responsible for the relatively low luminescence quantum efficiency of around 30% found for standard PPV [140,141]. It has been found that thermal elimination to PPV could be lowered to 115 C by using a bromide or a dodecylbenzenesulfonate (DBS) sulfonium salts instead of a chloride [142][143][144]. Other precursor routes have been taken for the synthesis of PPV, such as, those using sulfone and sulfoxide monomers, which allow polymerization in organic media and easier purifications of materials [145,146].…”