PARA-XYLYLENES AND ANALOGS BY BASE-INDUCED ELIMINATION FROM 1,4-BIS-(DIALKYLSULFONIOMETHYL)ARENE SALTS IN POLY(1,4-ARYLENE VINYLENE) SYNTHESIS BY THE WESSLING SOLUBLE PRECURSOR METHOD

para-Xylylenes are generated by-treatment of various 1,4-bis(dialkylsulfoniomethyl) arene dihalides with base in water, methanol, and aqueous acetonitrile, as shown by UV-Vis spectroscopy. This procedure allows the monitoring of the transient xylylene monomers that yield polyelectrolyte precursor polymers for poly (arylene vinylene)s, formed by variations of the chemistry developed originally by Wessling and co-workers. Alkoxy, alkyl, and halogen ring substituents on the sulfonium salt precursors do not greatly affect the ability to generate and observe the growth and decay of steady-state concentrations of the para-xylylene intermediates. Use of strong resonance-acceptor substituents-such as cyano or nitro-on the ring reduces production of a strong para-xylylene absorption, possibly due to reluctance of the ylides initially formed from the bis-sulfonium salts to eliminate to the xylylenes. By variation of UV-Vis conditions, it was found that use of 20% aqueous acetonitrile rather than water allowed formation of low to modest molecular weight polyelectrolytes in cyano-substituted cases (M(w) = 8000-37,000). Use of UV-Vis test experiments should be useful for screening of bis sulfonium salt precursors that may be expected to give high molecular weight polyelectrolytes-in cases where para-xylylene formation is easy-as well as for finding reaction conditions that will optimize polymer formation.