Para‐Xylylenes and analogues by base‐induced elimination from 1,4‐bis‐(dialkylsulfoniomethyl)arene salts in poly(1,4‐arylene vinylene) synthesis by the wessling soluble precursor method

Abstract

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 (Mw = 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. © 1992 John Wiley & Sons, Inc.

The Gilch Synthesis of Poly(p‐phenylene vinylenes): Mechanistic Knowledge in the Service of Advanced Materials

“…Wessling postulated a radical mechanism, possibly initiated by dimeric diradicals VI (Scheme 2). [26] In contrast, Lahti et al, [113] Garay and Lenz, [114] and Hsieh [115] reported results that pointed toward anionic chain growth, while Hall and co-workers [116] and, later, Lahti and co-workers [117,118] realized that polymerization also proceeds in acidic media but is suppressed when 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) is added as a scavenger. Also Cho et al, who first favored anionic chain growth, [119] revised his earlier standpoint and has favored radical chain growth since then.…”

Photoinduced Gilch Polymerization: A Basically New Access to Poly(p-phenylene vinylenes) (PPVs) of Exciting Constitutional Homogeneity

“…Also, satisfying purity of the products is a challenging issue. Chain‐growth processes on the other hand, such as Wessling, sulfinyl, xanthate and Gilch reactions, give high‐molecular‐weight products, but the chains contain characteristic defects . Impurities, constitutional defects and insufficient molar masses are not tolerable, however, as they downgrade device performance.…”

A Unique Processable Green Polymer with a Transmissive Oxidized State for Realization of Potential RGB‐Based Electrochromic Device Applications

“…Since that time, a number of methodologies have been developed to overcome this significant drawback. Most common and effective strategies were the synthesis of soluble precursors that form a conductive coating upon heat treatment [6] and the introduction of alkyl side chains [7] in the polymer structures. It has clearly been demonstrated that alkyl side chains not only enhance the ease of processing, but also modify the electronic properties of the conjugated polymers.…”