Class II Polycondensations

To the best knowledge of the author, non-stoichiometric polycondensations of this class have not been studied yet, A recently published speculative discussion[12] of suitable monomer combinations should not be repeated in this book. 

Presumably, the oldest non-stoichiometric polycondensation of class III is a synthesis poly(phenylene sulfide), PPS, which was patented in 1967 by Edmonds and Hill [25]. The first(nonintended) synthesis of low molar mass PPs was found by 

Friedel [26] in 1888 by heating benzene and elemental sulfur in the presence of AICI3. A few years later Genvress published a more detailed study of this reaction [27]. Fifty years after Friedels publication McCallum described a more convenient laboratory method [28], namely, a polymerization of 1,4-dichlorobenzene with elemental sulfur and potassium carbonate. Lenz and other members of Dow Chem [29-31] tried to the problems of the McCallum method (branching and cross-linking), but a satisfactory procedure, suitable for a technical production of PPS was not found. However, heating of 1,4-dichlorobenzene with sodium sulhde in NMP as described by Edmonds and HiU yielded linear PPS. With addition of certain metal carboxylates as catalysts molar masses around 35 kDa were achieved [32]. Further variations of this approach were reported by other authors [33]. Based on this method Phillips Petroleum elaborated a technical production and commercialized PPS under the trade mark Ryton . 

From the preparative point of view it should be noted that Hay et al. prepared polyformals for more than 15 bisphenols. Fluorine substituted polyformals were later contributed by a Japanese research group [47]. Those authors observed the 

In 1999 Endo et al. [49] reported on the polycondensation of bisphenol-A with 2,2-dichloro-l,3-benzobisoxazole (see. Formulas 8.6). Again a two-step kinetic 

---