Polymerization Macallum

The Macallum polymerization (6, 7, 8) for preparing poly(arylene polysulfides) has been shown by Lenz and co-workers (9) to involve a combination of free-radical and nucleophilic substitutions. This polymerization involves the reaction of a polyhaloaromatic compound with an alkali-metal sulfide or an alkaline-earth metal sulfide catalyzed by sulfur and carried out at a high temperature without solvent. Related to the Macallum reaction are two nucleophilic processes for the preparation of poly(phenylene sulfide). One of these, reported by Lenz and co-workers (10, 11), involves heating cuprous or sodium p-bromothio-phenoxide at 250° to 305°C ... 

Lenz and Carrington [11 If] reinvestigated the Macallum polymerization and extended our polymerization data on these systems. Some typical polymerizations are shown in Table XI. 

In 1954 Gow Chemical Company purchased the Macallum patents because they made p-dichlorobenzene and had an interest in thermally stable plastics. (2) The Dow workers made a detailed stu< of the Macallum polymerization system, (l) and the structure of the polymers. (8) They found that the process would be... 

These results indicate that the role of sodium carbonate in the Macallum polymerization probably is to accept acid and not to generate sodium sulfide.The preponderence of evidence indicates that the Macallum polymer is an insoluble, crosslinked non-crystalline polymer that contains too much sulfur to be PPS. 

Macallum reported that polymers prepared in this manner generally contained more than one sulfur atom per repeat unit (x in the range 1.0-1.3) (2). In addition the polymerization reaction was highly exothermic and difficult to control even on a small scale (3). Later Lenz and co-workers at Dow reported another synthesis of PPS (4,5,6) based on a nucleophilic substitution reaction involving the self-condensation of materials such as copper p-bromothiophenoxide. The reaction was carried out at 200-250°C under nitrogen in the solid state or in the presence of a reaction medium such as pyridine. It was quite difficult to remove the by-product, copper bromide, from polymers made by this process (7). These and other methods of polymerization have been reviewed by Smith (8). Polyphenylene sulfide resins have been described more recently by Short and Hill (9). 

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