In the preparation of polyphenylene sulfide from dichlorobenzene and sodium sulfide in a polar solvent, the use of an alkali metal carboxylate as polymerization modifier permits the production of a high molecular weight, soluble resin directly by polymerization. A separate curing or cross-linking step is eliminated from the usual process for producing injection molding resins. Molded specimens exhibit better tensile strength, elongation, impact strength, and resistance to cracking in thick sections than the more conventional resins produced by a combination of polymerization and curing processes. Fibers, films, and sheet exhibit a combination of good mechanical properties, chemical resistance, and thermal stability. © 1979, American Chemical Society. All rights reserved.