Method of polyarylene sulfide crystallization

A method for forming a semi-crystalline polyarylene sulfide comprising:

• polymerizing a first sulfur-containing monomer and a first dihaloaromatic monomer in an organic amide solvent to form a polyarylene sulfide prepolymer;
• polymerizing the polyarylene sulfide prepolymer with a second dihaloaromatic monomer and a second sulfur-containing monomer;
• combining the polyarylene sulfide with a crystallization solution to form a polymer mixture, the mixture including the crystallization solution in an amount of about 5 wt.% or greater by weight of the mixture, wherein the crystallization solution is pre-heated prior to combination with the polyarylene sulfide, the polymer mixture being at a temperature of about 230° C. or greater upon formation;
• and
• cooling the polymer mixture at a rate of about 0.5° C. per minute or less until the polymer mixture reaches a temperature of about 190° C. or less, the polyarylene sulfide crystallizing during the cooling to form the semi-crystalline polyarylene sulfide.