Polymer flow index modifier

A method for modifying a polymer flow index, comprising:

• providing monomers to a polymerization reactor;
• providing a chromium catalyst to the polymerization reactor;
• and
• providing an active amount of a flow index modifier to the polymerization reactor, wherein the flow index modifier is carbon dioxide and is from 15.00 parts per million to 50.00 parts per million based upon the monomers and wherein providing the active amount of the flow index modifier forms a polymer having a density that is reduced as compared to a second polymer having a different density, where the second polymer is formed by a same polymerization process, but without utilizing the active amount of the flow index modifier.