Biphasic polymerization processes and ethylene-based polyolefins therefrom

A method for preparing ethylene-based polyolefin, the method comprising:

• (i) providing a polymerization vessel;
• (ii) continuously charging the polymerization vessel with monomer including ethylene and olefin monomer copolymerizable with ethylene, a solvent, and a single-site catalyst system, to thereby form a polymerization mixture;
• (iii) maintaining the polymerization mixture within the vessel at a temperature at or above the lower critical phase separation temperature of the polymerization mixture;
• (iv) mixing the polymerization mixture within the vessel so that the temperature, pressure, and concentration of the polymerization mixture within the vessel is substantially uniform;
• and
• (v) continuously removing monomer, polymer formed by the polymerization of monomer, solvent, and single-site site catalyst system from the polymerization vessel at a rate substantially constant to the rate of continuously charging monomer, a solvent, and a single-site catalyst system, where the polymer continuously removed from the polymerization mixture is ethylene-based polyolefin having a molecular weight distribution of less than 2.30.