Patent ID: 8193307

Claim:
A method for synthesizing a polymer for use in photoresist compositions, comprising: performing a polymerization reaction to form a polymerization product mixture comprising a polymer and subjecting the polymerization product mixture to molecular weight fractionation, wherein the molecular weight fractionation step is a liquid-liquid phase separation technique; wherein the liquid-liquid phase separation technique comprises two or more iteration steps wherein an iteration step (a) comprises: dissolving the polymerization product mixture in a good solvent (A), adding a poor solvent (A) to the good solvent (A) containing the polymerization product mixture, then forming a liquid poor solvent phase and a liquid polymer-containing phase, separating the liquid poor solvent phase (a) from the liquid polymer-containing phase (a), and then performing an iteration step (b) on the liquid polymer-containing phase, wherein the iteration step (b) comprises adding a good solvent (B) that is different from the good solvent (A) to the liquid polymer-containing phase and the good solvent (B) has a higher dissolving power of the polymer than the good solvent (A), adding a poor solvent (B) to the good solvent (B) containing the liquid polymer-containing phase, then forming a liquid poor solvent phase (b) and a liquid polymer-containing phase (b), and separating the liquid poor solvent phase (b) from the liquid polymer-containing phase (b).