US 9,256,127 B2  187  188  -continued  -continued  Monomer?  Monomer 8  Monomer9  (~)15  ✓  Fa  a  Polymer 1  C~b  ✓  Fa  >-b  ✓  a  (~)35  ✓  Fa  a  rb  (~)15  /  Fa  a  (~)10  /  Fa  a  Polymer 2  (~)55  /  Fa  ()Jo $^{(~)10 }$ (~)35  ✓  Fa  a  Polymer 3  Synthesis Example 2  Synthesis of Polymers  A series of polymers for use in resist compositions were  synthesized by dissolving selected monomers in propylene  glycol monomethyl ether acetate (PGMEA), copolymeriza› tion reaction, crystallizing from methanol, repeatedly wash› ing with methanol, isolation and drying. The composition of  a polymer was analyzed by $^{1}$H-NMR spectroscopy, and the  Mw and Mw/Mn determined by GPC. The polymers are  designated Resist Polymers  1  to 18 and Comparative Resist  Polymers  1  to 7.  Resist Polymer  1  Mw=S,500  Mw/Mn=l.67  Resist Polymer 3  Mw=S,300  Mw/Mn=l.67  Resist Polymer 2  Mw=S,400  Mw/Mn=l.65 