Feb.28,2019  67  US 2019/0064665 Al  to the flask over 4 hours. After the completion of dropwise  addition, the polymerization solution was continuously  stirred for 2 hours while maintaining the temperature of 80°  C. The polymerization solution was cooled to room tem› perature, whereupon it was added dropwise to 640 g of  methanol with vigorous stirring. The precipitate was col› lected by filtration, washed twice with 240 g of methanol,  and vacuum dried at 50°  C. for 20 hours, obtaining 36 g of  Polymer Pl in white powder form (yield 90%). On GPC  analysis, Polymer Pl had a Mw of 8,800 and a dispersity  Mw/Mn of 1.94.  [0313]  Synthesis of Polymers P2 to  PS  [0314]  Polymers P2 to  PS  were synthesized by the same  procedure as in Synthesis Example 1 aside from changing  the type and amount of monomers.  [0310]  Polymers for use in resist compositions were syn› thesized according to the following formulation.  [0311]  Synthesis of Polymer Pl  [0312]  In a flask under nitrogen atmosphere, 22 g of  1-t-butylcyclopentyl methacrylate, 17 g of 2-oxotetrahydro› furan-3-yl methacrylate, 0.48 g of dimethyl 2,2’-azobis(2- methylpropionate) (V-601 by Waka Pure Chemical Indus› tries, Ltd.), 0.41 g of 2-mercaptoethanol, and 50 g of MEK  were combined to form a monomer/initiator solution.  Another flask in nitrogen atmosphere was charged with 23  g of MEK, which was heated at 80°  C. with stirring. With  stirring, the monomer/initiator solution was added dropwise  Synthesis Example 1  [2] Synthesis of Polymers  Synthesis Examples 2 to 5  -continued  PAG-6  PAG-7  PAG-8  PAG-9  Polymer P2  Polymer P3  Mw  ~  8,400  Mw/Mn~ 1.83  r  0  0  {)  0  0  Polymer Pl  Mw~ 8,800  Mw/Mn~ 1.94 