US 9,829,796 B2  171  172  RA!  RA!  ~  ~  )i-to  Q  oyo  0  RA!  ~  HO~O  0A 0  RA!  RA!  ~  ~  ~io  oA 0  o-{  0  RA!  ~  RA!  RA!  ~  RA!  ~  0  )=o  0  RA!  ~  It is also a particularly preferable aspect that a polar group  which the repeating unit (c) can have is an acidic group.  Preferable examples of the acidic group include a phenolic  hydroxyl group, a carboxylic acid group, a sulfonic acid  group, a fluorinated alcohol group (for example, a hexaflu› oroisopropanol group), a sulfonamide group, a sulfonyl  imide group,  a  (alkylsulfonyl)(alkylcarbonyl)methylene  group, a (alkylsulfonyl)(alkylcarbonyl)imide group, a bis  (alkylcarbonyl)methylene group, a bis(alkylcarbonyl)imide  group, a bis(alkylsulfonyl)methylene group, a bis(alkylsul› fonyl)imide group, a tris(alkylcarbonyl)methylene group,  and a tris(alkylsulfonyl)methylene group. Among these, the  -continued  -continued 