US 2020/0133122 Al  89  Apr. 30, 2020  -continued  OH  OH  [0128]  Of the recurring units having formula (b), those  units having a lactone ring as the polar group are most  preferred.  [0129]  The polymer may further comprise recurring units  of at least one type selected from recurring units having the  formulae (cl) to (c3).  [0130]  In formulae (cl) to (c3),  RA  is as defined above.  Z 1  is a single bond, phenylene,  ---O-Z 11 -,  ----C(=O)-O› Z11- or----C(=O)-NH-Z 11 -, wherein Z 11  is a C$_{1}$-C$_{20 }$ alkanediyl group, C$_{2}$-C$_{20 }$ alkenediyl group or phenylene  group, which may contain a carbonyl moiety (-CO-),  ester bond (-COO-), ether bond (---0-) or hydroxyl  moiety. Z 2  is a single bond or -Z$^{21}$-C(=O)-O› wherein Z$^{21 }$is a C$_{1 }$-C$_{20 }$divalent hydrocarbon group which  may contain a heteroatom. Z 3  is a single bond, methylene,  ethylene, phenylene, fluorinated phenylene, ---O-Z 31 -,  ----C(=O)---0-Z$^{31}$-or-C(=O)-NH-Z 31 -, wherein  Z$^{31 }$is a C$_{1 }$-C$_{6 }$ alkanediyl group, C$_{2}$-C$_{6 }$ alkenediyl group or  phenylene group, which may contain a carbonyl moiety,  ester bond, ether bond or hydroxyl moiety.  [0131]  In formula (cl), R 21  and R 22  are each indepen› dently a C$_{1 }$-C$_{20 }$monovalent hydrocarbon group which may  contain a heteroatom. R 21  and R 22  may bond together to  form a ring with the sulfur atom to which they are attached.  [0132]  Examples of the monovalent hydrocarbon group  represented by R 21  and R 22  include alkyl groups such as  methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, cyclo› propyl,  cyclopentyl,  cyclohexyl,  cyclopropylmethyl,  4-methylcyclohexyl, cyclohexylmethyl, norbomyl, and ada› mantyl, alkenyl groups such as vinyl, ally!, propenyl, bute› nyl, hexenyl, and cyclohexenyl, aryl groups such as phenyl,  naphthyl, and thienyl, and aralkyl groups such as benzyl,  1-phenylethyl and 2-phenylethyl. Inter alia, aryl groups are  preferred. In these hydrocarbon groups, some hydrogen may  be substituted by a moiety containing a heteroatom such as  oxygen, sulfur, nitrogen or halogen, and a moiety containing  a heteroatom such as oxygen, sulfur or nitrogen may inter› vene between carbon atoms, so that the group may contain  a hydroxyl moiety, cyano moiety, carbonyl moiety, ether  bond, ester bond, sulfonic acid ester bond, carbonate bond,  lactone ring, sultone ring, carboxylic anhydride or haloalkyl  moiety.  [0133]  In formula (cl),  M- is a non-nucleophilic counter  ion. Examples of the non-nucleophilic counter ion include  (cl)  ~>  {A  H  Z 1  I  R21_ 8 +_R22  M- (c2)  (c3) 