43  US 9,152,050 B2  44  Herein R $^{21 }$is each independently hydrogen or methyl, V1, V and V$^{5 }$each are a single bond or ----C(=O)-O-R 23  -, V 3  and V$^{4 }$each are -C(=O)-O-R  24 -, R  $^{23 }$and R $^{24 }$each are  a single bond or a straight, branched or cyclic C$_{1 }$-C$_{10 }$alkylene  group which may contain an ether or ester moiety, R $^{22 }$is each  independently hydrogen, or a C$_{1 }$-C$_{4 }$ straight or branched  alkyl, alkoxy, cyano, alkoxycarbonyl, acyloxy or acyl group,  W$^{1 }$and W$^{2 }$each are methylene or ethylene, W$^{3 }$is methylene,  oxygen or sulfur, W 4  and W$^{5 }$each are CH or nitrogen, and s  and t each are 1 or 2.  Examples of the monomers from which the recurring units  (cl) to ( c9) having a phenolic hydroxyl group are derived are  given below.  -continued  0  0  OH  0  HO  OH  :x)  ~-- I  h’{  HO  OH  ~o  t1J-o’  OH  -continued  X  bo  Q  ~ $_{OH }$ HO  OH 