31  US 9,256,127 B2  32  -continued  (3)  ~  0  I  0  x’!.  1  A  ’oR4 +  Base or  M 0  xi  R2  R3  . )==o_  (6)  0  r-:1  ---(-ii)  __  _____  &o  (5)  45 Herein R  $^{1 }$is as defined above.  The monomer having formula ( 1) may be prepared accord› ing to the reaction scheme shown below although the synthe› sis route is not limited thereto.  -continued 