Aug.  27,  2020  103  US 2020/0272048 Al  -continued  XR"  xR•  0  0  0  0  oy  0  0  0  RI!  0/  0  0  RA  00  /4#  0  0  0  I  RI!  [0084]  Examples of the monomer  from which the recur- ring units (a2) are derived  are shown below, but not  limited  thereto.  RA  and R$^{12 }$are as defined above.  RA  RA  Rl20  OR12  OR12  RA  R"ob$^{0 }$ OR12  RA  RA  R"O’O  F  OR12  -continued  RA  RA  )yo  0  Rl20  F  OR12  RA  RA  )yo  )yo  0  0  4  OR12  OR12  )yo  RA  )yo  0  ::to  ¢  OR12  OR12  RA  )yo  0  ~  0  0  OR12 