72  71  US 9,465,291 B2  -continued  (M-27)  (M-28)  flask (100 ml) was charged with 20 g of 2-butanone, purged  with nitrogen for 30 minutes, and heated to 80°  C. with  stirring. The monomer solution was added dropwise to the  flask over 3 hours using a dropping funnel. The monomers  were polymerized for 6 hours from the start of dropwise  addition of the monomer solution. After completion of  polymerization, the polymer solution was cooled with water  to 30°  C. or less. The cooled polymer solution was added to  400 g of methanol, and a precipitate (white powder) was  filtered off. The white powder was washed twice with 80 g  of methanol, filtered off, and dried at 50°  C. for 17 hours to  obtain a white powdery polymer (A-1) (15.2 g, yield: 76%).  The polymer (A-1) had an Mw of 7100 and a dispersity  (Mw/Mn) of 1.53. As a result of  $^{13}$C-NMR analysis, it was  found that the content of the structural unit  (I)  and the  content of the structural unit (VI) in the polymer (A-1) were  50.3 mo! % and 49.7 mo! %, respectively. The content of  low-molecular-weight components (i.e., components having  a molecular weight of less than 1000) in the polymer (A-1)  was 0.04 mass %.  A polymer was synthesized in the same mamier as in  Example 26, except that the types and the amounts of the  monomers were changed as shown in Table 1. The yield (% ),  the Mw, and the dispersity (Mw/Mn) of the resulting poly- mer are also shown in Table  1.  Note that "-" in Table 1  indicates that the corresponding component was not used.  8.56 g (50mol %) of the compound (M-1) and 11.44 g (50  mo!%) of the compound (M-27) were dissolved in 40 g of  2-butanone, and 0.85 g of AIBN (initiator) was dissolved in  the solution to prepare a monomer solution. A three-necked  TABLE 1  Monomer that produces  Monomer that produces  Monomer that produces  structural unit (I)  structural unit (II)  structural unit (VI)  Compo- Structural  Structural  Structural  nent  Amount unit content  Amount unit content  Amount unit content  [A]  Type  (mo!%)  (mo!%)  Type  (mo!%)  (mo!%)  Type (mo!%)  (mo!%)  Example 26  A-1  M-1  50  50.1  M-27  50  49.9  Example 27  A-2  M-2  50  50.1  M-27  50  49.9  Example 28  A-3  M-3  50  49.8  M-27  50  50.2  Example 29  A-4  M-4  50  50.0  M-27  50  50.0  Example 30  A-5  M-5  50  48.8  M-27  50  51.2  Example 31  A-6  M-6  50  48.6  M-27  50  51.4  Example 32  A-10  M-7  50  49.1  M-27  50  50.9  Example 33  A-11  M-8  50  48.1  M-27  50  51.9  Example 34  A-12  M-9  50  48.3  M-27  50  51.7  Example 35  A-13  M-10  50  49.1  M-27  50  50.9  Example 36  A-14  M-11  50  50.1  M-27  50  49.9  Example 37  A-15  M-12  50  50.1  M-27  50  49.9  Example 38  A-16  M-13  50  49.8  M-27  50  50.2  Example 39  A-17  M-14  50  50.0  M-27  50  50.0  Example 40  A-18  M-15  50  48.8  M-27  50  51.2  Example 41  A-19  M-16  50  48.7  M-27  50  51.3  Example 42  A-20  M-17  50  49.1  M-27  50  50.9  Example 43  A-21  M-18  50  48.8  M-27  50  51.2  Example 44  A-22  M-19  50  48.8  M-27  50  51.2  Example 45  A-23  M-20  50  48.3  M-27  50  51.7  Example 46  A-24  M-21  50  49.1  M-27  50  50.9  Example 47  A-25  M-22  50  48.8  M-27  50  51.2  Example 48  A-26  M-23  50  45.8  M-27  50  54.2  Example 49  A-27  M-24  50  48.3  M-27  50  51.7  Example 50  A-28  M-25  50  49.2  M-27  50  50.8  Example 51  A-29  M-9  30  29.8  M-27  55  55.3  M-10  15  14.9  Example 52  A-30  M-10  20  20.1  M-27  60  59.8  Example 53  A-31  M-6  70  69.9  M-28  30  30.1  Synthesis  a-1  M-27  73  54.1  Example 1  Examples 27 to 53 and Synthesis Example 1  Synthesis of Polymer [A]  Example 26 