In collaboration with Nippon Paul, we have purified P(St-b-2VP), a high-chi DSA, and analyzed its metal composition (Figure 37). （The polymer was synthesized by us (Figure 36), and its molecular weight and composition were Mw=7930 (MALS), PDI (GPC) = 1.07, and St : 2VP = 1:1.
Metal concentration in P(St-b-2VP)/PGMEA solution before and after single step filtration.
The Na and Li metals were drastically reduced after a single pass through a 5 nm Nylon 66 filter. (Figure 37) The final metal impurity content is shown in Summary.
