## 3 Result and Discussion
### Dissolution Method with a Water-Soluble Organic Solvent  
Although the three types of polymers, BL-01, BL-03, and BL-05 cannot be directly dissolved into aqueous solutions at all, the BL-02 can be dissolved in aqueous solution in spite of having a lower acid-value of 146, almost same as the three polymers. This is because BL-02 contains not only styrene but also the comparable number of butyl groups, possibly suppressing the fast agglomeration of the styrene block. This would suggest that those three polymers could be also dissolved in aqueous solutions when also efficiently eliminating or avoiding the fast agglomeration of styrene groups. Thus, we assumed that the three polymers could also be dissolved in the aqueous phase through alkaline neutralization, being slowly transferred from the dissolved state of the polymer in a water-soluble organic solvent. In this investigation, MEK and DEG were selected as the organic solvents and the solubilities of the polymers in them were evaluated at 28 wt% of the polymer concentration, which would be enough concentrated solution to finally prepare \(\sim\)0.1 wt% aqueous solutions of polymers, regardless of the aqueous solvent-polarity change. The results are summarized in Table 3. Polymers can be dissolved in MEK at room temperature and in DEG with heating, except for BL-04, which may be due to high acid-value which increases polarity and decreases the solubility in organic solvents. Regarding the solubility in DEG, BL-03 (soluble; 50 \({}^{\circ}\)C) would be higher than BL-05 (soluble; 90 \({}^{\circ}\)C), BL-05 would be higher than BL-01 (soluble; 110 \({}^{\circ}\)C) (Table 3). BL-03 would have higher solubility because its molecular weight is smaller than BL-05. The \(\alpha\)-MeSt in BL-03 and BL-05, which terminated the styrene polymerization, may be advantageous for solubility in DEG compared to DPE in BL-01. These results suggest the chemical structure between hydrophilic and hydrophobic domains and molecular weight would affect solubility in DEG. Subsequently, the small amounts of 28 wt% polymer solutions (BL-01, BL-02, BL-03, BL-05) in MEK and DEG were mixed with large amount of KOH aqueous solutions, where KOH molars were adjusted to be 1.2 times that of the carboxyl group in the polymers, and the final polymer concentrations were adjusted to be 0.1 wt%. As summarized in Table 4, in the case of the MEK solution, the alkaline aqueous solution became cloudy instantly, after mixing with the polymer solution; the polymers were not dissolved at all, even after treatment with ultrasonic waves for more than 1 h thereafter. In contrast, aqueous polymer solutions with transparency can be obtained from the polymer solutions in DEG. It should be noted that the polymers cannot be directly dissolved in the KOH solution containing 0.3 wt% DEG (Figure 3), which is the same solvent composition finally obtained when preparing 0.1 wt% polymer aqueous solution from the 28 wt% polymer solutions in DEG. Solubilities of BL-03 and BL-05 in alkaline aqueous solution were still poor, despite increasing the DEG compositions to 0.5 and 0.9 wt%, respectively, with the addition of ultrasonic wave for 1 h (Figure 3). From these results, DEG did not necessarily work, as changing the aqueous-solution nature, including the polarity, to dissolve polymers containing DEG in the aqueous solution is not important, but the process of dissolving polymers in DEG at first is important for preparing the aqueous polymer solutions; this well validates our assumed strategy for utilizing a pre-solution of polymers in a water-soluble organic solvent.