Table 4.
Composition of the respective free carboxyl groups of the studied polymers, respective structures and obtained Zetamax values.
| Polymers | % ionsable groups | pH Dissolution Threshold | Zetamax (mV) |
|---|---|---|---|
| HP-50[1] | 21–27% (phthalyl) | 5.0 | −14.69 ± 0.89 |
| HP-55[1] | 27–35% (phthalyl) | 5.5 | −19.75 ± 0.95 |
| HPMC AS-LF[2] | 14–18% (succinoyl) | 5.5 | −15.41 ± 1.22 |
| HPMC AS-HF[2] | 4–8% (succinoyl) | 6.8 | −8.76 ± 0.29 |
| EUDRAGIT L100[3] | 46–50% (methacrylic) | 6.0 | −29.88 ± 1.80 |
| EUDRAGIT S100[3] | 23–30% (methacrylic) | 7.0 | −27.73 ± 0.52 |
 | |||
A: Phthalyl group; B: Succinoyl groups; C: x = Methacrylic acid, y = Methyl Methacrylate. [1]: Shin-Etsu, 2002; [2]:Shin-Etsu, 2005; [3]: Evonik, 2012.