Table 4. Lower and Upper Contact Angles (CA), Their Differences (Δ), and Transition Temperatures Tc Determined for POEGMA188, P(OEGMA188-Co-AAm), and PAAm after Immersion in Various pH Buffer Solutionsa.
| sample | buffer solution | lower CA [°] | upper CA [°] | Δ [°] | Tc [°C] |
|---|---|---|---|---|---|
| POEGMA188 | water | 52.0 ± 0.5 | 69.7 ± 0.7 | 17.7 | 22.1 ± 0.4 |
| pH = 3 | 45.4 ± 2.7 | 58.1 ± 0.5 | 12.7 | 9.6 ± 1.0 | |
| pH = 5 | 48.2 ± 2.2 | 56.0 ± 0.4 | 7.8 | 10.7 ± 1.0 | |
| pH = 7 | 51.0 ± 0.6 | 58.5 ± 0.3 | 7.5 | 17.5 ± 0.9 | |
| pH = 9 | 46.5 ± 0.3 | 56.9 ± 0.7 | 10.4 | 16.3 ± 0.5 | |
| P(OEGMA188-co-AAm)2 | water | 56.6 ± 1.3 | 67.6 ± 1.0 | 11.0 | 19.3 ± 1.7 |
| pH = 3 | 45.7 ± 0.3 | 54.4 ± 0.2 | 8.7 | 12.3 ± 0.3 | |
| pH = 5 | 47.8 ± 0.4 | 58.6 ± 0.4 | 10.8 | 16.0 ± 0.6 | |
| pH = 7 | 43.4 ± 0.5 | 50.1 ± 0.3 | 6.7 | 16.9 ± 0.7 | |
| pH = 9 | 46.4 ± 0.5 | 59.4 ± 0.5 | 13 | 16.2 ± 0.9 | |
| P(OEGMA188-co-AAm)5 | water | 8.8 ± 4.7 | 53.5 ± 3.1 | 44.7 | 15.1 ± 1.2 |
| pH = 3 | LCST-like at 14.2 °C and UCST-like at 23.0 °C | ||||
| pH = 5 | 36.6 ± 0.3 | 42.1 ± 0.2 | 5.5 | 13.5 ± 0.7 | |
| pH = 7 | 33.8 ± 0.7 | 44.8 ± 0.5 | 11 | 15.0 ± 0.6 | |
| pH = 9 | no temperature-induced transition | ||||
| PAAm | water | 11.7 ± 2.5 | 28.7 ± 0.6 | 17.0 | 10.6 ± 1.3 |
| pH = 3 | 18.5 ± 1.7 | 31.6 ± 0.6 | 13.1 | 11.8 ± 1.2 | |
| pH = 5 | 19.1 ± 2.8 | 27.4 ± 0.7 | 8.3 | 8.2 ± 2.5 | |
| pH = 7 | 17.7 ± 0.6 | 33.6 ± 0.5 | 15.9 | 9.9 ± 0.6 | |
| pH = 9 | 19.4 ± 1.1 | 33.4 ± 0.7 | 14 | 9.3 ± 0.7 | |
a
The numbers n denote the synthesized batches of P(OEGMA-co-AAm)n.