Table 2.
Contact angle values for as-made PAMs obtained in 0.3 M oxalic acid (type I and type II) and values for samples 1–5 after etching of the barrier layer (all of type I).
| Sample | Pore diameter (outer side) (nm) | Pore diameter (back side) (nm) | Thickness (μm) | Porosity, α (%) |
Contact angle (outer side), θ1 (degrees) | Contact angle (back side), θ2 (degrees) | Etch timea, t (min) |
| as-made (type I) | 44 | – | 65 | 17 | 80.14 | 93.97 | 0 |
| as-made (type III) | 25 | – | 75 | 28 | 30.01 | 82.08 | 0 |
| 1 | 64 | 63 | 65 | 33 | 82.78 | 43.04 | 15 |
| 2 | 70 | 69 | 38 | 39 | 100.97 | 64.99 | 20 |
| 3 | 75 | 76 | 52 | 45 | 115.15 | 96.28 | 35 |
| 4 | 54 | 39 | 26 | 23 | 98.67 | 81.07 | 10b |
| 5 | 50 | 60 | 45 | 20 | 63.64 | 31.15 | 15b |
aBilateral chemical etching of all substrates in 4% H3PO4 at 35 °C; bBack side physical etching in argon for 40 min in addition to bilateral chemical etching of the whole substrate.