Smart membranes with pH-responsive control of macromolecule permeability

- Hybrid membranes are developed by coating the pores of AAO templates with polymers.
- Initiated chemical vapor deposition is used to conformally coat the walls of the pores.
- pH responsive polymers are coated to control the pore size of the membranes.
- Permeability of PAA and BSA molecules can be tuned by changing the pore size.
- Shape and charge of PAA and BSA molecules affect the permeation rates.

Utilization of membranes for separation of macromolecules has gained wide interest in the last decade, especially after the development of smart membranes with tunable properties for improved separation performance. In this work, we fabricated hybrid membranes with variable pore sizes that depend on the pH of the environment. Hybrid membranes were prepared by conformally coating the pore walls of anodic aluminum oxide (AAO) templates with the pH sensitive poly(methylacrylic acid-co-ethylene glycol dimethacrylate) (p(MAA-co-EGDMA)) polymer using initiated chemical vapor deposition (iCVD). Performance of the membranes was investigated under different pH conditions using nanoparticles, polyacrylic acid (PAA) and BSA protein as permeates. Reduced pore sizes at pH 9 due to swollen polymer decreased the permeability of permeates compared to that at pH 3. In addition to size, charge interactions between the polymer surface and permeates affected the permeation. At high pH values, permeation of BSA was reduced due to reduced pore size and the electrostatic interactions with the polymer.