Polyethylene oxide (PEO) (View the MathML sourceM̅m = 1000,000 g/mol), pentaerythritol tetraacrylate (PETRA), hexylacrylate (HA), and dichloromethane (DCM) were purchased from Sigma-Aldrich, (Dorset, UK). All materials were used as received. Distilled water (Triple Red, Long Credon, UK) was used for dissolving PEO and swelling of PEO cross-linked films. Unmedicated PEO hydrogel films were synthesized via UV crosslinking with varying concentrations of multifunctional monomer pentaerythritol tetra-acrylate (PETRA) as cross-linking agent, as explained in