Polymeric hydrogel thin film synthesis via diffusion through a porous membrane

• We report a simple bi-cell approach to synthesize polymer hydrogel thin films.
• A heterogeneous reaction occurs at the surface of a nanoporous filter membrane.
• No specialized instrumentation or intensive experimental steps are required.
• Applying functional crosslinkers confers stimuli-responsiveness to synthesized film.
• Exposure to glutathione and/or free amine groups degrades synthesized chitosan films.

We report here a simple, versatile bi-cell-based platform for preparing crosslinked polymeric hydrogel thin films. Briefly, a nanoporous membrane is used to separate two solutions: one containing crosslinking molecules and the other containing oligomers. The crosslinking molecule diffuses through the membrane and reacts with the oligomer to form a polymeric film at the surface of the nanopore membrane. In this paper, a proof-of-concept experiment is described using crosslinkers with imidoester moieties (dimethyl 3,3′-dithiobispropionimidate (DTBP) or dimethyl suberimidate (DMS)) and chitosan oligomers. Crosslinking with DTBP or DMS also conferred degradability to the chitosan film. The film formation was confirmed and its morphology examined with electron microscopy. The chitosan film degradation was quantified by monitoring the transport of gold nanoparticles through the chitosan film after a degradation treatment. The film synthesis method presented here can potentially be used to prepare functional hydrogel thin films for biosensors, coatings and drug delivery systems in an inexpensive, high-throughput manner.