Fabrication of Macroporous Films with Closed Honeycomb-Like Pores from Exponentially Growing Layer-by-Layer Assembled Polyelectrolyte Multilayers

We report an innovative method for the fabrication of macroporous films with closed honeycomb-like pores of several micrometers by post-treatment of micrometer-thick poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) films. The precursor PAA/PAH films are fabricated by exponential layer-by-layer assembly of PAA and PAH, which produces PAA/PAH films with highly interpenetrated structures. We disclose that the high mobility of PAA and PAH, which originates from the highly interpenetrated film structures, allows a large-scale phase separation to take place upon post-treatment to produce micrometer-sized honeycomb pores. These macroporous PAA/PAH films can be conveniently released from substrates to produce free-standing films with satisfactory mechanical stability.