One-step process to create porous structures in cross-linked polymer films via breath-figure formations during in situ cross-linking reactions

This work demonstrates a new strategy of producing honeycomb-like porous structures in cross-linked polymer films via a simple one-step synthesis/fabrication process. This is based on the “breath figure” formation during the in situ cross-linking of reactive monomer solutions. A chloroform solution, containing tert-butyl acrylate monomer and tetraethylene glycol dimethacrylate cross-linker, was cross-linked upon UV radiation under a moist and nitrogen saturated chamber. Micron-sized pores with reasonable uniformity were obtained in the cross-linked polymer films. The size, shape, uniformity and ordering of the pores show significant dependences on the processing conditions. Using this method, porous structures were also achieved in a commercially available photo-active resin, NOA 65, illustrating the generality of this approach.