Fabrication And Application Of Hierarchically Porous Polymer Films Templated By Water Droplets

As a new self-assembly technique, water droplet templating (also called breath figure) has attracted increasing interest. It has been successfully used to fabricate micro, nanostructured porous films, which have wide applications in sensor, optical, biological technology. However, it is still a great challenge to construct hierarchically porous films templated by water droplets in a simpler and more efficient way.The present thesis reported controlled fabrication of polystyrene (PS) and polyvinylpyrrolidone (PVP) hierarchically porous films and explored their application as the structured template for replication.Here PS and PVP were two components and dissolved in chloroform. And hierarchically porous polymer films were fabricated in a high humidity when chloroform was evaporated and the water vapor was cooled to the formation of water droplets on the surface. The influence of experimental parameters such as polymer concentration, temperature, humidity and the weight ratio of PS/PVP was investigated on microstructures of the pores. Optical microscopy, scanning electron microscopy and atomic force microscopy were used to study the surface morphology of hierarchically porous polymer film. It was found that islandlike microstructures of PVP were located in the center of the pores, which can be removed by water. The extruded height of the islandlike microstructures can be manipulated by heating temperatures and heating time.The above-prepared porous films were printed by a patterned PDMS stamp under different heating temperatures. The contacted and non-contacted parts of porous films with the stamp had different height of PVP islands. Meanwhile, the functional components were successfully transferred to porous films during the microcontact printing. The porous films were further explored to apply as the structured templates to fabricate PDMS stamps. The simple post–treatment of as-prepared porous films with water washing, heating and embossing can result in well-defined replications with versatile and controlled microstructures.