Preparation Of Micro-and Nanoscale Composite Interfacial Structures Based On The Breath Figures Method

Breath figures (BF) method is a dynamic templating method for surface patterning of polymers and nanomaterials. The BF method represents a single-step technique for fabricating films with ordered microscale holes utilizing condensed water droplets as templates, which evaporate after they leave ordered imprints on the film surfaces. After the establishment of the BF methodology system, new research trends have been developed in recent years. Researches concerning the preparation of chemically heterogeneous patterns based on the BF method and structural/chemical secondary processing towards the original honeycomb-patterned structures have become two of the most representative research directions of the BF method. Based on that, this thesis explores to bring new insights into the two important subjects of the BF related study. Amphiphilic surfactant and solid particle were employed as second component to serve as stabilizers in the BF method and achieve assisted fabrication of honeycomb-structured structure. The directed interfacial assembly properties of the second component were also studied. Furthermore, based on the reverse honeycomb-structured substrate, secondary processings based on self-assembly methods were carried out to construct functional micro-and nanoscale hierarchical structures.1. Surfactant-assisted fabrication of honeycomb-structured films via the BF method. ---Amphiphilic surfactant PEO-PPO-PEO was introduced to assist the fabrication of ordered honeycomb structure porous film of poly(lactic acid) via the BF method. The surfactant was proved to be able to effectively stabilize the templating water droplets and achieve surface pattering of PLA film. Several influencing factors on pattern formation were investigated, such as atmosphere humidity, solution concentration, solution application quantity and the molecular weight of PLA. Since PEO is significantly resistant to protein adsorption, fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA) was used as probe to investigate the protein adsorption onto the patterned film. Fluorescence images showing corresponding honeycomb patterns indicating that functional protein-resistance patterning surface has been successfully obtained. The PEO constituent has been proved to show selective allocation within the interior walls of the pores and chemically heterogeneous pattern has been achieved.2. Particle-assisted fabrication of honeycomb-structured hybrid films via the BF method and directed interfacial assembly of particles into ordered arrays.-Particle-assisted fabrication of honeycomb-structured hybrid films was carried out by employing solid particles as stabilizers in the BF method. Such a procedure tested the possibility of the combination of Pickering emulsions and breath figures, which are two classical self-assembly processes. Regularly patterned porous polystyrene film with particles decorating the inside walls of the open pores can be readily prepared. Different assembling characteristics of the particles under different circumstances are also discussed. To further extend the application of such particle-assisted, bottom-up surface patterning technique to other kinds of particles, polymeric particles and microgels were employed to serve as stabilizers in BF method. As expected, all three kinds of particles, including solid inorganic, solid polymeric and microgel ones, succeeded in assisting in the formation of BF arrays in polymer films. The self-assembly of nanoparticles at the fluid/fluid interface (Pickering emulsions) in the BF method were also explored to direct nanoparticles onto BF microarrays. Circular rings of nanoparticle-decorated honeycomb-structured polymeric film can be obtained by a one-step process. The combination of Pickering emulsions and capillary flow in the BF method may be responsible for the formation of this intriguing structure.3. Secondary processings on the reverse honeycomb-structured substrate to construct functional micro-and nano-scale hierarchical structures. -Using the obtained BF porous film as molding substrate, we prepared poly(dimethylsiloxane) (PDMS) negative replica (reverse honeycomb-structured substrate) with arrays of island-like protuberances by means of soft lithography. Hierarchical superhydrophobic surfaces were successfully fabricated by introducing nano-scale roughness onto the reverse honeycomb-structured substrate. Chemical deposition of silver nanoparticles and layer-by-layer (LBL) assembly of silica nanoparticles were employed to achieve the introduction of nano-scale roughness. pH-amplified exponential growth LBL self-assembly process was performed on the reverse honeycomb-patterned substrate. Different morphological characteristics at different cycles of assembly were intensively studied. Guided by underlying hexagonally patterned islandlike arrays, the diffusive polyelectrolytes rapidly interweaved into linear, multilayered structures which were distributed along the grooves between the patterned protuberate and formed a regular network of multilayered film with uniform mesh size after four bilayers of assembly. While topographically asymmetric, free-standing, polyelectrolyte multilayer films were fabricated after performing more than eight bilayers of assembly. Superhydrophobic surfaces could be readily obtained after several bilayers of LBL assembly, indicating that successful fabrication of functional micro-and nanoscale hierarchical structures can be achieved. Both high-and low-adhesion superhydrophobic surfaces can be obtained with different bilayers of assembly, proving that different levels of nano-to microstructural hierarchy can be realized using this method.