Evaporation-induced self-assembly films processed

Brinker et al. developed a simple evaporation-induced self-assembly (EISA) process that allows the rapid production of patterned porous or nanocomposite materials in the form of films, fibers, or spheres. Starting from a homogeneous solution of soluble silica and surfactant below the critical micellar concentration, evaporation of ethanol increased surfactant concentration, driving self-assembly of silica-surfactant micelles and their further organization. By... 

We were interested in the potential of the syndiesized diblock copolymers as templates in the synthesis of mesostructured silicate materials. Our focus was the pr aration of mesoordered thin films via the evaporation-induced self-assembly process [7]. For this purpose PDMS-b-PEO were mixed with a precursor solution containing the network-building species, and films were produced via a dip-coating procedure [8]. XRD diffraction patterns confirmed the formation of lamellar materials which were stable upon calcination at 430 °C/3 h. 

The tailored design of the titanium-coordinated surfactant and its application in an evaporation-induced self-assembly process followed by heat treatment enabled the preparation of periodic mesoporous silica-based films with a high loading and good dispersion of tetrahedral titanium atoms within the silica matrix. This approach is also feasible for a variety of other transition metal oxides. 

Several synthetic strategies to control the sizes of mesoporous nanoparticles have been reported. Lu[272] reported a rapid, aerosol-based process for synthesizing solid, well ordered spherical particles with stable pore mesostructures of hexagonal and cubic topology, as well as layered (vesicular) structures. This method relies on evaporation-induced interfacial self-assembly confined to spherical aerosol droplets. This simple, generalizable process can be modified for the formation of ordered mesostructured thin films. 

An important distinction to be made is that instead of being induced by spontaneous evaporation of solvent, the movement of the contact line will be controlled by the motion of the lower substrate, resulting in a programmable stick-slip motion in FESA. Therefore, ordered patterns (e.g., thin films, snipes and spokes) can be readily produced in a controllable manner. Notably, the transition between the different patterns may be observed by gradually tuning each variable individually (e.g., velocity of lower substrate). The influence of each variable on the evaporative self-assembly process can also be scrutinized separately. 

Another approach to the deposition of nanometre-sized particles on a surface has been described by Roth el a/. who thermally evaporated gold onto polystyrene in a vacuum chamber to form a thin film. Since the polymer-metal interaction is much weaker than the metal-metal interaction, the gold atoms form clusters in a self-assembly process. The gradient in cluster density was induced by using a blocking mask to shadow parts of the substrate. 

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