Abstract
As an efficient technique for the preparation of polymeric hexagonal orderly arrays, the breath figure (BF) process has opened a modern avenue for a bottom-up fabrication method for more than two decades. Through the use of the water vapor condensation on the solution surface, the water droplets will hexagonally pack into ordered arrays, acting as a template for controlling the regular micro patterns of polymeric films. Comparing to the top-down techniques, such as lithography or chemical etching, the use of water vapor as the template provides a simple fabrication process with sustainability. However, using highly hazardous solvents such as chloroform, carbon disulfide (CS2), benzene, dichloromethane, etc., to dissolve polymers might hinder the development toward green processes based on this technique. In this review, we will touch upon the contemporary techniques of the BF process, including its up-to-date applications first. More importantly, the search of greener processes along with less hazardous solvents for the possibility of a more sustainable BF process is the focal point of this review.
Highlights
Breath figure (BF) is an example of the nature phenomenon of the formation of water droplets on surfaces (Figure 1)
The interfacial properties between the water droplets and the solvent would mainly influence the morphology of honeycomb-like films
The formation of inner porosity for poly(ε-caprolactone) (PCL) was obtained via the supercritical CO2 (SCCO2) technique, whereas the outer porosity was produced via the BF process
Summary
Breath figure (BF) is an example of the nature phenomenon of the formation of water droplets on surfaces (Figure 1). Since the first discovery in 1911 [1,2], for morphology observation, and further development by Francois et al [3] in 1994 for materials science, the BF process has become one of the most promising fabrication methods in the production of porous polymeric films with ordered arrays. A record high-power conversion hazardous solvents such as chloroform, carbon disulfide (CS2 ), dichloromethane, or benzene for dissolving polymers would stand in the way of the development of a greener BF process. In order to reduce the environmental impact, green chemical processes and synthesis design are strenuously developed for improving chemical ingredient manufacturing, nanotechnology, flow chemistry, and process intensification under harsh synthesis conditions [6]. A summary and an outlook on this greener BF process are presented at the end of this review
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