Abstract
Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in the foam phase preparation of porous polymeric microspheres. The introduction of a water-soluble organic solvent enables the control of polymeric microspheres’ internal structures, from porous to hollow. Because a water-soluble organic solvent is introduced, the organic solvent may be diffused toward the interface because of the affinity between the organic solvent and the oil droplets, resulting an accumulation of organic solvent molecules at the interface to form an organic solvent layer. The presence of this layer may decrease the evaporation rate of the internal organic solvent in an oil droplet, which extends the time for the mingling of porogen droplets to form a few large pores or even an extremely large single pore inside. This method is also capable of altering the thickness of hollow microspheres’ shells in a desired way, with improved efficiency, yield and the capacity for continuous use on an industrial scale.
Highlights
Polymeric microspheres with various internal structures have attracted increasing interest in modern science and technology due to their attractive characteristics, especially the usefulness of their inner spaces [1–5]
Polymeric microspheres were prepared in a foam phase
Without EtOH, PS microspheres were in possession of porous structures, as shown in Figure 1a, Without microspheres were in possession of porous structures, as shown in
Summary
Polymeric microspheres with various internal structures have attracted increasing interest in modern science and technology due to their attractive characteristics, especially the usefulness of their inner spaces [1–5]. Considerable effort has been made to control the internal structures of polymeric microspheres, including the utilization of microbubbles as templates [6,7] or the template removal method [8], emulsion solvent extraction [9], evaporation [10] and diffusion method [11], the self-assembly method [12,13] and the double emulsion method [14]. The reported methods are not versatile as it is not easy to control polymeric microspheres’ internal structures by using a particular method. A few papers have reported controlling microsphere structures, from the porous to the hollow, by decreasing the polymer concentration [10,15]. There is a need to develop a versatile method which can control the internal structures of polymeric microspheres. In our previous work [15], we demonstrated a time-saving method with a high yield for producing porous polymeric microspheres in a foam phase, which can be developed as a continuous
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