One-pot fabrication of polymer micro/nano-discs via phase separation and a roll-to-roll coating process

Abstract

Disc-shaped particles are one of the unique and promising shapes that can improve adhesion to interfaces and can function as the key feature in various applications; e.g. injectable drug carriers. However, most of these methods include the shape deformation process from spheres to discs using various external stimuli or require multiple processing steps, which is complicated and has limitations in terms of continuous fabrication. We herein propose a novel method combining polymer blend phase separation and a roll-to-roll coating process to continuously fabricate polymer micro/nano-discs in a one-pot manner on a large-scale. The evaporation of solvent during a roll-to-roll coating process encourages the formation of homogenous island-like domains composed of the minor component dispersed in a matrix of the major component on a water-soluble polyvinyl alcohol (PVA) film. In fact, polyvinylpyrrolidone (PVP) was chosen as the major component since it dissolves in both water and chloroform. Another polymer, polystyrene (PS), as a minor component was dissolved in chloroform with PVP. A PVP and PVA matrix film can be easily washed out by water, and micro/nano-discs of the PS minor component can be obtained in a one-pot manner. This method is shown to be capable of continuously fabricating PS micro/nano-discs at a very high rate of ∼108 particles/min. The effects of fabrication conditions, such as the blend ratio and total polymer concentration on the dimensions of the PS discs were investigated, and a maximum aspect ratio (ratio between diameter and thickness) of 6.3 (diameter ∼830 nm, thickness ∼130 nm) was demonstrated. The method proposed in this study could provide a straightforward and time-saving way to continuously fabricate micro/nano-discs via polymer phase separation and a roll-to-roll coating process.