Enhancing the Scalability of Crystallization-Driven Self-Assembly Using Flow Reactors

Abstract

Anisotropic materials have garnered significant attention due to their potential applications in cargo delivery, surface modification, and composite reinforcement. Crystallization-driven self-assembly (CDSA) is a practical way to access anisotropic structures, such as 2D platelets. Living CDSA, where platelets are formed by using seed particles, allows the platelet size to be well controlled. Nonetheless, the current method of platelet preparation is restricted to low concentrations and small scales, resulting in inefficient production, which hampers its potential for commercial applications. To address this limitation, continuous flow reactors were employed to improve the production efficiency. Flow platforms ensure consistent product quality by maintaining the same parameters throughout the process, circumventing batch-to-batch variations and discrepancies observed during scale-up. In this study, we present the first demonstration of living CDSA performed within flow reactors. A continuous flow system was established, and the epitaxial growth of platelets was initially conducted to study the influence of flow parameters such as temperature, residence time, and flow rate on the morphology of platelets. Comparison of different epitaxial growth manners of seeds and platelets was made when using seeds to perform living CDSA. Size-controllable platelets from seeds can be obtained from a series flow system by easily tuning flow rates. Additionally, uniform platelets were continuously collected, exhibiting improved size and dispersity compared to those obtained in batch reactions.

Figure 1

(a) TEM image of original platelets. (b) Illustration of flow setup for epitaxial growth of platelets. TEM images of platelets epitaxially grow at (c) 19 °C, (d) 25 °C, and (e) 30 °C. Platelet samples were not stained. Scale bars = 2 μm. Statistical value distribution of (f) length, (g) width, and (h) area.

Figure 2

TEM images of platelets epitaxially grow at (a) 100 μL·min^–1, (b) 200 μL·min^–1, (c) 400 μL·min^–1, and (d) 800 μL·min^–1. Statistical value distributions of (e) length, (f) width, and (g) area.

Figure 3

TEM images of flow extended platelets prepared at seed/unimer ratios of (a) 1:22.5, (b) 1:35, (c) 1:60, and (d) 1:110. Statistical comparison of platelets from flow and batch: (e) area, (f) length, and (g) width.

Figure 4

(a) TEM image of seeds. Sample was stained by uranyl acetate solution (1 wt %). (b) Illustration of flow setup for epitaxial growth of platelets. TEM images of flow platelets grown from seeds prepared at seed/unimer ratio of (c) 1:5, (d) 1:10, (e) 1:20, and (f) 1:30. (g) Area of flow platelets in comparison to the batch standards (red line). (h) Comparison of statistical size parameters of platelets prepared in different methods. Seed/unimer ratio is 1:10.