Photosensitive 2,5-distyrylpyrazine particles produced from rapid expansion of supercritical solutions

Precipitation of nanocomposite particles from a multi-component, rapidly expanding supercritical solution

“…The DSP monomer precipitates were polymerized by UV exposure (10-15 min) in the solid state for stabilization before imaging. The rounded shape of the DSP particles polymerized immediately after RESS suggests that these particles exhibit a lower degree of crystallinity than the original highly crystalline monomer material and this observation was confirmed by XRD measurements [31]. The amorphous state is a non-equilibrium condition for DSP and we have observed that the monomer particles recrystallize within approximately 2 weeks at standard temperature and pressure.…”

“…The amorphous state is a non-equilibrium condition for DSP and we have observed that the monomer particles recrystallize within approximately 2 weeks at standard temperature and pressure. We have also found that the kinetics of recrystallization can be accelerated through exposure to a plasticizing vapor, such as heptane [31]. Upon vapor exposure, the shape of the DSP particles changes from a rounded, amorphous-looking geometry to a more crystal-like structure as shown in Fig.…”

“…1 and has been described in detail in previous publications [27,28,31]. A unique feature of this system is a floating piston incorporated into the extraction vessel and is used to perform RESS from a fixed concentration solution in a batch mode.…”

“…We have found that the small DSP monomer precipitates (≤500 nm) prepared via RESS exhibit mechanical stability during polymerization possibly to the very high surface to volume ratio of the particles. In addition, due to the rapid quenching inherent to the RESS process, the DSP precipitates are formed in a largely amorphous, metastable state [31]. Fig.…”

“…Fig. 6c shows an AFM image of 100-300 nm diameter DSP particles precipitated from a 0.15 wt% F22 solution at a pre-expansion pressure and temperature of 345 bar and 120 • C, respectively [31]. The DSP monomer precipitates were polymerized by UV exposure (10-15 min) in the solid state for stabilization before imaging.…”