Computational Insight into Phase Separation of a Thiol-Ene Photopolymer with Liquid Crystals for Holography by Dissipative Particle Dynamics Simulation

Holographic polymer nanocomposites comprising liquid crystals (LCs) are produced through periodic photopolymerization-induced phase separation upon laser interference. A high degree of phase separation normally favors the holographic function which is, however, difficult to predict. Herein, we demonstrate the first example of providing computational insights into the phase separation by dissipative particle dynamics simulation. Phase separation to produce alternating polymer-rich and LC-rich regions occurs in the way that LC molecules transfer from bright to dark regions upon laser interference when the thiol-ene click reaction takes place in the bright regions. Results show that the relative segregation degree (SD_r) increases with LC content when it is lower than 40 wt %, which can be correlated with the transferred amount of LC molecules from bright to dark regions. The low SD_r of the system with 40 wt % LC may be ascribed to the inhibitory LC transfer by polymerization compared with the case prior to reaction. In terms of the effects of reaction probability, either too high or too low reaction probability is not favorable for phase separation due to insufficient LC transfer. Despite that no nematic LC phase is found after phase separation, this work provides initial computation insights into the mass transfer behaviors during photopolymerization-induced phase separation, which help in the development of effective strategies to improve the phase separation and performance of holographic polymer nanocomposites.