Photopatterning on polymer films has attracted extensive attention due to its widespread applications. Nevertheless, it is still challenging to rewrite these patterns. Herein, we demonstrate a viable approach toward the rewritable polymer films based on topopolymerization of the diacetylene monomer (e.g., 10, 12-pentacosadiynoic acid, PCDA) in poly(propylene carbonate) (i.e., PPC). Rewritability of at least 17 times through the reversible colorimetric change of polydiacetylene (PDA) is achieved, and the written information can be maintained for 9 months under ambient conditions. Moreover, it is found that the hydrogen bonding interaction between PCDA and PPC plays a key role in improving the rewriting performance according to variable temperature Fourier transform infrared spectroscopy and molecular dynamics simulations. Well-defined assembly of PCDA along the PPC main chain is enabled, which leads to improved topo-polymerization of PCDA. The proposed paradigm here paves the way to design rewritable polymer films with customized patterning.

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 (SDr) 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 SDr 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.

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