The morphology and wetting stability of nanofilms formed by AyByCz miktoarm star terpolymers were explored by many-body dissipative particle dynamics. The length ratio of C- to A-arm (w=z/y) ranges from 0.25 to 5. On nonselective substrates, the nanofilm displays morphology as the lamella at w<0.5, various Archimedean tilings at 0.5≦w<3, and the alternating lamella at w=3. (Figure 1a) The nanofilm becomes unstable at w=5. While our findings of Archimedean tiling patterns [6.6.6], [8.8.4], and [12.6.4] are consistent with thin film experiments, [8.6.4;8.6.6] and [10.6.4;8.6.4] have not been reported. The wetting stability was determined by the final fates of thin films subject to disturbances, including (i) nucleation and growth, (ii) self-healing, and (iii) stable hole. The stability follows descending order: [6.6.6] > [8.6.4;8.6.6] > [10.6.4;8.6.4] > [8.8.4] > [12.6.4] > alternating-lamella > lamella > alternating-cylinder. (Figure 1b) On selective substrates with weaker or stronger attraction with C-arms, the defects formed by C-arms prevail for the former but the lamella morphology dominates for the latter. （諶玉真教授提供 yjsheng@ntu.edu.tw）
Figure 1. (a) Determination of the wetting stability by reducing polymer-substrate attraction (αPS). The film morphology is either unchanged (metastable) or ruptured (unstable). (b) Determination of the wetting stability by changing the initial film thickness h0. All these snapshots are taken from top views.