Multi-scale ordered patterns in photosensitive ternary polymer mixtures

Abstract

Multi-scale ordered patterns of multi-component polymer mixtures can reveal many peculiar chemical and physical properties, which makes these systems have very important potential applications in materials engineering. Via computer simulation, we create interesting ordered multi-scale structures in photosensitive and immiscible polymer mixtures. The system that we employed comprises a ternary, molten A/B/C polymer blends and the three components are mutually immiscible. Polymer C is non-optically active, while polymers A and B can exhibit reversible chemical reaction A ⇆ B induced by light. Firstly, we investigate the phase behavior of the ternary blend guided by cross-stripy mask and light, and find that a chessboard-like ordered pattern forms in the mixture before removing the mask. In the illuminated regions, the A and C components gather into ellipsoidal core-shell structures in the uncrossed illuminated area, while the A and B components gather into star structures in the crossed stripes regions. When we remove the mask, the entire system becomes illuminated, and the reaction A ⇆ B occurs throughout the film: the ellipsoidal core-shell structures of A and C components turn to spherical structures, and the star structures of A and B components turn into concentric square ring structures. Then we show the influences of the number of cross stripes and the initial composition on the formation of structure. The average spatial volume fraction of C component first increases and then decreases with the stripy number increasing and the C component net lattices play an important role in the stability of ordered structures. Secondly, when the blend is covered by the annular mask, the C component gathers to the illuminated regions and the A and B components are in radial arrangement. As a result, the mixture forms an interesting dartboard-like pattern. However, when the mask is removed, the photochemical reactions occur in the A and B components of the whole region, the increasing of free energy induces the dartboard-like pattern to be broken and to change into dots-ring structure and then it forms a perfect concentric ring pattern and the target-like pattern. And also, we show the effects of initial composition ratio of C component, the distance between two adjacent rings D, the ring width d, and the illumination intensity on the evolution of ordered structure. The larger the initial composition ratio of C component, the more easily the ordered target-like pattern forms; the larger the distance D and the smaller the width d, the better the pinning effect of C component is. The illumination intensity has little influence on the ordered morphology of the ternary system. We provide a simple approach to creating multi-scale patterned films with long-range order, which could guide us in fabricating nanoscale devices.