A facile and innovative method for the fabrication of highly fluorescent micro-patterns is presented, which operates on the principle of phototriggered phase transition and physical mass migration in the crystalline film of a cyanostilbene-type aggregation-induced enhanced emission (AIEE) molecule ((Z)-2,3-bis(3,4,5-tris(dodecyloxy)phenyl) acrylonitrile) with liquid-crystalline (LC) mesomorphic behavior.

A dendritic molecule of poly(propylene imine) whose periphery is modified with photoresponsive mesogenic azobenzene units was synthesized. This compound exhibited highly ordered smectic B or smectic A layer structure orienting parallel to the substrate in the film state. When this film of 90 nm thickness on a hydrophilic substrate was exposed to UV (365 nm) light, the initial flat film morphology started to form holes followed by a drastic transformation to form separated dome structure of micrometer levels. Upon continuous UV light irradiation, the domain height increased and reached to a level of ca. 8-fold higher than that of the initial thickness, which can be correlated with the disordering of layer structures as revealed by grazing angle incidence X-ray diffraction measurements. This phototriggered dewetting behavior depended on the film thickness. The thinner film resulted in local migrations to form the smaller and more homogeneous domes. The dewetting was observed below a threshold thickness of 100 nm. By UV light irradiation through a photomask, phototriggered migration at micrometer distances also occurred. By the combination of phototriggered migration and concerted dewetting, characteristic hierarchical morphologies were formed, depending on the initial film thickness. This work proposes a new possibility to control and design the dewetting processes of thin films using the dendritic material.

Vertically oriented cylinders via the directional coalescence of the spheres embedded in the blend thin films from polystyrene-b-poly(4-hydroxyl styrene) (PS-b-PHS) and PEG induced by solvent annealing were achieved. Removal of PEG water led to the formation of nanochannels throughout the films. The diameter of these channels could be as small as 9 nm which might enhance the applicability of the nano-porous films as size-selective membranes and controllable drug delivery systems for the objects less than 10 nm.