Microstructuring of polymers using a light-controlled molecular migration processes

The manipulation and precise control of molecular order is a challenging prospect in the design and realization of devices for photonic applications. A new concept for microstructuration, based on photoinduced molecular migration in polymer films containing an azobenzene dye, was recently demonstrated. Irradiation with an interference pattern of polarized laser beams leads to substantial reversible mass-transport. We now show evidence that under specific experimental conditions, the interaction between a uniform beam from an argon-ion laser and the polymer film induces hexagonal structures on the surface of the polymer. The self-patterning process was observed to depend on several parameters such as the polarization of the laser beam, the angle of incidence and the wavelength, as well as the nature of the dye. Understanding the fundamental mechanisms of this photoinduced self-patterning process should open a new route towards optical molecular control of materials microstructures.