Thermocapillary Marangoni Flows in Azopolymers.

Area of Science:

• Polymer Science
• Optics
• Surface Science

Background:

• Light-induced trans-cis-trans photoisomerizations of azobenzene derivatives cause polymer mass movement and surface relief generation.
• Optofluidization and photo-induced molecular orientation occur with polarized light, leading to optical anisotropy.
• High laser intensities can lead to significant surface reliefs via optofluidization.

Purpose of the Study:

• To investigate the competitive interplay between optofluidization and the thermocapillary Marangoni effect in azopolymer mass motion.
• To experimentally demonstrate the simultaneous occurrence of the Marangoni effect and optofluidization.
• To analyze the impact of the Marangoni effect on molecular orientation and photo-induced birefringence.

Main Methods:

• Experimental observation of polymer surface topography using atomic force microscopy.
• Investigation of light-induced mass movement and surface relief generation in azobenzene-containing polymers.
• Modeling to support experimental observations of polymer behavior under illumination.

Main Results:

• The thermocapillary Marangoni effect was experimentally proven to occur simultaneously with optofluidization.
• The Marangoni effect was shown to disrupt the directional orientation of azopolymer molecules.
• Photo-induced birefringence was canceled due to the influence of the Marangoni effect.

Conclusions:

• The Marangoni effect is a significant factor in azopolymer mass motion, competing with optofluidization.
• Simultaneous optofluidization and Marangoni effect lead to complex surface topography and loss of optical anisotropy.
• Understanding this competition is crucial for controlling surface relief generation and optical properties in azopolymer systems.