Athermal photofluidization

What is it about?

The paper presents for the first time a direct (microscopic) visualization of a "melting" process, generated by the light and not by the heat. The "melting" of the azo-polysiloxane sample is the result of the continuous trans-cis-trans isomerization process of the azo-groups (connected in the side-chain) as a result of the interaction with light. The isomerization process induces a "conformational instability" of the polysiloxanic main-chain, similar to the thermal effect.

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Why is it important?

The paper propose a new mechanism of surface relief grating (SRG) formation, involving at least three processes: (1) the polymer photo-fluidization in the illuminated regions, (2) the mass displacement from illuminated to dark regions and (3) the inverse mass displacement from dark to illuminated regions. These processes take place simultaneously, one or the other being dominant, depending on the polymer chemical structure and experimental conditions.