Alteration of the mechanical properties of azopolymer film in the process of surface relief grating formation

摘要

Alterations of local hardness in azopolymer films have been investigated using atomic force microscope after light-induced surface relief gratings inscribed at temperatures between 25 ℃ and the glass transition. Compared to nonpatterned regions of same material, local hardness is increased at positions of crests but reduced in troughs. Surface relief gratings on films at room temperature show relative hardness variation up to 50% and decreases linearly with grating height and temperature. The findings can be explained by increased/decreased density of parallel-aligned polymer chains in crests/troughs as result of cooperative motion due to trans-cis-trans isomerisation during grating formation in competition with thermal disorder.