PeakForce QNM AFM study of chitin-silica hybrid films

Chitin-silica hybrid thin films, prepared through the colloidal self-assembly of chitin nanorods and siloxane oligomers, have been studied for the first time by PeakForce QNM AFM mode to explore their structure and mechanical behaviour. The change in structure and mechanical properties of chitin-silica hybrids is mainly driven by the relative quantities in chitin nanorods and silica, expressed as the chitin volume fraction ϕchi. The coating of the chitin polysaccharide by silica leads to an increase of the nanorods diameter and films surface roughness at small ϕchi values. The DMT (Derjaguin-Muller-Toporov) modulus increased both at small ϕchi due to a large amount of silica and at very high ϕchi → 1 due to an incomplete tip penetration between nanorods. The local parallel orientation of nanorods observed at different ϕchi values resulted in a modulus increase due to an enhancement of the cohesion between nanorods.