Poly(L-lactide) Substrates with Tailored Surface Chemistry by Plasma Copolymerisation of Acrylic Monomers

The wettability of PLLA substrates was modified by plasma copolymerising on its surface thin films based on EA and HEA. The composition of the reactive gas inside the plasma chamber was that of the corresponding liquid mixture of the comonomers. The surface of the substrates was investigated by AFM, which showed that the plasma film was approximate to 100 nm thick. The WCA decreases monotonically with decreasing HEA content in the mixture. The fraction of hydroxyl groups has been calculated from XPS. The local mechanical properties of the plasma-polymerised surfaces were estimated by nanoindentation experiments performed using the AFM tip, which turns out to be a method sensitive to the composition of the copolymerised plasma film on the PLLA surface.