Tuning wettability of hydrophobic polymer surfaces through self assembly of hydrophobins and perfluoropolyethers

Wettability has important consequences on tribological features, chemical attack resistance and permeability of a surface. For this reasons, tailoring wettability is important into the industrial panorama. Perfluoropolyethers (PFPEs) are molecules designed to deposit themselves on surfaces and thus transfer them properties of fluorinated materials (low wettability, high chemical inertness, low friction coefficient, etc …). Fluorolink® F10 (F10) is a PFPE with anchoring phosphate groups. It can be used to perform amphiphobic treatment on many hydrophilic surfaces. However it doesn't adhere efficiently to apolar substrates, making difficult the application on hydrophobic polymers. This thesis work has as final target the evaluation of the ability of hydrophobins to be used as a primer layer and thus to allow the adhesion of F10 to hydrophobic polymeric surfaces. Hydrophobins are amphiphilic protein able to form a film on a substrate and invert its wettability. In such way a coulombic attraction is possible between the deposited proteins and F10. In experimental part F10 is deposited on hydrophobic surfaces with and without mediation of HFBII (the tested hydrophobin). QCM-D measures have been performed at pH: 3, 4, 5, 6, 8: polystyrene and octadecylmercaptane SAMs coated QCM chips were used. The produced samples were analysed with dodecane contact angle and AFM. Results show that F10 is not able to adhere directly to tested surfaces; instead when deposited at pH<5.8 (pI HFBII) on a primer HFBII film, F10 raises the oil contact angle to ~60°. The PFPEs deposits increase amphiphobicity, although AFM images showed that, at microscopic level, they don't homogeneously cover the surface. In the second part, parallel experiments of immersion deposition on polystyrene samples have been performed and analysed through contact angle, optical microscopy, FT-IR, SEM and AFM with results comparable to the QCM-D ones. The surfaces treated show a highly heterogeneous distribution of deposits. However it is demonstrated that the wettability modification depends only on the nanometric deposits which F10 forms only over the HFBII film.