Fabrication and Study of Switchable Polymer Layers with Hydrophobic/Hydrophilic Behavior

The framework of this thesis aims to fabricate materials, which change surface characteristics in response to environmental conditions. This response may be employed to improve material characteristics as adhesion, wettability, interaction with cells etc. The mixed brushes introduce adaptive and switching behavior in different surrounding media. Two main approaches were employed to fabricate mixed polymer brushes: "grafting to" and "grafting from". Mixed PS/PVP polymer brushes were synthesized via step-by-step grafting of these two polymers from polyamide (PA) surfaces. NH3 plasma was used for the introduction of amino and OH functionalities on PA surfaces with following attachment of azo initiator of radical polymerizaton. The mixed brushes prepared on the surface of PA textiles combine both the switching effect and effect of composite surface (i.e. micrometer scale roughness) which substantially amplifies the switching range. Mixed polymer brushes prepared from P(S-b-2VP-b-EO) and P(S-b-4VP) block copolymers were grafted to both the flat surface of Si wafers and to the surface of silica nanoparticles via quaternization reaction of the pyridine nitrogen. This one step grafting technique has a substantial advantage over the multistep grafting of mixed polymer brushes. We have demonstrated that combination of the two level hierarchical organization of polymer films at macroscopic and nanoscopic levels resulted in the formation of self adaptive surfaces switchable in controlled environment from ultra-hydrophobic to hydrophilic energetic states. The PFS/PVP mixed brush was grafted onto the pre-treated PTFE surface (plasma etching) with the needle like topography. The size of vertical needles was at micron scale. If the brush is switched to the hydrophobic state the layer has shown a unique ultra-hydrophobic behavior (complete non-wetting) with the contact angle approaching value of 160o. If the mixed brush was switched into the hydrophilic state the surface became completely wetted due to the capillary forces in the pores formed by the needle like structure. Thus, the surface can be either highly wettable or completely non-wettable with the self cleaning properties