Preparation And Characterization Of Several Poly(Ionic Liquid) Films With Tunable Wettabitily

Wettability is one of the important properties of the solid surface which isgoverned by surface free energy and surface roughness．In the past few years,superhydrophobic surfaces with water contact angles larger than 150°have receiveda lot of research attention．At present there are many mature methods to be used tomake superhydrophobic surfaces．But the tunable wettability surfaces switchingbetween superhydrophilicity and superhydrophobic reversibly have attracted moreand more interest due to their important applications, such as self-cleaning materials,microfluidic devices and variable-focus lens．As a result, it still remains a greatchallenge to construct the materials with high stability and excellent reversible tunablewettability using with simple and convenient techniques．Surface initiated polymerization is an effective method to modifying surfaceproperties of the substrate, which can be used to tether poly(ionic liquid)unit onto asolid substrate and switch the surface wettability through choosing propercounteranions．In this thesis, different poly(ionic liquid)films have successfully grafted ontomonocrystalline silicon substrates through surface radical chain-transfer reaction．Thetunable wettability of the films can be achieved by counteranions exchange．1-allyl-3-methylimidazolium chloride ([AMIM]Cl) , 1-allyl-3-butylimidazoliumchloride ([ABIM]Cl) and allyltriphenyphosphonium chloride(ATPP-Cl) wererespectively employed as monomer to carry out SIP reaction．First, thiol-terminatedself-assembled monolayer was fabricated on hydroxylated monocrystalline siliconsubstrates by molecular self-assembly technique of 3-mercaptopropyltrimethoxysilane．Then, [AMIM]Cl, [ABIM]Cl and ATPP-Cl was initiatedrespectively to polymerize on silicon surfaces in-situ by usingazobisisobutyronitrile(AIBN)as initiator, DMF as solvent through surface radicalchain-transfer reaction．As a result, three hydrophilic surfaces respectively modifiedby P[AMIM]Cl, P[ABIM]Cl and PATPP-Cl were obtained．The chemical states ofsome typical elements in the polymer films were analyzed using X-ray photoelectronspectroscopy (XPS), the morphology of the thin films was observed using an atomic force microscope(AFM)and the thicknesses of the films were measured with aspectroscopic ellipsometer．The static water contact angles were determined usingstatic water contact angle goniometer．The results showed that the poly(ionicliquid)films were successfully grafted onto the silicon substrates and the morphologyof the thin films was rather uniform．Moreover, the tunable wettability of the filmscan be easily achieved by exchanging their counteranions continuously．...