Polyvalent surface modification of hydrocarbon polymers via covalent layer-by-layer self-assembly

摘要

Layer-by-layer (LbL) assembly based on ionic interactions has proven to be aversatile route for surface modification and construction of ultrathin nanocomposites.Covalent LbL assembly based on facile ?click? covalent bond formation is an effectivealternative, especially for the applications where a more robust ultrathin films ornanocomposites is desired. The subject of this dissertation focuses on the design of threedifferent covalent LbL assemblies and their applications on conductive thin films,superhydrophobic surfaces, and solute responsive surfaces, respectively.Surface modification of PE substrates using covalent LbL assembly with PEI andGantrez is a successful route to prepare a surface graft. The procedure is relative easy,fast and reproducible. Grafting multiple layers of PEI/Gantrez to the PE powder surfaceprovided excellent coverage and promoted stable LbL film growth and excellentadhesion. This carbon black (CB) coated powder was compression molded into films,and their conductivity was measured, which revealed a percolation threshold below 0.01wt % CB for the PEI-grafted system. Electrical conductivity of 0.2 S/cm was achievedwith only 6 wt % CB, which is exceptional for a CB-filled PE film. Direct amination of MWNTs with PEI is a convenient and simple methodleading to highly functionalized product that contains 6-8 % by weight PEI.Superhydrophobic PE films can be formed either from ionic LbL self-assembly ofMWNT-NH-PEIs and poly(acrylic acid) or from covalent LbL self-assembly of MWNTNH-PEIs and Gantrez when the final graft is acrylated with octadecanoic acid. While theionically assembled nanocomposite graft is labile under acid, the covalently assembledgraft is more chemically robust.Responsive surfaces with significant, reversible, reproducible wettability changescan be prepared by covalent LbL grafting using PNIPAM-c-PNASI and aminated silicananoparticles. A 65? ?? value was observed with water vs. 1.4 M Na2SO4. The preparedfilm shows a high surface roughness of ~300 nm, which contributes to the large soluteresponsive ?? values. The surfaces are reconfigurable in different solute conditions andthat the changes in water contact angle are likely due to combination of change insurface roughness along with swell and intercalation of the solute ions into the PNIPAMsurface.