Polyvalent surface modification of hydrocarbon polymers via covalent layer-by-layer self-assembly
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Layer-by-layer (LbL) assembly based on ionic interactions has proven to be a versatile route for surface modification and construction of ultrathin nanocomposites. Covalent LbL assembly based on facile ‘click’ covalent bond formation is an effective alternative, especially for the applications where a more robust ultrathin films or nanocomposites is desired. The subject of this dissertation focuses on the design of three different 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 and Gantrez 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 surface provided excellent coverage and promoted stable LbL film growth and excellent adhesion. This carbon black (CB) coated powder was compression molded into films, and their conductivity was measured, which revealed a percolation threshold below 0.01 wt % CB for the PEI-grafted system. Electrical conductivity of 0.2 S/cm was achieved with only 6 wt % CB, which is exceptional for a CB-filled PE film. Direct amination of MWNTs with PEI is a convenient and simple method leading to highly functionalized product that contains 6-8 % by weight PEI. Superhydrophobic PE films can be formed either from ionic LbL self-assembly of MWNT-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 the ionically assembled nanocomposite graft is labile under acid, the covalently assembled graft is more chemically robust. Responsive surfaces with significant, reversible, reproducible wettability changes can be prepared by covalent LbL grafting using PNIPAM-c-PNASI and aminated silica nanoparticles. A 65º ΔΘ value was observed with water vs. 1.4 M Na2SO4. The prepared film shows a high surface roughness of ~300 nm, which contributes to the large solute responsive ΔΘ values. The surfaces are reconfigurable in different solute conditions and that the changes in water contact angle are likely due to combination of change in surface roughness along with swell and intercalation of the solute ions into the PNIPAM surface.
Liao, Kang-Shyang (2008). Polyvalent surface modification of hydrocarbon polymers via covalent layer-by-layer self-assembly. Doctoral dissertation, Texas A&M University. Available electronically from