Atomised Spray Plasma Deposition of Functional Polymer Coatings

Abstract

Atomised spray plasma deposition (ASPD) is a technique used to functionalise
surfaces. The atomisation of precursor into electrical discharges allows the
deposition of: (i) non-polymerisable precursors, which cannot be deposited
through conventional surface functionalisation methods; (ii) viscous or lowvapour-pressure precursors, which cannot be deposited in conventional gasphase plasma polymerisation; (iii) precursor–nanoparticle slurry. In this thesis,
atomised spray plasma deposition was employed to fabricate functional
polymer coatings for diverse applications such as liquid repellent, wet
electrical, and antibacterial coatings.

Liquid-repellent surfaces were fabricated by the deposition of a mixture
of nanoparticles and a perfluorinated precursor forming a highly crosslinked
polymer matrix containing the nanoparticles. The wettability of the ASPD
nanocomposite coatings resulted in water contact angle values of ~170°; the
nanoparticles, acting as nanofillers, enhanced the mechanical properties of
the ASPD polymer coatings.

Fluorine-free and low-vapour-pressure precursor was used to fabricate
hydrophobic ASPD polymer coatings and the effect of the in situ plasma posttreatment of ASPD poly (isodecyl acrylate) coatings was tested. The effect of
the plasma post-treatment enhanced the crosslinking degree, mechanical and
adhesion properties as well as the enhancement of the wet electrical barrier
of the ASPD poly (isodecyl acrylate) coatings preventing the electrical
breakdown of microcircuit boards in contact with water for an applied electric
field of 10 V mm−1. Further enhanced liquid repellency, mechanical properties,
and wet electrical barrier to at higher applied electric field (75 V mm−1) were
found for plasma post-treated ASPD 20% w/v (1H,1H,2H,2H-perfluorododecyl
acrylate–perfluorotributylamine) coatings.

Finally, bis-dodecylamine copper dichloride (CuDDA) metallosurfactant
was employed to fabricate antibacterial-agent-release 2% w/v ASPD
(CuDDA–isodecyl acrylate) coatings. It is likely that the metallosurfactant
remained trapped within the plasma polymer coating through electrostatic
interactions because there was a reduction of the antibacterial activity of the
antibacterial polymer coating as it leached out. These antibacterial polymer coating displayed highly antibacterial activity efficiency against Gram negative
E. coli and Gram-positive S. aureus bacteria. The maximum antibacterial
efficiency (>99.999%) was found at 10 min of interaction time tested on both
bacteria individually on the antibacterial ASPD polymer coating, which is
attributed to the synergetic effect of the long hydrophobic alkyl chain and the
complexation of the surfactant with Cu2+ ions.