Wetting transitions of polymers via thermal and plasma enhanced atomic layer depositions

Polypropylene (PP) and a blend of poly(ethylene terephthalate)/cotton (PET/cotton) nonwoven fiber felts were modified using aluminum and zinc oxides via thermal and plasma enhanced atomic layer deposition (ALD and PEALD). Deposition of aluminum or zinc oxide on PP induced a wetting transition from the hydrophobic behavior characteristic of the untreated PP to a hydrophilic behavior for ALD coated PP. PEALD needed a fewer number of cycles to induce hydrophilic effect, compared to thermal ALD. This correlated with the observation of an initial nucleation delay for thermal ALD on PP, while PEALD resulted in deposition of oxide material from the initial cycles. The hydrophilic effect could be achieved for a wider range of deposition temperatures for PEALD as compared to thermal ALD. PEALD of aluminum and zinc oxides did not alter the surface properties of the PET/cotton felts, as they stayed hydrophilic even after 400 cycles of deposition, while thermal ALD of zinc oxide transformed hydrophilic PET/cotton felts to hydrophobic.