Gas Permeation Through Nanoporous Polycarbonate Track- Etched Membranes: Pulsed Plasma Polymerization Of Thin Coatings To Modulate Gas Permeability
Chapman, Christopher Lewis
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Polycarbonate track-etched membranes (PCTE) of 50nm and 100nm pore size, precoated with Poly Vinyl Pyrrolidone (PVP), were surface treated with either Vinyl Acetic acid (VAA) or Perfluorohexane (C6F14) using a low duty cycle pulsed plasma polymerization technique. The effects of this surface treatment on gas permeation properties of the PCTE were addressed. Plasma coating thickness was controllably varied and resulted in gradual reduction of O2 and CO2 permeability as thickness increased from 10nm to 100nm. Plasma coating material, permeant gas, membrane pore size, and crosslink density were also varied in order to gain insight into the permeation properties of the PCTE. The results show the wide range of permeability achievable via this method. O2 was more permeable than CO2 as expected. Varying the crosslink density had a noticeable effect on the gas permeability as well as the surface wettability. Also, the results from advancing/receding contact angle measurements indicate a much more hydrophobic character when the surface was coated with C6F14 compared to the uncoated and VAA coated samples. Blood oxygenation is an intended future application of this process. It was shown that the modified PCTE membranes had sufficient O2 and CO2 transfer for this purpose. This study supports the idea of utilizing the plasma polymerization process to modulate the gas permeability characteristics of the PCTE membranes and also alter the membrane surface to improve performance.