Gas plasma polymerized permselective membrane

A method of making a permselective composite membrane comprising:

• providing a gaseous blend comprising a disiloxane and added oxygen within a vacuum chamber, wherein the disiloxane has a formula R.sub.1 R.sub.2 R.sub.3 Si--O--SiR.sub.1 R.sub.2 R.sub.3 where R.sub.1, R.sub.2, and R.sub.3 are individually either methyl or ethyl groups, exciting the gaseous blend to a gas plasma by means of a glow discharge, bringing a porous substrate into contact with the gas plasma, and depositing upon the porous substrate a plasma polymerizate comprising a polysiloxane, wherein the plasma polymerizate is deposited at a rate that is increased due to presence of the added oxygen in the gaseous blend, thereby generating a permselective composite membrane.

A membrane comprising:

• a porous substrate having a contiguous coating of a plasma polymerizate comprising a polysiloxane deposited thereon from a gas plasma comprising a fully alkylated disiloxane and added oxygen, wherein the plasma polymerizate has been deposited at a rate that is increased due to presence of the added oxygen in the gaseous blend, thereby generating a permselective composite membrane.

A module for separating gaseous mixtures comprising:

• a shell means having spaced end portions and defining an elongated chamber therebetween,
• a plurality of permselective composite hollow fiber membranes having an oxygen permeability of at least about 1.5.times.10.sup.-4 cm.sup.3 /cm.sup.2 -sec-cmHg and an oxygen/nitrogen selectivity ratio of greater than 2.3, the membranes comprising a porous hollow fiber substrate having a plasma polymerizate comprising a polysiloxane deposited on a surface thereof, the plasma polymerizate being deposited from a gas plasma formed by glow discharge through a gaseous blend comprising a fully alkylated disiloxane and added oxygen, the plasma polymerizate having been deposited at a rate that is increased due to presence of the added oxygen in the gaseous blend, wherein the membranes extend in a substantially parallel relationship within the elongated chamber, the membranes defining an intracapillary space within the hollow fibers and an extracapillary space outside the hollow fibers, fluid communication between the intracapillary and extracapillary spaces being only by means of permeation through the polysiloxane polymerizate coating,
• means for communicating a gaseous fluid with the extracapillary space, and means for removing a gaseous permeate from the intracapillary space.

An article comprising a substrate having at least one surface, the surface being coated with a plasma polymerizate comprising a polysiloxane, the plasma polymerizate being deposited on the surface from a gas plasma formed from a gaseous blend comprising a vapor of a fully alkylated disiloxane and oxygen, the disiloxane vapor being present in the gaseous blend at a partial pressure of at least about 0.01 Torr to at least about 1.5 Torr, the oxygen being present at a partial pressure ratio of at least about 0.1 to at least about 2.0 relative to the disiloxane vapor, the plasma polymerizate being deposited at an increased rate due to presence of the oxygen in the gaseous blend.