Patent ID: 8127937

Claim:
A process for separating at least one gas or liquid from a mixture of gases or liquids using a cross-linked polybenzoxazole or polybenzothiazole polymer membrane, said process comprising: a) providing a cross-linked polybenzoxazole or polybenzothiazole polymer membrane prepared from cross-linkable polyimide polymers comprising cross-linkable functional groups found in a backbone of said cross-linkable polyimide polymers and pendent —OH or —SH groups ortho to a heterocyclic imide nitrogen wherein said cross-linkable polyimide polymers are first converted to a polybenzoxazole or a polybenzothiazole polymer by thermal conversion and then said polybenzoxazole or said polybenzothiazole polymer is subjected to a crosslinking treatment wherein said cross-linked polybenzoxazole or polybenzothiazole polymer membrane is permeable to at least one gas or liquid; b) contacting a mixture of gases or liquids on one side of the cross-linked polybenzoxazole or polybenzothiazole polymer membrane to cause at least one gas or liquid to permeate the cross-linked polybenzoxazole or polybenzothiazole polymer membrane; and c) removing from an opposite side of the membrane a permeate gas or liquid composition that is a portion of said at least one gas or liquid that permeated the membrane wherein said crosslinkable polyimide polymers comprise a plurality of first repeating units of a formula (II), wherein formula (II) is: wherein X1 of formula (II) is selected from the group consisting of and mixtures thereof, X2 of formula (II) is either the same as X1 or is selected from the group consisting of and mixtures thereof, —Y— of formula (II) is selected from the group consisting of and mixtures thereof, —Z—, —Z′—, and —Z″— are independently —O— or —S—, and —R— is selected from the group consisting of and mixtures thereof.