Abstract: A junction selective contaminant exclusion tool includes a tubular positionable within the junction and having an opening through a wall thereof, a material disposed on an outside surface of the tubular, the material being capable of increasing a radial dimension between a surface of the material in contact with the tubular and an opposite surface of the material upon exposure to a selected species. A method for excluding selected contaminants from a wellbore junction is also disclosed. The method includes: disposing a junction at a wellbore casing window; disposing a tubular member having at least one opening through a wall thereof at the junction, the tubular member including an exclusion material thereon capable of existing in a first configuration and a second configuration, the second configuration obtainable upon exposure to a selected species; and exposing the material to the selected species.