Method for depositing a barrier coating on a polymeric substrate and composition comprising said barrier coating

A method for depositing a barrier coating on a polymeric substrate, the method comprising the steps of:

• treating a surface portion of the polymeric substrate to remove any contaminants, said treating step comprising:
• cleaning ultrasonically the substrate in a solution of detergent,
• rinsing the substrate in deionized water,
• rinsing the substrate in methanol,
• drying the substrate in an oven at a temperature of about 80° C. for at least one hour, and
• blowing off the substrate with deionized nitrogen gas;
• depositing at least one layer of a parylene polymer on the surface of the polymeric substrate via chemical vapor deposition;
• and
• annealing by heat each deposited layer of the parylene polymer in the presence of a vacuum at an annealing temperature for a time sufficient to increase the degree of parylene crystallization.

A method for depositing a barrier coating on a clean elastomeric surface, the method comprising the steps of:

• exposing the surface to parylene N in vapor phase to form a first layer of parylene N polymer;
• shifting the exposure of said parylene N to parylene C in vapor phase upon reaching a desired thickness of the first layer to form a graded layer comprising a transitional mixture or parylene N and parylene C;
• and
• exposing the elastomeric surface to parylene C in vapor form in the absence of parylene N to form a third layer of parylene C polymer on said graded interlayer.