Process for producing polymer coatings with various porosities and

Abstract

A process for forming polymer coatings on the surfaces of objects, e.g., medical stents, is disclosed. The coatings formed by the process of the invention comprise small spherical, spheroidal or irregular shape polymer particles, which may be adhered together. Coatings may have high porosity and high surface area. The process includes the steps of preparing a liquid feed solution of either mixtures of liquid organic monomers and polymerization catalysts which may optionally be pre-polymerized, or polymers dissolved in solvents; conducting the liquid feed solution into an aerosol generator; generating either a controlled or uncontrolled aerosol in the form of droplets; spraying the liquid feed solution from the aerosol generator into a thermal reactor on to the surface of an object; regulating the temperature and pressure of the reactor so that a portion of the solvent in the feed solution evaporates before the droplets are deposited on the object; and maintaining the spray of the liquid feed solution in the thermal reactor for an optimum period of time to allow the coating to form on the object. Optionally, another material, such as a drug, carbon black, calcium carbonate, etc., is added to the feed solution, as well. The experimental conditions are adjusted so that some of the solvent evaporates before the droplets hit the surface of the object. This can be done if the temperature of the surroundings is sufficiently high, the ambient pressure is significantly low, the residence time of the droplets is sufficiently long, or a combination of the above.