Northeastern University

Thomai Panagiotou

Yiannis A Levendis

Richard Flagan

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.

Process for producing polymer coatings with various porosities and

A process for producing spherical polymer particles which may be either monodisperse of a predetermined and controlled size, or polydisperse, using a liquid atomization technique. The process includes an aerosol generator to create a stream or multiple streams of liquid droplets sprayed into a thermal reactor. The aerosol generator sprays the feed solution which comprises liquid organic monomers or semi-polymerized monomers, a polymerization catalyst and optionally, a solvent, into the thermal reactor environment. The solvent evaporates allowing polymerization reactions to commence. Polymerization may proceed by a variety of methods. Polymerization is completed during the flight-time of the droplets and the solid polymer particles are collected at the bottom of the reactor. The size of the particles in every batch may be predetermined and controlled by fine tuning the aerosol generator's configuration or operational parameters to adjust the size of the droplets of the feed solution being sprayed into the reactor. In one variation, the feed solution to the aerosol generator may be a polymer dissolved in an appropriate solvent. The aerosol generator then sprays the polymer solution in the thermal reactor to generate particles by evaporating the solvent.

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Chelsea, MA, United States of America

Thomai Panagiotou