Formation of Porous Polymer Coatings on Complex Substrates Using Vapor Phase Precursors

Abstract

In this work, porous poly(methacrylic acid) (PMAA) coatings are formed on complex substrates using vapor phase precursors. The porous coatings are created by partially polymerizing solid monomer deposited onto the substrate. The conformality of the porous PMAA coatings is studied on the external and internal surfaces of cylindrical substrates. Flow effects lead to thickness variations in the θ‐direction while thermal gradients and monomer depletion effects lead to thickness variations in the z‐direction. These variations can be reduced by modifying the flow rate of the monomer vapor, by reducing the radiative heat on the substrate, or by increasing the dimension size of the substrate. This work shows that vapor phase processing methods can be a viable alternative to solution phase methods and the observed trends can be utilized in a range of vapor phase technologies to optimize porous coatings for use in tissue engineering, sensors, and separations.

Chemically vapor deposited polymer nanolayers for rapid and controlled permeation of molecules and ions

“…Novel iCVD processes allowed formation of free-standing microporous poly(MAA) layers of interest for membrane separation and tissue engineering applications. 64,76,77 For paper-based microfluidics, the low surface growth temperature of iCVD allowed MAA-based membranes to be fabricated directly on paper substrates. 78 Annealing these membranes resulting in condensation of some of the -COOH groups to anhydride functionalities, producing a finer pore structure.…”

Process–Structure–Property Relationships for Porous Membranes Formed by Polymerization of Solid Monomer by a Vapor-Phase Initiator

“…Free radicals that are formed by thermally cleaving the initiator molecules react with the monomer to start polymerization. Unreacted solid monomer is then removed through sublimation, and the porous polymer membrane remains. ,, Larger pores on the order of tens to hundreds of micrometers in magnitude form due to empty spaces between the solid microstructures and smaller pores form on the order of hundreds of nanometers inside the microstructures. Using this method, we have previously shown the fabrication of porous-on-porous membranes, asymmetric membranes, and patterned porous polymer membranes …”

Vapor Phase Fabrication of Hydrophilic and Hydrophobic Asymmetric Polymer Membranes

“…Our group recently demonstrated that the iCVD process can also be used to fabricate membranes by increasing the monomer partial pressure above its saturation pressure and lowering the substrate temperature below the freezing point of the monomer. These nonconventional conditions lead to the simultaneous deposition of solid monomer and polymerization . The unreacted solid monomer is removed after the deposition which leads to the formation of membranes with dual‐scale porosity.…”

“…These nonconventional conditions lead to the simultaneous deposition of solid monomer and polymerization. [ 25,26 ] The unreacted solid monomer is removed after the deposition which leads to the formation of membranes with dual-scale porosity.…”