Vapor Deposition of Functional Porous Polymer Membranes

Abstract

The fabrication of porous polymer membranes is currently dominated by solution-phase processing techniques. We recently developed a versatile solventless method to deposit porous polymer membranes. In this paper, we will review the mechanism that governs the fabrication process, the advantages and capabilities of the technique, and potential applications for these membranes. In the fabrication process, low substrate temperatures are used to transition the monomer vapor into solid microstructures which are then polymerized using a thermally cleavable vapor-phase initiator. This paper covers the effect of processing parameters such as time and temperature on the molecular weight distribution of the polymer and the porosity of the membranes. We will discuss several methods for patterning and cross-linking the membranes, and we will demonstrate that asymmetric membranes with varying chemical functionalities and thicknesses can be fabricated. Finally, we will review potential applications for these membranes.

Scratch-Resistant Porous Polymer Coatings with Enhanced Adhesion to Planar and Curved Substrates

“…Porous polymer coatings have applications in drug delivery devices, , biosensors, , and separations. , Porous polymers are commonly synthesized using liquid-phase processing techniques such as phase inversion, , cryopolymerization, , and solvent casting and particulate leaching. , The presence of solvents in these techniques can cause swelling and degradation of substrates and also limit the conformality of the coatings onto curved surfaces . We recently developed a solvent-free and substrate-independent method to grow porous polymers from vapor-phase precursors. − The all dry and bottom-up nature of our fabrication process eliminates solubility requirements and surface tension issues such as dewetting and clogging and provides a high degree of control over chemical composition and thickness.…”

Synthesis of pH-Responsive Polymer Sponge Coatings and Freestanding Films via Vapor-Phase Deposition

“…The annealing process helps control dissolution of the sponge coating through partial conversion of MAA to MAN but does not prevent dissolution since the sample is not covalently crosslinked. The P­(MAA- co -MAN) coating can be permanently crosslinked by exposure to strongly nucleophilic 1,3-diaminopropane vapors. ,, …”

“…The P(MAA-co-MAN) coating can be permanently crosslinked by exposure to strongly nucleophilic 1,3-diaminopropane vapors. 19,33,47 For applications such as oil/water separation 48 and wound dressings, 33,49 it is important for the porous coating to have good adhesion to the underlying substrate. We have previously shown that we can increase the adhesion of the pillared coatings shown in Figure 1a to underlying substrates through the incorporation of the epoxide-containing glycidyl methacrylate (GMA) monomer into the fabrication process.…”

“…Vapor-phase techniques such as initiated chemical vapor deposition (iCVD) offer a more sustainable route to synthesizing porous polymer materials since solvents and additives are not required . In this paper, we show that we can adjust the iCVD process to create three-dimensional polymer sponge coatings and self-standing films with interconnected pores.…”

Self‐Wrinkling Vapor‐Deposited Polymer Films with Tunable Patterns

“…Gas-phase monomer and peroxide initiator molecules flow into a vacuum chamber with fixed pressure where a hot wire filament activates the initiator and monomer adsorbs to the surfaces of samples placed on a relatively cool stage. The iCVD technique characteristically applies conformal polymer coatings on substrates of arbitrary shape and has been extensively used for coating non-planar materials including nanopores, [53][54][55] membranes, [56][57][58] scaffolds, [59][60][61] and fabrics. [62][63][64] The technique is particularly useful for preparing polymer coatings that are difficult to process in solution due to solubility or surface energy constraints, such as fluoropolymers.…”