An ionic liquid (IL) was introduced into a vapor-phase free radical polymerization process for the first time. The deposition of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) was studied in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) droplets. The polymerization occurred either at the vapor−IL interface or within the IL depending on reaction conditions such as the duration of deposition, the stage temperature, and the monomer solubility. A variety of polymeric architectures such as polymer skins that completely encapsulated the droplet, free-standing polymer, and polymer films that float freely on the surface of the IL were formed. The results from this study will facilitate the design of new polymer−IL composite materials for use in fuel cell and battery applications.

We studied the vapor deposition of polymers onto the surfaces of silicone oil and imidazolium-based ionic liquids (ILs). We found that the deposition of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(N-isopropylacrylamide) (PNIPAAm) resulted in polymer particles on silicone oil whereas continuous polymer skins formed on 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]), and 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF 4 ]). The silicone oil and ILs were patterned onto a common substrate by exploiting their different wetting properties. Ultrathin free-standing PHEMA and PNIPAAm films of different shapes were produced by confining the shape of the IL within a wax barrier, surrounding it with silicone oil, and then depositing the polymer. The silicone oil prevented the polymer film from connecting to the underlying substrate and maintained the shape of the polymer film during deposition. Our process allows for multidimensional control over the resulting free-standing film: the area of the shape can be controlled by patterning the IL, and the thickness of the film can be controlled by adjusting the duration of polymer deposition. The films are highly pure and do not contain any residual monomer or solvent entrapment which extends their potential applications to include in vivo biomedical research. ■ INTRODUCTIONThe initiated chemical vapor deposition (iCVD) technique is a one-step, solventless free radical polymerization process that can be used to deposit a wide range of polymer films such as poly(2-hydroxyethyl methacrylate) (PHEMA), 1 poly(4-vinylpyridine) (P4VP), 2 and poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA). 3 The iCVD technique is typically used to deposit polymer coatings onto solid substrates such as silicon wafers, 4 membranes, 5 wires, 6 carbon nanotubes, 7 and fibers. 8 We recently demonstrated the ability to deposit polymer coatings onto ionic liquids (ILs). 9 ILs are salts that are liquids at ambient temperatures, and they have recently attracted significant interest as environmentally friendly alternatives to traditional volatile organic solvents because they are nonvolatile, nonflammable, and can be easily recycled. 10,11 Our previous work examined the deposition of PHEMA and PPFDA in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) droplets. We found that polymerization occurred at the vapor−IL interface and/or within the bulk IL depending on the solubility of the monomer within the IL and the reaction conditions such as the duration of deposition and stage temperature.In this paper, we use iCVD to deposit polymers onto silicone oil for the first time. We observe different polymer morphologies on the silicone oil as compared to the ILs, and we exploit this difference to fabricate ultrathin free-standing polymer films of different shapes by combining the silicone oil and ILs onto a common substrate. The generality of our fabrication method is demonstrated for multiple po...

We studied a new method for preparing polymer–ionic liquid (IL) gels via deposition of vapor phase precursors onto thin layers of IL. The solubility of 2-hydroxyethyl methacrylate in 1-ethyl-3-methylimidazolium tetrafluoroborate enabled polymerization at both the IL–vapor interface and within the IL layer. We observed a transition from a viscous liquid to a gel with increasing polymer concentration. At short deposition times, there were two distinct molecular weights reflecting polymerization at the IL–vapor interface and within the IL layer, while at longer deposition times the molecular weight distribution within the IL layer broadened. The polymer chains within the IL were orders of magnitude larger than the polymer chains at the IL–vapor interface, and increasing the reactor pressure was shown to increase the molecular weight. Our ability to form high molecular weight polymer chains allows for the formation of gels for utilization as fuel-cell membranes and thin-film transistors.

In this article, we study the growth of polymer nanoparticles that are formed on the surface of silicone oils via initiated chemical vapor deposition. The average radius of the particles can be increased by decreasing the silicone oil viscosity, increasing the deposition time, or increasing the deposition rate. The time series data indicates that there are two stages for particle growth. Particle nucleation occurs in the first stage and the particle size is dependent on the liquid viscosity and deposition rate. Particle growth occurs in the second stage, during which the particle size is dependent only on the amount of deposited polymer. This two-step process allows us to make core-shell particles by sequentially depositing different polymers. The benefits of our nanoparticle synthesis process are that solvents and surfactants are not required and the size of the nanoparticles can be controlled over a wide range of radii with a relatively narrow distribution.

In this work, we study the use of initiated chemical vapor deposition in conjunction with liquid scaffolds to deposit polymer canopies onto structured surfaces. Liquid is applied to micropillar and microstructure surfaces to act as a scaffolding template such that the deposited polymer films take the shape of the liquid surface. Two methods for directing the location of the scaffolding liquid were examined. In the first method, high surface tension liquids rest in a Cassie-Baxter state over the structured surfaces, allowing for control over the canopy location and size by varying the position and volume of the liquid. In the second method, the structured surfaces are inverted onto a thin layer of low surface tension liquid, allowing the coverage and height of the canopy to be controlled by varying the area and thickness of the liquid layer. Although the canopies demonstrated in this study were fabricated using initiated chemical vapor deposition, the generality of our scaffolding method can easily be translated to other vapor deposition processes.