CVD Polymers Gleason, Karen K
2015, 2015-03-05, 2015-04-01
eBook
The method of CVD (chemical vapor deposition) is a versatile technique to fabricate high-quality thin films and structured surfaces in the nanometer regime from the vapor phase. Already widely used ...for the deposition of inorganic materials in the semiconductor industry, CVD has become the method of choice in many applications to process polymers as well. This highly scalable technique allows for synthesizing high-purity, defect-free films and for systematically tuning their chemical, mechanical and physical properties. In addition, vapor phase processing is critical for the deposition of insoluble materials including fluoropolymers, electrically conductive polymers, and highly crosslinked organic networks. Furthermore, CVD enables the coating of substrates which would otherwise dissolve or swell upon exposure to solvents. The scope of the book encompasses CVD polymerization processes which directly translate the chemical mechanisms of traditional polymer synthesis and organic synthesis in homogeneous liquids into heterogeneous processes for the modification of solid surfaces. The book is structured into four parts, complemented by an introductory overview of the diverse process strategies for CVD of polymeric materials. The first part on the fundamentals of CVD polymers is followed by a detailed coverage of the materials chemistry of CVD polymers, including the main synthesis mechanisms and the resultant classes of materials. The third part focuses on the applications of these materials such as membrane modification and device fabrication. The final part discusses the potential for scale-up and commercialization of CVD polymers.
The initiated chemical vapor deposition (iCVD) technique is an all‐dry method for designing organic and hybrid polymers. Unlike methods utilizing liquids or line‐of‐sight arrival, iCVD provides ...conformal surface modification over intricate geometries. Uniform, high‐purity, and pinhole‐free iCVD films can be grown with thicknesses ranging from >15 µm to <5 nm. The mild conditions permit damage‐free growth directly onto flexible substrates, 2D materials, and liquids. Novel iCVD polymer morphologies include nanostructured surfaces, nanoporosity, and shaped particles. The well‐established fundamentals of iCVD facilitate the systematic design and optimization of polymers and copolymers. The functional groups provide fine‐tuning of surface energy, surface charge, and responsive behavior. Further reactions of the functional groups in the polymers can yield either surface modification, compositional gradients through the layer thickness, or complete chemical conversion of the bulk film. The iCVD polymers are integrated into multilayer device structures as desired for applications in sensing, electronics, optics, electrochemical energy storage, and biotechnology. For these devices, hybrids offer higher values of refractive index and dielectric constant. Multivinyl monomers typically produce ultrasmooth and pinhole‐free and mechanically deformable layers and robust interfaces which are especially promising for electronic skins and wearable optoelectronics.
Using initiated chemical vapor deposition (iCVD), organic and hybrid thin films can form directly on substrates of virtually any composition and geometry. Free‐radical polymerization of adsorbed monomers is initiated by vapor phase radicals formed by thermal decomposition. The established fundamentals enable the rational optimization of iCVD polymers and copolymers for sensing, optoelectronics, electrochemical energy storage, and biotechnology.
Water repellency is often generated by taking advantage of surface textures and low surface energy coatings such as the one afforded by long perfluorinated side‐chains polymers. However, new ...regulations are phasing out these polymers because of their related health and safety hazard concerns. This is a particular challenge for water‐repellent fabrics as consumers expect safer products with stable performance and new functionalities. In this work, an approach is developed that allows for iCVD deposition of durable, conformal short fluorinated polymers stabilized with a crosslinking agent. As a result, high hydrophobicity and low liquid adhesion are achieved simultaneously while maintaining initial substrate breathability. It is explained why this polymeric coating—1H,1H‐perfluorooctyl methacrylate co divinylbenzene—exhibits remarkable hydrophobic properties amidst a wide range of other possible candidates. In order to further enhance the dynamic water repellency performance, the chemical treatment is combined with physical texturing—obtained through microsandblasting, a process particularly suitable for fabrics—thus making this combined approach a suitable candidate to meet the industrial needs. This work paves the way for the development of environmentally friendly, highly repellent coatings for large volume production and the application of roll‐to‐roll coating techniques, and multifunctionalization of fabrics and wearable devices.
Initiated chemical vapor deposition (iCVD) of conformal short fluorinated polymers stabilized with a crosslinking agent is successfully carried out with 1H,1H‐perfluorooctyl methacrylate crosslinked with divinylbenzene. The ultrathin, grafted, and multifunctionalization aspect of iCVD leads to breathable, low material usage, durable, and EPA acceptable liquid repellent coatings particularly suited for substrates as diverse as fabrics, paper, and nanotextured silicon.
Smooth, durable, ultrathin antifouling layers are deposited onto commercial reverse osmosis membranes without damaging them and they exhibit a fouling reduction. A new synergistic approach to ...antifouling, by coupling surface modification and drinking‐water‐level chlorination is enabled by the films' unique resistance against chlorine degradation. This approach substantially enhances longer‐term fouling resistance compared with surface modification or chlorination alone, and can reduce freshwater production cost and its collateral toxicity to marine biota.
The formation of solid inorganic salts from solutions is of fundamental importance for industrial, geological, and biological processes. Here, we review the literature on the fundamentals of ...inorganic scaling with the goal of elucidating the underlying phenomena observed during thermal desalination processes, mainly multi-stage flash (MSF). We will focus on one of the most common foulants, CaCO3, recognizing that similar phenomena occur for other salts and that behaviors in mixtures with other salts and organic molecules will impact the real world situation. This review will cover a wide range of dimensions, providing views from molecular level to plant scale. In addition to the mechanism and kinetics of scale formation in MSF, we will also review current strategies to control scaling in MSF and highlight directions for future development.
•Heterogeneous nucleation is a key step during scale formation.•In situ characterization methods enable enhanced analysis of nucleation kinetics.•Temperature, pH, CO2 partial pressure and seawater composition all affect scaling.•Key factors for heterogeneous nucleation need more investigation.•Anti-scaling coatings could be effective solutions for scaling control.
Nanocarbon electronic conductors combined with pseudocapacitive materials, such as conducting polymers, display outstanding electrochemical properties and mechanical flexibility. These ...characteristics enable the fabrication of flexible electrodes for energy‐storage devices; that is, supercapacitors that are wearable or can be formed into shapes that are easily integrated into vehicle parts. To date, most nanocarbon materials such as nanofibers are randomly dispersed as a network in a flexible matrix. This morphology inhibits ion transport, particularly under the high current density necessary for devices requiring high power density. Novel flexible densified horizontally aligned carbon nanotube arrays (HACNTs) with controlled nanomorphology for improved ion transport are introduced and combined with conformally coated poly(3‐methylthiophene) (P3MT) conducting polymer to impart pseudocapacitance. The resulting P3MT/HACNT nanocomposite electrodes exhibit high areal capacitance of 3.1 F cm−2 at 5 mA cm−2, with areal capacitance remaining at 1.8 F cm−2 even at a current density of 200 mA cm−2. The asymmetric supercapacitor cell also delivers more than 1–2 orders of magnitude improvement in both areal energy and power density over state‐of‐the‐art cells. Furthermore, little change in cell performance is observed under high strain, demonstrating the mechanical and electrochemical stability of the electrodes.
A novel flexible supercapacitor cell based on densified horizontally aligned carbon‐nanotube arrays combined with a new conducting polymer is developed. The controlled nanomorphology of the nanotube arrays improves the performance of the ion‐transport paths, while the conducting polymer imparts pseudocapacitance. The cell exhibits superior electrochemical performance, including extremely high areal capacitance and excellent capacitance.
Ultra‐thin copolymer films are deposited by initiated chemical deposition (iCVD) to investigate their performance under the condensation of water vapor. By forming a grafted interface between the ...coating and the substrate, the films exhibit stable dropwise condensation even when subjected to 100 °C steam. The applicability of the iCVD to complex substrate geometries is demonstrated on a copper condenser coil.
Electronic conduction in conjugated polymers is of emerging technological interest for high‐performance optoelectronic and thermoelectric devices. A completely new aspect and understanding of the ...conduction mechanism on conducting polymers is introduced, allowing the applicability of materials to be optimized. The charge‐transport mechanism is explained by direct experimental evidence with a very well supported theoretical model.
Antifouling thin films of polyN,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)-co-2-(dimethylamino)ethyl methacrylate-co-ethylene glycol dimethacrylate (PDDE) were synthesized via a ...substrate-independent and all-dry-initiated chemical vapor deposition (iCVD) technique followed by a diffusion-limited vapor-phase reaction with 1,3-propane sultone. Coated surfaces exhibited very low absorption of various foulants including bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), as measured with the quartz crystal microbalance with dissipation monitoring (QCM-D). The fouling by humic acid was dependent on the presence of divalent cations such as Ca2+. Both depth profiling and angle-resolved X-ray photoelectron spectroscopy (XPS) measurements indicated that the zwitterionic groups were highly concentrated in the top ∼3 nm of the film. The contact angle measurements revealed a limited degree of surface chain reorganization upon contacting water. The dynamic contact angles remained unchanged after 100 days of storage in air, indicating the stability of the interface. The coating was substrate-independent, and the film was conformal on surface nanostructures including trenches, reverse osmosis membranes, and electrospun nanofiber mats.
High-aspect ratio hydrophobic, cylindrical nanopores having diameters as low as 5 nm are rapidly fabricated using conformal vapor deposition of fluorinated polymeric layers into porous track-etched ...polycarbonate membranes. The resultant selectivity of these membranes for pairs of small molecules of similar size, but of different hydrophobicity, arises from solute−pore wall interactions emphasized by confinement. Increasing selectivity was observed as pore diameter decreased and as the surface of the pore became more hydrophobic. Cylindrical pores provided higher selectivity than bottleneck-shaped pores having the same minimum diameter. A maximum selectivity of 234 was achieved between mesitylene and phloroglucinol by the best performing membrane. Membranes with small fluorinated pores exhibited an effective cutoff based on the polar surface area of the molecules, with limited correlation with solute size. This technology could lead to a new generation of membrane separations based on specific interactions.
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