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Applications in soft, flexible optical, and optoelectronic applications demand polymer thin film coatings that can accommodate substantial physical deformations. The preparation of high refractive index polymers (HRIPs) through the quaternization of poly(4‐vinylpyridine) (P4VP) thin films with (di)halomethanes is presented. P4VP thin films are prepared by initiated chemical vapor deposition (iCVD) and then quaternized through exposure to saturated vapors of iodomethane (CH3I), dibromomethane (CH2Br2), and diiodomethane (CH2I2), resulting in refractive indices (RI) as high as 1.67, 1.71, and 2.07, respectively (at 632.8 nm). Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) confirmed the quaternization of pyridine pendant groups on the polymer chain to n‐methylpyridinium with primarily an iodide or bromide counterion, though a minor fraction of polyiodides are also detected. Additionally, these films demonstrate superior thermal stability, retaining their refractive index and thickness after thermal excursions to 200 °C. The halogenated P4VP films exhibit superior mechanical flexibility relative to conventional inorganic coatings (Al2O3 and Ta2O5) and do not fracture at uniaxial tensile strains as high as 10%. This new material chemistry and fabrication approach method may enable advanced optical designs and functionality in a wide range of substrates and device architectures. [ABSTRACT FROM AUTHOR]

Flexible, compliant permeation barrier layers are critically needed in the optics/optoelectronics industry to protect deformable, polymer‐based optical elements, such as those found in variable focus lenses. To address these needs, a transparent and deformable polymeric permeation barrier coating consisting of poly(1H,1H,6H,6H‐perfluorohexyl diacrylate) (pPFHDA) is prepared by initiated chemical vapor deposition. pPFHDA is a highly crosslinked fluoropolymer, which is deposited onto temperature‐sensitive elastomeric membranes at ambient temperature with high uniformity and conformality. This is believed to be the first demonstration of vapor deposition of the PFHDA monomer. Coatings with thicknesses nominally ranging from 200 to 750 nm are prepared and shown to be impermeable to high‐index optical fluid (polyphenyl thioether) over 2 months at 70 °C, which translates to more than 4 year lifespan at room temperature, even after being subjected to 0.26% biaxial strain. Moreover, due to its amorphous nature, the pPFHDA is transparent from wavelengths of 300–1690 nm and also thermally stable to temperatures of 300 °C. These properties should make pPFHDA coating a particularly compelling candidate for flexible optical/optoelectronic devices requiring transparent and compliant barrier layers. [ABSTRACT FROM AUTHOR]

Next-generation, energy-dense, rechargeable lithium batteries require Li metal anodes that provide ten times the specific capacity of state-of-the-art graphite anodes. But, there are many challenges to the successful utilization of Li anodes, including high chemical reactivity and the propensity to deposit into non-dense, high surface area morphologies, which can result in dendritic growth and significant, associated safety hazards, such as short-circuiting and potential combustion of the liquid electrolyte. Solid-state thin film electrolytes have been used to address both of these challenges. In this review, we will provide an overview of thin film battery designs, highlighting the role of thin film electrolytes, lithium phosphorous oxynitride (LiPON) in particular, in enabling highly reversible, efficient cycling of Li metal anodes. We then discuss progress in thin film electrolyte compositions and vacuum deposition processing that has occurred in roughly the past 20 years. It will be shown how these novel electrolyte compositions and processing capabilities have been used to integrate thin film electrolytes with bulk Li metal anodes required for large format energy storage cells, such as those used in consumer electronics and electric vehicles. We end the review with a brief outlook on the outstanding questions and potential future research directions. [ABSTRACT FROM AUTHOR]

A critical challenge associated with the efficient fabrication of solid-state, three-dimensional microbatteries is the synthesis of conformal, solid-state thin film electrolytes. This study presents the synthesis of lithium ion conducting thin film polyelectrolytes based on poly(methacrylic acid-co-ethylene glycol diacrylate) using initiated chemical vapor deposition. These films are transformed to lithium-bearing polyelectrolytes through an H+/Li+ ion exchange reaction in a 1M LiOCH3 solution in methanol. Infrared spectroscopy of the vibrational stretching modes associated with the carbonyl bond in methacrylic acid confirmed that the ion exchange was successful, and quantification by x-ray photoelectron spectroscopy showed that ion exchange was nearly 100% complete. Incorporation of the crosslinking comonomer ethylene glycol diacrylate (EGDA) was necessary for physical stability of the film during the ion exchange process, and four polyelectrolyte compositions with varying crosslinking densities (ethylene glycol diacrylate content) were prepared to understand its role on ionic conductivity. The highest ionic conductivity was achieved in the polymer film with the lowest crosslinking density (9 mol. % EGDA); its conductivity was determined to be 6 × 10−9 S cm−1 at 20 °C and 1 × 10−5 S cm−1 at 100 °C. The activation energy for ionic conductivity was 0.88 eV. Using atomic force microscopy, the surfaces of thin film polyelectrolytes were shown to be continuous, smooth, and pinhole-free, suggesting that these films are suitable for integration into 3D microbatteries. [ABSTRACT FROM AUTHOR]

Abstract: Chemical vapor deposition (CVD) is an attractive technique for the fabrication of high‐quality polymer thin films. The scheme used to initiate polymer chain growth is fundamental to controlling polymer thin film chemistry. A new initiation scheme for polymer CVD utilizing cationic initiation with a strong Lewis acid, TiCl4, in combination with a hydrogen donor, H2O, is presented. This coinitiation scheme results in polystyrene deposition rates of 139 nm min−1, relative to just 34 nm min−1 when TiCl4 is used alone. Characterization by Fourier transform infrared spectroscopy shows that the polymer structures of polystyrene films prepared by conventional solution‐based techniques and cationic CVD are similar. Synthesis of cross‐linked polymer thin films is also demonstrated by depositing poly(divinylbenzene) and showing its insolubility in a range of solvents. The practical utility of these poly(divinylbenzene) films as corrosion resistant coatings is demonstrated. In 1 n HCl, 200 nm thick films on stainless steel increase the polarization resistance by a factor of 44 relative to bare, untreated stainless steel. [ABSTRACT FROM AUTHOR]

Abstract: The ability of initiated chemical vapor deposition to finely tune crosslinking densities in copolymer thin films has been used to develop a functional, reactive hydrogel system. The system consists of poly[maleic anhydride-co-dimethyl acrylamide-co-di(ethylene glycol) divinyl ether] films covalently attached to silicon substrates using the coupling agent 3-aminopropylethoxydimethylsilane. The swelling of the films in water is pH-dependent, with a maximum swelling ratio of 11 at pH=8. The hydrogel was also functionalized with 0.1 M cysteamine solutions in 2-propanol for 30 min to convert 97% of the anhydride functional groups to carboxylic acid and amide functionalities, confirmed by XPS and Fourier transform infrared spectroscopy. The functionalization yielded free thiol groups at the surface, which were used to attach CdSe/ZnS core-shell semiconductor nanoparticles to the hydrogels. [Copyright &y& Elsevier]

Abstract: The ability of initiated chemical vapor deposition (iCVD) to precisely control compositions of polymer thin films has been extended to the deposition of perfectly alternating copolymers of styrene (S) and maleic anhydride (Ma). The driving force for alternation is the electropositive nature of the maleic anhydride monomer complemented by the electronegative character of the styrene monomer. These interactions permit the incorporation of monomers that do not react (or only to a limited extent) via traditional free-radical homopolymerizations. This is seen in iCVD deposition rates of 0 and 5.5 nm/min for poly(styrene) and poly(maleic anhydride) thin films, respectively, when tert-butyl peroxide (TBPO) is used as initiator. Combining styrene and maleic anhydride yields a maximum deposition rate of 75.4 nm/min. At different gas feed ratios of Ma to S, films of identical composition are obtained. XPS survey scans reveal that the carbon to oxygen ratio is 4, in agreement with the predicted alternating structure. Additionally, alternating structures of the copolymers were confirmed using 13C NMR, which reveals triad distributions. The reactivity of the anhydride functionality has been exploited in solventless derivatizations of films with 2-aminoethanethiol. The extent of derivatization is monitored with Fourier transform infrared spectroscopy (FTIR). [Copyright &y& Elsevier]

Abstract: A new “click chemistry” active functional polymer film was directly obtained from a commercially available monomer of propargyl acrylate (PA) via easy, one-step process of initiated chemical vapor deposition (iCVD). Fourier transform infrared (FTIR) spectra confirmed that significant amount of the click-active acetylene functional group was retained after the iCVD process. The degree of crosslinking could be controlled by intentionally adding crosslinker, such as ethylene glycol diacrylate (EGDA) that was polymerized with PA to form click-active, completely insoluble copolymer. The formed iCVD polymers could also be grafted on various inorganic substrates with silane coupling agents. These crosslinking and grafting techniques give iCVD polymers chemical and mechanical stability, which allows iCVD polymers applicable to various click chemistry without any modification of reaction conditions. Pre-patterned iCVD polymer could be obtained via photolithography and an azido-functionalized dye molecule was also successfully attached on iCVD polymer via click chemistry. Moreover, pPA film demonstrated sensitivity to e-beam irradiation, which enabled clickable substrates having nanometer scale patterns without requiring the use of an additional e-beam resist. Direct e-beam exposure of this multifunctional iCVD layer, a 200 nm pattern, and QD particles were selectively conjugated on the substrates via click chemistry. Thus, iCVD pPA has shown dual functionality as of “clickable” e-beam sensitive material. [Copyright &y& Elsevier]

Abstract: Initiated chemical vapor deposition (iCVD) is used for the first time to deposit a non-acrylic carbon-based polymer, polyvinylpyrrolidone (PVP). PVP is known for its hydrophilicity and biocompatibility, and its thin films have found many applications in the biomedical community, one of which is as antibiofouling surfaces. From vapors of 1-vinyl-2-pyrrolidone (VP) and tert-butyl peroxide (TBPO), iCVD produces PVP thin films that are spectroscopically identical to bulk PVP without using any solvents. iCVD works by selectively fragmenting gaseous TBPO with heat to create radicals for initiation of polymerization. This selectivity ensures that the monomer VP does not disintegrate to form species that do not conform to the structure of PVP. Fourier-transform infrared (FTIR), nuclear magnetic resonance, and X-ray photoelectron spectroscopy (XPS) show full retention of the hydrophilic pyrrolidone functional group. Number-average molecular weights range between 6570 and 10,200g/mol. The addition of ethylene glycol diacrylate (EGDA) vapor to the reaction mixture creates a cross-linked copolymer between VP and EGDA. Films with different degrees of cross-linking can be made depending on the partial pressures of the species. Methods for quantifying the relative incorporation of VP and EGDA using FTIR and XPS are introduced. The film with the lowest degree of cross-linking has a wetting angle of 11°, affirming its high hydrophilicity and iCVD''s ability to retain functionality. [Copyright &y& Elsevier]

Safe, energy-dense batteries are needed to power the next generation of flexible, wearable microelectronic devices. Solid-state Li metal thin-film batteries (TFBs) offer compelling performance but their thin film cathodes require high temperature annealing for optimal electrochemical performance, making integration with low-cost, flexible, thermoplastic substrates difficult. In this study, thin film cathodes based on 0.8Li 2 RuO 3 -0.2LiCoO 2 -xLi 2 O (LRCO) are reported for the first time. LRCO thin-film cathodes prepared by radio-frequency (RF) sputtering provide excellent energy storage performance without requiring a thermal annealing step. X-ray diffraction shows that the LRCO is nanocrystalline, and X-ray photoelectron spectroscopy confirms the 4+ and 3+ oxidation states of Ru and Co, respectively. Energy storage performance as a function of the charge potential was investigated via galvanostatic cycling to identify the maximum safe potential to avoid molecular oxygen evolution from the cathode lattice. Nanocrystalline LRCO delivers a discharge capacity of >110 μAh cm−2 μm−1 at 0.3C which compares favorably to the state-of-art LiCoO 2 thin-film cathode at 69 μAh cm−2 μm−1. The feasibility of fabricating and performance on flexible thermoplastic susbstrates is also demonstrated. On polyethylene terephthalate and polyimide susbtrates, the discharge capacity remains >100 μAh cm−2 μm−1 and the capacity retention is 97.5% over 120 cycles in a bent state. [Display omitted] • As-deposited thin-film cathodes based on Li 2 RuO 3 -LiCoO 2 composites were prepared. • It provides high specific capacity and capacity retention over 175 cycles. • It can be prepared on thermoplastic substrates for flexible thin film batteries. [ABSTRACT FROM AUTHOR]