Initiated chemical vapor deposition (iCVD) has been shown to be suitable for blanketing surfaces with thin polymer coatings of ≈1–2 nm and greater. In this work, iCVD coatings of polytetrafluoroethylene (PTFE) deposited on carbon nanotube (CNT)‐based surfaces show CNT‐templated PTFE single crystal growth. While the coating forms disoriented agglomerates when deposited on an amorphous carbon background, “shish‐kebab” structures are observed when grown on single‐walled carbon nanotubes (SWCNT) as well as CNT buckypaper. It is shown that the shish‐kebab structure is composed of PTFE lamellae arranged with the chain backbones running parallel to the SWCNT axis. This result allows one to control not only the surface chemistry using PTFE but also the coating surface topology. 相似文献
Initiated chemical vapor deposition (iCVD) is presented as an all-dry synthesis and coating method for applying methacrylic acid copolymers as pH-responsive controlled release layers. iCVD combines the strengths of liquid-phase chemical synthesis with a precision solvent-free chemical vapor deposition environment. Copolymers of methacrylic acid and ethyl acrylate were confirmed by a systematic shift in the carbonyl bond stretching mode with a shift in the comonomer ratio within the copolymer and by the ability to apply the Fineman-Ross copolymerization equation to describe copolymerization kinetics. Copolymers of methacrylic acid and ethylene dimethacrylate showed pH-dependent swelling behavior that was applied to the enteric release of fluorescein and ibuprofen. 相似文献
Click‐active surfaces patterned at 200 nm resolution are demonstrated using the dual functional polymeric film, poly(propargyl methacrylate) (PPMA). The commercially available monomer of propargyl methacrylate (PMA) is polymerized in a single step by initiated chemical vapor deposition (iCVD). FT‐IR and X‐ray photoelectron spectroscopy confirm retention of the click‐active acetylene functional group in the bulk and surface of the iCVD film, respectively. Treating substrates with silane coupling agents prior to deposition results in grafting of iCVD PPMA polymers onto various inorganic surfaces. This grafting technique provides the chemical and mechanical stability required for the PPMA layer to survive the subsequent wet chemical steps used for click functionalization. Successful attachment of an azido‐functionalized coumarin dye is demonstrated. Moreover, the PPMA film displays direct positive‐tone sensitivity to e‐beam irradiation, which enables e‐beam patterning without the use of a resist layer. Direct e‐beam exposure of the multifunctional PPMA iCVD layer results in a 200 nm pattern to which quantum dot nanoparticles are selectively conjugated on the substrates by click chemistry.
A group of crosslinked cyclic siloxane (Si O) and silazane (Si N) polymers are synthesized via solvent‐free initiated chemical vapor deposition (iCVD). Notably, this is the first report of cyclic polysilazanes synthesized via the gas‐phase iCVD method. The deposited nanoscale thin films are thermally stable and chemically inert. By iCVD, they can uniformly and conformally cover nonplanar surfaces having complex geometry. Although polysiloxanes are traditionally utilized as dielectric materials and insulators, our research shows these cyclic organosilicon polymers can conduct lithium ions (Li+) at room temperature. The conformal coating and the room temperature ionic conductivity make these cyclic organosilicon polymers attractive for use as thin‐film electrolytes in solid‐state batteries. Also, their synthesis process and properties have been systemically studied and discussed.
Initiated chemical vapor deposition (iCVD) of alternating copolymer thin films has been achieved for the first time. Copolymerization is desirable for maleic anhydride (Ma) since this monomer does not homopolymerize to an appreciable extent. At conditions where the observed deposition rates for styrene (S) and Ma homopolymers were only 0 and 5.5 nm/min, respectively, combining the two monomers resulted in a much higher deposition rate of 75.4 nm/min. iCVD processes utilize low energy (<30 W) to generate peroxy radicals from initiator molecules while avoiding degradation of functional groups in the monomers. Indeed, full retention of the anhydride functionality from the Ma monomer and avoidance of undesirable side reactions was observed in iCVD of poly(styrene-alt-maleic anhydride) (PSMa) copolymer films. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and 13C nuclear magnetic resonance (NMR) conclusively demonstrate that all of the copolymer films contain 50% styrene and 50% Ma (within experimental error), irrespective of gas feed ratios employed during the deposition. The 13C NMR signal in the 136-140 ppm region from the quaternary carbon in styrene and additional distortionless enhancement polarization transfer experiments confirmed that the copolymers are strictly alternating. Varying the gas feed ratio of Ma to styrene provided control over deposition rates and number-average molecular weights. Number-average molecular weights varied from 1380 to 4680 g/mol, and deposition rates varied from 6.3 to 75.4 nm/min. 相似文献
A solvent-free initiated chemical vapor deposition (iCVD) process was used to create low surface energy poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) thin films at deposition rates as high as 375 nm/min. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy showed full retention of the fluorine moieties, and no measurable cross-linking was detected. Additionally, the FTIR studies support the hypothesis that film deposition results from vinyl polymerization. For all iCVD PPFDA films, the static contact angle was found to be 120.8 +/- 1.2 degrees. The roughness of the films was found to be between 14.9 and 19.8 nm RMS, and the refractive index of the films was found to be between 1.36 and 1.37. The deposition rate was studied as a function of the substrate temperature and the partial pressure of the monomer. It was found that the deposition rate increases with decreasing substrate temperature and increasing monomer partial pressure. It was also found that the molecular weight increases with decreasing substrate temperature and increases with increasing monomer partial pressure. The highest molecular weight measured was 177 300 with a polydispersity of 2.27. Quartz crystal microbalance (QCM) measurements showed that these effects correlated with an increased monomer concentration at the surface. The deposition rate data and the QCM data were quantitatively analyzed to find the rate constants of the process using a previously published model for the iCVD process involving nonfluorinated monomers. The determined values of the rate constants of the surface polymerization were found to be similar to the rate constants measured in liquid-phase free radical polymerization. The kinetic data found in this paper can now be used to study iCVD deposition onto substrates with more complex geometries. 相似文献
Furan ring‐functionalized solid surfaces are achieved by the initiated chemical vapor deposition (iCVD) method, a solvent‐free process to form films under mild conditions. The polymerization of furfuryl methacrylate monomer is initiated by a resistively heated filament wire. The functionality of the furan group in the iCVD film enabled Diels–Alder chemistry with 4‐phenyl‐1,2,3‐triazolin‐3,5‐dione (N‐PTD).
Terpolymers of methyl alpha-chloroacrylate (MCA), methacrylic acid (MAA), and methacrylic anhydride (MAH) were synthesized by initiated chemical vapor deposition (iCVD) of MCA and MAA followed by low-temperature annealing that partially converts MAA into MAH. The MAA composition in the iCVD copolymer can be systematically varied between 37 and 85 mol % by adjusting the gas feed fractions of monomers. Study of the monomer reactivity ratios and the copolymer molecular weights supports the hypothesis of a surface propagation mechanism during the iCVD copolymerization. The carboxylic dehydration reaction at the annealing temperature of 160 degrees C is dominated by a mechanism of intramolecular cyclization, resulting in intramolecular MAH anhydride formation while preventing crosslink formation. The incorporation of highly electron-withdrawing anhydride functionality enhances chain scission susceptibility under electron-beam irradiation. P(MCA-MAA-MAH) terpolymer thin films can be completely developed at dosages as low as 20 microC/cm2 at 50 kV. High-quality positive-tone patterns were created with 60 nm feature size achieved in the vapor deposited films. 相似文献
A reliable screen‐printed sensor for cadmium speciation analysis is presented here. Its development has been focused on the achievement of a reproducible and repeatable sensor. The electrode construction and its surface coating are discussed in detail. The optimized procedure has permitted to obtain very accurate sensors with detection limit of 0.2 μg (Cd) L?1 using SWASV for only 60 s of deposition time. The electrochemically accessible, i.e. potentially bioavailable, fraction of the cadmium present in an untreated river water sample has been successfully quantified without degassing. These results give a glimpse of the potential of this membrane‐free sensor in real matrices. 相似文献
Given its biocompatibility, elasticity, and gas permeability, poly(dimethylsiloxane) (PDMS) is widely used to fabricate microgrooves and microfluidic devices for three-dimensional (3D) cell culture studies. However, conformal coating of complex PDMS devices prepared by standard microfabrication techniques with desired chemical functionality is challenging. This study describes the conformal coating of PDMS microgrooves with poly(N-isopropylacrylamide) (PNIPAAm) by using initiated chemical vapor deposition (iCVD). These microgrooves guided the formation of tissue constructs from NIH-3T3 fibroblasts that could be retrieved by the temperature-dependent swelling property and hydrophilicity change of the PNIPAAm. The thickness of swollen PNIPAAm films at 24 °C was approximately 3 times greater than at 37 °C. Furthermore, PNIPAAm-coated microgroove surfaces exhibit increased hydrophilicity at 24 °C (contact angle θ = 30° ± 2) compared to 37 °C (θ = 50° ± 1). Thus PNIPAAm film on the microgrooves exhibits responsive swelling with higher hydrophilicity at room temperature, which could be used to retrieve tissue constructs. The resulting tissue constructs were the same size as the grooves and could be used as modules in tissue fabrication. Given its ability to form and retrieve cell aggregates and its integration with standard microfabrication, PNIPAAm-coated PDMS templates may become useful for 3D cell culture applications in tissue engineering and drug discovery. 相似文献
The thermodynamics of temperature-responsive polymeric layers was analyzed using a two-state coil to globule model to which the van't Hoff relationship was applied. For soluble homopolymer poly(N-isopropylacrylamide (pNIPAAm), enthalpies of transition, ΔH(vH), were calculated using varations in ultraviolet-visible (UV-vis) spectroscopy with temperature to be 8400 ± 30 and 1652 ± 4 kJ mol-cooperative unit(-1) for standard synthesis and initiated chemical vapor deposition (iCVD), respectively. For the insoluble surface-bound layer of cross-linked iCVD poly(N-isopropylacrylamide-co-di(ethylene glycol) divinyl ether) [p(NIPAAm-co-DEGDVE)], ΔH(vH) was determined to be 810 ± 30 kJ mol-cooperative unit(-1) using quartz crystal microbalance with dissipation monitoring (QCM-D). Microcalorimetry measurements showed the enthalpies per mole NIPAAm monomer to be 5.8 ± 0.2, 3.5 ± 0.6, and 3.1 ± 0.3 kJ mol-NIPAAm(-1), resulting in cooperative unit sizes of 1460 ± 60, 470 ± 80, and 260 ± 30 monomer units for the standard pNIPAAm, iCVD pNIPAAm, and p(NIPAAm-co-DEGDVE) systems, respectively. These values indicate that both per monomer enthalpic contribution as well as cooperative unit size are primary factors contributing to the variations in van't Hoff enthalpies for the three systems studied. Diffusion of bovine serum albumin (BSA) into swollen p(NIPAAm-co-DEGDVE) films below its lower critical solution temperature was elucidated via QCM-D measurements. These data provided a calculated diffusion coefficient of (3.5 ± 0.1) × 10(-14) cm(2) s(-1) of BSA into the swollen hydrogel film with a mesh size of 6.0 ± 0.2 nm (compared to the hydrodynamic radius of BSA, r(H) = 3.36 nm). 相似文献
Epitaixial metal‐oxide nanocomposite films, which possess interesting multifunctionality, have found applications in a wide range of devices. However, such films are typically produced by using high‐vacuum equipment, like pulse‐laser deposition, molecular‐beam epitaxy, and chemical vapor deposition. As an alternative approach, chemical solution methods are not only cost‐effective but also offer several advantages, including large surface coating, good control over stoichiometry, and the possible use of dopants. Therefore, in this Personal Account, we review the chemistry behind several of the main solution‐based approaches, that is, sol‐gel techniques, metal‐organic decomposition, chelation, polymer‐assisted deposition, and hydrothermal methods, including the seminal works that have been reported so far, to demonstrate the advantages and disadvantages of these different routes. 相似文献
The protective coating on mussel (Mytilus galloprovincialis) byssus has attracted considerable research interest because of its excellent mechanical properties such as hardness and extensibility. These special properties are known to be highly related with specific interactions between mussel foot protein‐1 and metal ions. In particular, the complexation between catechols in mfp‐1 and iron(III) has been identified as a key interaction. This finding has given opportunities for pursuing promising applications. Herein, we report that emulating the properties of the mussel byssus cuticle provides an important platform for developing reversible layer‐by‐layer (LbL) deposition, an advanced technique for surface modification. LbL films were constructed on solid substrates by sequential immersion of substrates into solutions containing iron(III) and catecholic compounds. The thickness of the LbL films was effectively controlled by increasing the immersion steps, and the reversibility of the LbL deposition was demonstrated by addition of a chelating agent. 相似文献
Nafion polymer coated bismuth‐film‐modified carbon film electrodes have been investigated for reducing the influence of contaminants such as surfactants in the anodic stripping voltammetry of trace metal ions. The influence of the coating on electrode response has been tested with both ex situ and in situ bismuth film deposition, with and without the polymer coating. The electrode assemblies and interfacial characteristics in the presence of the non‐ionic surfactant Triton‐X‐100 have been probed with electrochemical impedance spectroscopy. The Nafion coating successfully decreases the adsorption of Triton on the bismuth film surface, and demonstrates that this strategy allows measurement of these trace metals in environmental samples containing surfactants. 相似文献
A series of luminescent platinum(II) complexes of tridentate 1,3‐bis(N‐alkylbenzimidazol‐2′‐yl)benzene (bzimb) ligands has been synthesized and characterized. One of these platinum(II) complexes has been structurally characterized by X‐ray crystallography. Their electrochemical, electronic absorption, and luminescence properties have been investigated. Computational studies have been performed on this class of complexes to elucidate the origin of their photophysical properties. Some of these complexes have been utilized in the fabrication of organic light‐emitting diodes (OLEDs) by using either vapor deposition or spin‐coating techniques. Chloroplatinum(II)? bzimb complexes that are functionalized at the 5‐position of the aryl ring, [Pt(R‐bzimb)Cl], not only show tunable emission color but also exhibit high current and external quantum efficiencies in OLEDs. Concentration‐dependent dual‐emissive behavior was observed in multilayer OLEDs upon the incorporation of pyrenyl ligand into the Pt(bzimb) system. Devices doped with low concentrations of the complexes gave rise to white‐light emission, thereby representing a unique class of small‐molecule, platinum(II)‐based white OLEDs. 相似文献