A series of high-k, ultrathin copolymer gate dielectrics were synthesized from 2-cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) monomers by a free radical polymerization via a one-step, vapor-phase, initiated chemical vapor deposition (iCVD) method. The chemical composition of the copolymers was systematically optimized by tuning the input ratio of the vaporized CEA and DEGDVE monomers to achieve a high dielectric constant (k) as well as excellent dielectric strength. Interestingly, DEGDVE was nonhomopolymerizable but it was able to form a copolymer with other kinds of monomers. Utilizing this interesting property of the DEGDVE cross-linker, the dielectric constant of the copolymer film could be maximized with minimum incorporation of the cross-linker moiety. To our knowledge, this is the first report on the synthesis of a cyanide-containing polymer in the vapor phase, where a high-purity polymer film with a maximized dielectric constant was achieved. The dielectric film with the optimized composition showed a dielectric constant greater than 6 and extremely low leakage current densities (<3 × 10 A/cm in the range of ±2 MV/cm), with a thickness of only 20 nm, which is an outstanding thickness for down-scalable cyanide polymer dielectrics. With this high-k dielectric layer, organic thin-film transistors (OTFTs) and oxide TFTs were fabricated, which showed hysteresis-free transfer characteristics with an operating voltage of less than 3 V. Furthermore, the flexible OTFTs retained their low gate leakage current and ideal TFT characteristics even under 2% applied tensile strain, which makes them some of the most flexible OTFTs reported to date. We believe that these ultrathin, high-k organic dielectric films with excellent mechanical flexibility will play a crucial role in future soft electronics.

In spite of the huge research interest, ionic polymers could not have been synthesized in the vapor phase because the monomers of ionic polymers contain nonvolatile ionic salts, preventing the monomers from vaporization. Here, we suggest a new, one-step synthetic pathway to form a series of cross-linked ionic polymers (CIPs) in the vapor phase via initiated chemical vapor deposition (iCVD). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) and 4-vinylbenzyl chloride (VBC) monomers are introduced into the iCVD reactor in the vapor phase to form a copolymer film. Simultaneously in the course of the deposition process, the tertiary amine in DMAEMA and benzylic chloride in VBC undergo a Menshutkin nucleophilic substitution reaction to form an ionic ammonium-chloride complex, forming a highly cross-linked ionic copolymer film of p(DMAEMA-co-VBC). To the best of our knowledge, this is the first report on the synthesis of CIP films in the vapor phase. The newly developed CIP thin film is further applied to the surface modification of the membrane for oil/water separation. With the hydrophilic and underwater oleophobic membrane whose surface is modified with the CIP film, excellent separation efficiency (>99%) and unprecedentedly high permeation flux (average 2.32 × 10 L m h) are achieved.

Advances in device technology have been accompanied by the development of new types of materials and device fabrication methods. Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for surface modification using functional thin film. The building of polymeric thin films from vapor phase monomers is highly desirable for the surface modification of thermally sensitive substrates. The precise control of thin film thicknesses can be achieved using iCVD, creating a conformal coating on nano-, and microstructured substrates such as membranes and microfluidics. iCVD allows for the deposition of polymer thin films of high chemical functionality, and thus, substrate surfaces can be functionalized directly from the iCVD polymer film or can selectively gain functionality through chemical reactions between functional groups on the substrate and other reactive molecules. These beneficial aspects of iCVD can spur breakthroughs in device fabrication based on the deposition of robust and functional polymer thin films. This review describes significant implications of and recent progress made in iCVD-based technologies in three fields: electronic devices, surface engineering, and biomedical applications.

where W and L are the channel width and length, respectively, µ sat is the saturation mobility, C i represents the capacitance per unit area of the dielectric layer, and V T is the threshold voltage in OTFT. The µ sat and V T values are closely related to the properties of channel materials and their interfaces. [ 3 ] To increase I DS with a fi xed V G , it is important to make C i high, considering W and L are predetermined factors. The C i of the given dielectric material can be expressed bywhere ε 0 is the permittivity of vacuum, k is the dielectric constant, and d is the thickness of the dielectric layer, respectively. From the Equation ( 2) , it follows that reducing d or increasing k is required for high C i , leading to high I DS . To reduce d , extremely thin dielectric materials such as selfassembled monolayers (SAMs) [ 4 ] and self-assembled nanodielectrics (SANDs) [ 5 ] had been investigated. However, it was not trivial to secure reliable insulating properties of the ultrathin self-assembled layer, since the full coverage of the monolayer dielectric is strongly affected by environmental parameters such as the composition and corrugation of the surface. [ 6 ] Use of polymer electrolyte materials such as ion-gel [ 7 ] had also been attempted as dielectric layers to increase k , thus C i . Although capacitance exceeding 10 µF cm −2 was demonstrated with the ion-gels via suffi cient mobile ions in the electrolyte, low polarization speed, and high gate leakage current ( I G ) hindered the broad use of ion-gel-based gate dielectrics.As far as the gate dielectrics are concerned, polymeric thin fi lms have been considered as ideal candidates, which exhibit a wide range of dielectric constants, [ 8 ] low-temperature processability, mechanical robustness, and cost competitiveness. [ 9 ] However, with only few exceptions, [ 10,11 ] the insulating property of the polymer fi lms degrades severely as the fi lms become thinner. Various crosslinkable polymers including polyimide (PI), [ 12 ] divinyltetramentyldisiloxane-bis-(benzocyclobutene) (BCB), [ 13 ] poly(4-vinylphenol) (PVP), [ 14,15 ] and Cytop [ 10 ] have been suggested to resolve the problem, however, their high crosslinking/curing temperature (generally higher than 200 °C) limits their application to fl exible devices. Also, retaining the device-to-device uniformity of the ultrathin layer while keeping the high insulating property is still challenging.In this regard, to develop ultrathin but highly uniform polymer dielectrics, a vapor-phase initiated chemical vapor deposition (iCVD) is introduced. [ 16 ] The process can deposit various

Fabrication of new antibacterial surfaces has become a primary strategy for preventing device-associated infections (DAIs). Although considerable progress has recently been made in reducing DAIs, current antibacterial coating methods are technically complex and do not allow selective bacterial killing. Here, we propose novel anti-infective surfaces made of a cross-linked ionic polymer film that achieve selective bacteria killing while simultaneously favoring the survival of mammalian cells. A one-step polymerization process known as initiated chemical vapor deposition was used to generate a cross-linked ionic polymer film from 4-vinylbenzyl chloride and 2-(dimethylamino) ethyl methacrylate monomers in the vapor phase. In particular, the deposition process produced a polymer network with quaternary ammonium cross-linking sites, which provided the surface with an ionic moiety with an excellent antibacterial contact-killing property. This method confers substrate compatibility, which enables various materials to be coated with ionic polymer films for use in medical implants. Moreover, the ionic polymer-deposited surfaces supported the healthy growth of mammalian cells while selectively inhibiting bacterial growth in coculture models without any detectable cytotoxicity. Thus, the cross-linked ionic polymer-based antibacterial surface developed in this study can serve as an ideal platform for biomedical applications that require a highly sterile environment.