Functional Polymer Thin Films Research Articles

Functional Polymer Thin Films for Establishing an Effective Electrode Interface in Sulfide‐Based Solid‐State Batteries

AbstractSulfide solid electrolytes (SSEs) have garnered significant attention for their high ionic conductivity in the development of all‐solid‐state batteries (ASSBs). However, SSEs face challenges due to poor chemical and electrochemical stability, leading to SE decomposition at the anode, which in turn increases internal resistance and reduces cycle performance. Herein, to address this issue, thin polymer layers are applied to prevent direct contact between the SSE and anode using the initiated chemical vapor deposition process. This method facilitates the uniform coating of eight types of polymers with polar functionalities on indium (In) anodes. Half‐cell tests and X‐ray photoelectron spectroscopy analysis reveals that poly(acrylic acid) and poly((perfluorohexyl)ethyl acrylate), containing ─COOH and C─F bonds respectively, effectively stabilized the In/SSE interface. In full cells assembled with polymer‐coated In and LiNi0.8Co0.1Mn0.1O2 (NCM811), capacity retention show remarkable improvement, achieving 64.8% for In@pAA and 50.7% for In@pC6FA after 100 cycles, compared to 29.0% for bare In. This study provides insights into the interaction between polar bonds in polymers and SSEs, potentially bridging a significant knowledge gap resulting from the significant lack of research investigating the relationship between polymers, one of the primary materials commonly used in ASSBs.

Aggregation states, thermal molecular motion and carrier properties in functional polymer thin films

Aggregation states, thermal molecular motion and carrier properties in functional polymer thin films

Initiated Chemical Vapor Deposition Kinetics of Poly(4-aminostyrene).

Initiated Chemical Vapor Deposition (iCVD) is a free-radical polymerization technique used to synthesize functional polymer thin films. In the context of drug delivery, the conformality of iCVD coatings and the variety of functional chemical moieties make them excellent materials for encapsulating pharmaceutics. Poly(4-aminostyrene) (PAS) belongs to a class of functionalizable materials, whose primary amine allows decoration of the delivery vehicles with biomolecules that enable targeted delivery or biocompatibility. Understanding kinetics of PAS polymerization in iCVD is crucial for such deployments because drug release kinetics in thin-film encapsulation have been shown to be determined by the film thickness. Nevertheless, the effects of deposition conditions on PAS growth kinetics have not been studied systematically. To bridge that knowledge gap, we report the kinetics of iCVD polymerization as a function of fractional saturation pressure of the monomer (i.e., Pm/Psat) in a dual-regime fashion, with quadratic dependence under low Pm/Psat and linear dependence under high Pm/Psat. We uncovered the critical Pm/Psat value of 0.2, around which the transition also occurs for many other iCVD monomers. Because existing theoretical models for the iCVD process cannot fully explain the dual-regime polymerization kinetics, we drew inspiration from solution-phase polymerization and proposed updated termination mechanisms that account for the transition between two regimes. The reported model builds upon existing iCVD theories and allows the synthesis of PAS thin films with precisely controlled growth rates, which has the potential to accelerate the deployment of iCVD PAS as a novel biomaterial in controlled and targeted drug delivery with designed pharmacokinetics.

Kinetics of All-Dry Free Radical Polymerization under Nanoconfinement

Conformal coating of ultrahigh-aspect-ratio nanostructures with functional polymer thin films is highly desirable in many applications, ranging from biosensing to energy storage. Nevertheless, achi...

Plasma‐initiated chemical vapour deposition of organosiloxane thin films: From the growth mechanisms to ultrathin low‐k polymer insulating layers

AbstractThe growth mechanisms of low dielectric constant polymer thin films elaborated from the atmospheric‐pressure plasma‐initiated chemical vapour deposition (AP‐PiCVD) reaction of a cyclic vinyl organosiloxane are experimentally elucidated in this study. The use of ultrashort plasma pulses (ca. 100 ns), as a polymerisation initiator, with long plasma off‐times results in the formation of atomically smooth thin films. The increase of the monomer saturation ratio, PM/Psat, results in an increase in the growth rate and a better retention of the cyclic structure of the monomer, promoting lower dielectric constants. Based on this experimental study, guidelines are provided to determine the optimal process window for the AP‐PiCVD of functional polymer thin films.

Vapor-deposited functional polymer thin films in biological applications.

Functional polymer coatings have become ubiquitous in biological applications, ranging from biomaterials and drug delivery to manufacturing-scale separation of biomolecules using functional membranes. Recent advances in the technology of chemical vapor deposition (CVD) have enabled precise control of the polymer chemistry, coating thickness, and conformality. That comprehensive control of surface properties has been used to elicit desirable interactions at the interface between synthetic materials and living organisms, making vapor-deposited functional polymers uniquely suitable for biological applications. This review captures the recent technological development in vapor-deposited functional polymer coatings, highlighting their biological applications, including membrane-based bio-separations, biosensing and bio-MEMS, drug delivery, and tissue engineering. The conformal nature of vapor-deposited coatings ensures uniform coverage over micro- and nano-structured surfaces, allowing the independent optimization of surface and bulk properties. The substrate-independence of CVD techniques enables facile transfer of surface characteristics among different applications. The vapor-deposited functional polymer thin films tend to be biocompatible because they are free of remnant toxic solvents and precursor molecules, potentially lowering the barrier to clinical success.

Solventless Synthesis and Patterning of UV‐Responsive Poly(allyl methacrylate) Film

AbstractAsymmetric divinyl monomers are attractive candidates for constructing functional polymer thin films owing to their ability to undergo further reactions after polymerization. Here, the first solventless synthesis of poly(allyl methacrylate) (PAMA) film with retention of abundant allyl groups using initiated chemical vapor deposition (iCVD) is reported. It is demonstrated that lower substrate and filament temperatures lead to better allyl retention, while higher temperatures lead to intramolecular cyclization. The retained allyl groups can be further crosslinked under UV light, and the crosslinking degree can be easily tuned by adjusting the exposure time. Patterning of iCVD PAMA films with 20 µm resolution using a TEM grid as photomask is also demonstrated. The reported synthesis method suggests possible solventless incorporation of AMA in thin films as a latent crosslinker or anchoring sites for further functionalization. The solventless patterning can also extend patterning technique to solvent‐sensitive and non‐planar substrates.

Additive Manufacturing of Mechanically Isotropic Thin Films and Membranes via Microextrusion 3D Printing of Polymer Solutions

Polymer extrusion additive manufacturing processes, such as fused filament fabrication (FFF), are now being used to explore the fabrication of thin films and membranes. However, the physics of molten polymer extrusion constrains achievable thin film properties (e.g., mechanical isotropy), material selection, and spatial control of film composition. Herein, we present an approach for fabrication of functional polymer thin films and membranes based on the microextrusion printing of polymer solutions, which we refer to as "solvent-cast printing" (SCP). Constructs fabricated via SCP exhibited a 43% reduction in anisotropy of tensile strength relative to those fabricated using FFF. The constructs fabricated via SCP exhibited a lesser extent of visible layering defects relative to those fabricated by FFF. Further, the swelling dynamics of the films varied depending on the membrane fabrication technique (i.e., SCP vs manual drop casting). The opportunity for expanding material selection relative to FFF processes was demonstrated by printing poly(benzimidazole), a high-performance thermoplastic with high glass-transition temperatures ( Tg ∼ 400 °C). Results from this work indicate that our new approach could facilitate the manufacture of mechanically isotropic thin films and membranes using currently unprintable high-performance thermoplastics.

Initiated Chemical Vapor Deposition: A Versatile Tool for Various Device Applications

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 micro‐structured 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.

Molecule motion at polymer brush interfaces from single‐molecule experimental perspectives

ABSTRACTPolymer brushes have been widely used as functional surface coatings for broad applications including antifouling, energy storage, and lubrications. Understanding the molecule dynamics at polymer brush interfaces is important in unraveling the structure–property relationships in these materials and establishing a new materials design paradigm of novel functional polymer thin films with efficient interfacial transport. By applying modern fluorescence‐based single‐molecule spectroscopic and microscopic techniques, molecule dynamics at varied polymer brush interfaces have been experimentally investigated in recent years. New insights are given to the understandings of some unique and unusual materials properties of polymer brush thin films. This review summarizes some recent studies of molecular diffusion at polymer brush interfaces, highlights some new understandings of the interfacial properties of polymer brushes, and discusses future research opportunities in this field. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 85–103

Spontaneous wrinkling in azlactone-based functional polymer thin films in 2D and 3D geometries for guided nanopatterning

We report a simple, one step process for developing wrinkling patterns in azlactone-based polymer thin films and brushes in 2D and 3D surfaces. The polymer used in this work wrinkles spontaneously upon deposition and solidification on a substrate without applying any external strain to the substrate, with the mode of deposition defining the direction of the wrinkles. Wrinkle formation is shown to occur on a variety of substrates over large areas. We also find that a very thin brush-like layer of an azlactone-containing block copolymer also exhibits wrinkled topology. Given the spontaneity and versatility of wrinkle formation, we further demonstrate two proofs-of-concept, (i) that these periodic wrinkled structures are not limited to planar surfaces, but are also developed in complex geometries including tubes, cones and other 3D structures; and (ii) that this one step wrinkling process can be used to guide the deposition of metal nanoparticles and quantum dots, creating a periodic, nanopatterned film.

Chemical Vapor Deposition for Solvent‐Free Polymerization at Surfaces

AbstractChemical vapor deposition (CVD) methods are a powerful technology for engineering surfaces. When CVD is combined with the richness of organic chemistry, the resulting polymeric coatings, deposited without solvents, represent an enabling technology in many different fields of application. This article focuses on initiated chemical vapor deposition (iCVD), a new technique that utilizes benign reaction conditions to yield conformal and functional polymer thin films. The latest achievements in coating surfaces and 3D substrates with functional materials, and the use of the technique for biotechnology and selective permeation applications are reviewed, and future directions for iCVD technology are discussed.

Functional polymer thin films designed for antifouling materials and biosensors

AbstractPolymer thin films offer a versatile and ubiquitous platform for a wide variety of real-world applications in biomedicine, nanotechnology, catalysis, photovoltaic devices, and energy conversion and storage. Depending on the chemical composition of the polymers and the associated microenvironment, the physicochemical properties (biocompatibility, stability, wettability, adhesion, morphology, surface free energy, and others) of polymer films can be tuned for a specific application through precisely controlled surface synthesis and the incorporation of desirable and responsive functional groups. In this short review, we first summarise the methods most commonly used for the fabrication of polymer thin films. Then we discuss how these polymer thin films can be used in a selection of biomedical applications in antifouling materials and biosensors. Some directions for the rational design of polymer thin films to achieve a specific function or application are also provided.

Surface modification of cell culture carriers: Routes to anhydride functionalization of polystyrene

Physico-chemical and topographical cues allow to control the behavior of adherent cells. Towards this goal, commercially available cell culture carriers can be finished with a laterally microstructured biomolecular functionalization. As shown in a previous study [Biomacromolecules 4 (2003) 1072], the anhydride moiety facilitates a simple and versatile way to protein binding. The present work addresses the technical issue of anhydride surface functionalization of polystyrene, the most common material for cell culture ware. Different approaches based on low pressure plasma, electron beam and ultraviolet light techniques (i.e. maleic anhydride plasma reactions; plasma, electron beam and UV immobilization of functional polymer thin films; grafting of functional polymers to plasma activated surfaces) are introduced and briefly illustrated with examples. Results are characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and ellipsometry. The different routes are compared in terms of technical feasibility and achievable surface properties.

Applications of Neutron Reflectivity to Analyze Surface and Interface Structure of Functional Organic and Polymer Thin Films

Novel applications of neutron reflectivity to the analyses of surface and interface structure of functional organic and polymer thin films utilizing JPARC pulse neutron source were proposed. Typical applications introduced in this note are interfaces of total organic field effect transistors (OFET) and biomaterials/water interfaces.

Fumaryl chloride and maleic anhydride-derived crosslinked functional polymers for nonlinear optical waveguide applications

The synthesis, processing, and characterization of new crosslinked functional polymer thin films derived from fumaryl chloride and maleic anhydride is presented. Experimental data demonstrated that this is a versatile, convenient, and cost-effective method of fabricating ultrastructure crosslinked and functional polymer thin films for potential nonlinear optical (NLO) or other applications where molecular orientation is required. The unsaturated and processable polyester thin films are capable of crosslinking in air to form a hardened lattice under a variety of conditions, including both thermal and photoinitiated crosslinking. The thermal stability of the second harmonic (SHG) signal for a crosslinked NLO thin film was stable at temperatures up to 150°C, which is in contrast to uncrosslinked polymers whose SHG signals typically decreased over 50% below 100°C. Because of the lack of NH/OH groups and their vibrational overtones in the polymer, these crosslinked polyester systems have a great potential for low optical loss applications at 1550 nm communication wavelength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 317–322, 2004

Optical polymer thin films with isotropic and anisotropic nano-corrugated surface topologies.

Light reflection from computer monitors, car dashboards and any other optical surface can impair the legibility of displays, degrade transmission of optical components and in some cases may even pose safety hazards. Antireflective coatings are therefore widely used, but existing antireflection technologies often perform sub-optimally or are expensive to implement. Here we present an alternative approach to antireflection coatings, based on an extension of our photo-aligning and photo-patterning technology for liquid-crystal displays (LCDs) and liquid-crystal polymer films with smooth surfaces to optical polymer films with controlled surface topologies. Nano- and micro-corrugated topologies are shown to result from optically induced monomer phase-separation on the polymer surfaces. The properties of the resulting films make them suitable high-performance and low-cost antireflection coatings for optical components of virtually any size, shape and material. Moreover, the approach can be used to form a wide range of other functional polymer thin films with isotropic as well as anisotropic topologies. For example, films can be produced whose optical birefringence exceeds that of the birefringence of the polymer material itself. These new films can also be used as diffractive thin films, diffusers, and directional reflectors which preserve light polarization, or as substrates for aligning liquid crystals to produce bright, low-power-consumption LCDs with integrated optical functions and memory.

Polymer-based microcavity with photoencoded quadratic nonlinearity

Functional electro-optic polymer thin films embedded in microcavity structures have been poled by an all-optical procedure based on the interference of multiphoton absorption processes. The photoinduced X((2)) tensor was then further addressed at modal resonance for the fundamental wavelength, leading to significant enhancement of the second-harmonic-generation efficiency. An order-of-magnitude enhancement, which is due to electric field resonant conditions inside the microcavity, has been probed by an optical parametric oscillator, in comparison with a single-path thin-film configuration. This configuration opens new perspectives in the realm of nonlinear photonic device processing.