Polymer Nanofilms Research Articles

Colorimetric polymer nanofilm-based time-temperature indicators for recording irreversible changes of temperatures in cold chain

Monitoring and recording subzero temperatures and humidity are essential activities for pharmaceutical, food-beverage, and cold storage industries, as product quality can be hampered during storage and transportation due to temperature disruptions. Traditional electronic subzero time-temperature indicators (TTIs) can be energy-inefficient, fragile, non-recyclable, and susceptible to data breaches and cyber-attacks. Hydrophilic colorimetric polymer nanofilms have been developed as colorimetric temperature and relative humidity (RH) sensors, however, the reversible color-changing behavior of these films significantly limited their application as TTIs, as cannot record temperature changes in the past. Herein, the first colorimetric polymer nanofilm-based TTI for recording an irreversible change of temperatures is reported. This device has shown quick color response in temperature ranges from 23 °C to -30 °C in fewer than 50 s. Remarkably, when the device experiences temperature disruption above a certain threshold time (tth), it shows irreversible color-changing behavior in response to the temperature change from subzero (-30 °C and -15 °C) to room temperature or above. It was demonstrated that tth, from minutes to days, of the TTI device can be precisely tuned by adjusting moisture absorber type and weight, interior RH, and storage temperature. Several field tests have demonstrated good versatility and applicability of the device.

Modulation between capacitor and conductor for a redox-active 2D bis(terpyridine)cobalt(II) nanosheet via anion-exchange

Ionic polymers are intriguing materials whose functionality arises from the synergy between ionic polymer backbones and counterions. A key method for enhancing their functionality is the post-synthetic ion-exchange reaction, which is instrumental in improving the chemical and physical properties of polymer backbones and introducing of the functionalities of the counterions. Electronic interaction between host polymer backbone and guest ions plays pivotal roles in property modulation. The current study highlights the modulation of responses to external electric field in cationic bis(terpyridine)cobalt(II) polymer nanofilms through anion-exchange reactions. Initially, as-prepared chloride-containing polymers exhibited supercapacitor behaviour. Introducing anionic metalladithiolenes into the polymers altered the behaviour to either conductive or insulative, depending on the valence of the metalladithiolenes. This modulation was accomplished by fine tuning of charge-transfer interactions between the bis(terpyridine)cobalt(II) complex moieties and redox-active anions. Our findings open up new avenue for ionic polymers, showcasing their potential as versatile platform in materials science.

Dual-phase microporous polymer nanofilms by interfacial polymerization for ultrafast molecular separation.

Fine-tuning microporosity in polymers with a scalable method has great potential for energy-efficient molecular separations. Here, we report a dual-phase molecular engineering approach to prepare microporous polymer nanofilms through interfacial polymerization. By integrating two micropore-generating units such as a water-soluble Tröger's base diamine (TBD) and a contorted spirobifluorene (SBF) motif, the resultant TBD-SBF polyamide shows an unprecedentedly high surface area. An ultrathin TBD-SBF membrane (~20 nm) exhibits up to 220 times improved solvent permeance with a moderate molecular weight cutoff (~640 g mol-1) compared to the control membrane prepared by conventional chemistry, which outperforms currently reported polymeric membranes. We also highlight the great potential of the SBF-based microporous polyamides for hydrocarbon separations by exploring the isomeric effects of aqueous phase monomers to manipulate microporosity.

A large-dynamic range conductivity-modulated PANI online analysis and sensing platform for ammonia gas detection using coupled optical probing mode

Due to the large-dynamic range and reversible conductivity modulation capability, polyaniline (PANI) shows promising prospects for diverse applications, such as supercapacitors, rechargeable batteries, and electrochromic materials. However, online characterization of the optical properties of the conductive polymer in the infrared band throughout the synthesis and redox state changing processes poses a challenge. Here, we propose and demonstrate an analysis and sensing platform for real-time evaluation of both thickness and the complex refractive index of PANI nanofilm, and employed for ammonia gas concentration sensing. The coupled optical probing mode of tilted fiber Bragg grating (TFBG) as a robust and portable permittivity perception tool is utilized for online perceiving the large-dynamic-range conductivity change of PANI nanofilm. By reproducing the spectral evolution of the probing cladding mode resonance, we introduce a simulation method for analyzing the optical properties of polymer nanofilms within the infrared band. For ammonia gas detection, the sensing platform exhibited continuous and reliable detection within a concentration range of 25–500 ppm, with an optimal film thickness of 156 nm. A good linear response was observed with a sensitivity of up to 5.2 × 10−3 dB/ppm, and a linearity (R2 = 0.9876) with a detection limit of 10 ppm. Our proposed low-cost and large dynamic range conductivity-modulated PANI-TFBG platform for optical properties online analysis and sensing shows potential in environmental monitoring, healthcare, and the biochemical field.

Preclinical evaluation of the individualized approach for chronic non-healing wounds management

Chronic non‑healing wounds (CNHW) are very common and often incorrectly treated, the morbidity and associated costs of chronic wounds management highlight the need to implement wound prevention and treatment concepts. Objective — to evaluate the possibility of different metal nanooxide polymer nanofilms use for CNHW’ local treatment. Materials and methods. The study design is based on evaluation of various types of dressing materials considering their option for use in CNHW local treatment. Samples of biodegradable polymer films (with an optimal composition of gelatin, polyvinyl alcohol, lactic acid, glycerin and distilled water) saturated with nanoparticles of several oxides with expected antibacterial and pro‑regenerative feature — nZnO, nMgO in concentrations of 1%, 5%, and 10% were used in the study of antimicrobial action and substance release profiling. Quarterly ammonium antiseptic decamethoxin 0.02% was used for control. Results. Obtained data shows that polymer based biodegradable films incorporating optimal component composition (gelatin, polyvinyl alcohol, lactic acid and glycerin) enriched with 5% and 10% zinc nanooxide have potent antimicrobial activity against both gram‑positive and gram‑negative microorganisms, the most common causative agents of CNHW’s. The ion release capacity analysis showed that the Zinc impregnated wound‑healing biodegradable polymer film gradually releases the active substance in a time dependent manner, and the nano‑sized particles of nanoZinc oxide are released from the polymer composition faster than ordinary zinc oxide. Conclusions. Complex natural biodegradable polymer based nanofilms are composite materials impregnated with metal nanooxides showing high potential in local treatment of chronic non‑healing wounds. Polymer film with 5% nanoZnO showed up to the 58% higher antimicrobial activity, comparable or exceeding the one of quarterly ammonium compound decamethoxin. Furthermore, nanoZnO impregnated polymer films compared to standard ZnO impregnated polymer films showed up to 63.2% faster substance release profile with rapid and more unified curve.

A microfluidic platform for automatic continuous flow layer‐by‐layer assembly of polymer multilayered nanofilms

AbstractCapillary flow layer‐by‐layer assembly is a microfluidic platform for high throughput preparation and screening of multilayered polymer nanofilms. However, it is time‐consuming and labor‐intensive, since the switching of polyelectrolyte solutions is done manually. As the emergence of flow chemistry and microdevices for artificial intelligence‐based lab automation, an automatic system that can switch polymer solutions and washing liquids is urgently needed for building functional LbL films inside microfluidic devices. Herein, we construct a continuous flow (ConF)‐layer‐by‐layer (LbL) device that can automatically fabricate polymer nanofilms inside a microfluidic device. By including a flow separator and a mixer (a model polyelectrolyte pair), chitosan and carboxymethyl cellulose can be deposited inside a microfluidic device using the ConF‐LbL system. Resulting nanofilms are studied by investigating thickness and surface roughness of the nanofilms and comparing with the other conventional LbL methods. The acid dissolution method was used to compare the differences in stability between nanofilms made from ConF‐LbL and static immersive method in similar conditions. Furthermore, by using one optimized film formulation for coating on the inside walls of a microfluidic chip, we successfully demonstrated the ability of this device to capture cancer cells in whole blood. This ConF‐LbL platform is expected to be a convenient tool to coat functional nanofilms inside microdevices for biomedical and sensor applications.

Fluorinated porous covalent polymer nanofilm assembled sandwich separator: Lithiophilic sites engender uniform Li+ flux towards lithium metal battery

Lithium metal is renowned for its high theoretical specific capacity and extremely low reduction potential. Nevertheless, the repeated breaking/forming of the solid electrolyte interface and uncontrolled growth of lithium dendrites in lithium metal batteries significantly impede their commercial application. In this study, we propose a novel sandwich separator (F-BtTp@PP) composed of fluorinated porous covalent polymer nanofilms (F-BtTp-Nfilm) assembled using roll-to-roll technology. The F-BtTp@PP improves the pore distribution of PP, enhances its resistance to dendrite penetration, and promotes a uniform distribution of lithium ions flux. Furthermore, Fourier-transform infrared spectroscopy and density functional theory calculations confirm the energy affinity. Abundant lithophilic sites and strong electronegative groups effectively control the deposition behavior of lithium ions, resulting in a transfer number of 0.87. This mitigates effectively the occurrence of significant concentration gradients and localized hot-spots during cycles with high current density. The symmetrical cells of F-BtTp@PP Li|Li can maintain a stable cycling voltage of 52.2 mV for 5600 h under a current density of 20 mA cm−2 and capacity density of 10 mAh cm−2. This result robustly demonstrates the exceptional efficiency of F-BtTp@PP, which can be readily scaled up for protecting lithium metal anodes and provides valuable guidance for the design and industrial development of lithium metal batteries with modified separators.

Specific features of epitope-MIPs and whole-protein MIPs as illustrated for AFP and RBD of SARS-CoV-2.

Molecularly imprinted polymer (MIP) nanofilms for alpha-fetoprotein (AFP) and the receptor binding domain (RBD) of the spike protein of SARS-CoV-2 using either a peptide (epitope-MIP) or the whole protein (protein-MIP) as the template were prepared by electropolymerization of scopoletin. Conducting atomic force microscopy revealed after template removal and electrochemical deposition of gold a larger surface density of imprinted cavities for the epitope-imprinted polymers than when using the whole protein as template. However, comparable affinities towards the respective target protein (AFP and RBD) were obtained for both types of MIPs as expressed by the KD values in the lower nanomolar range. On the other hand, while the cross reactivity of both protein-MIPs towards human serum albumin (HSA) amounts to around 50% in the saturation region, the nonspecific binding to the respective epitope-MIPs is as low as that for the non-imprinted polymer (NIP). This effect might be caused by the different sizes of the imprinted cavities. Thus, in addition to the lower costs the reduced nonspecific binding is an advantage of epitope-imprinted polymers for the recognition of proteins.

Characterizing the thickness and temperature dependence of elastic modulus in polymer films using picosecond ultrasonics

Abstract Polymer nanofilms have found extensive applications in fields such as medical science and microelectronics, making the exploration of their mechanical properties highly significant. In this study, we examine the dependency of the out-of-plane elastic modulus of polymer films on both thickness and temperature, utilizing picosecond ultrasonics. Multiple acoustic modes of a polymer film are employed to measure its elastic modulus with heightened precision. Measurements are conducted on samples with different thicknesses and at different temperatures. The results indicate that the modulus of polymer nanofilms strongly depends on both thickness and temperature. For polymethyl methacrylate (PMMA) films with a thickness of less than 81 nm, the modulus determined exhibits a decrement correlating with thickness and is quantifiably inferior to the analogous bulk value. Additionally, as the temperature rises, the elastic modulus declines at clearly varying rates, which are described by two distinct modulus-temperature coefficients.

3D models of molecularly imprinted polymer nanofilms coupled to interdigitated microelectrodes: A physical performance analysis

This work presents the development of three 3D models in COMSOL Multiphysics® to study the performance of sensing platforms based on molecularly imprinted polymer (MIP) nanofilms (∼50 nm thick) deposited on interdigitated microelectrodes (IDMEs). Polypyrrole and glyphosate were selected as the MIP matrix and the target analyte, respectively. A real prototype was tested to adjust the morphological and electrical parameters of the MIP nanofilm. The prototype and the 3D models were evaluated using electrical impedance spectroscopy. Considering the fill factor concept, the percentage relative change in impedance (Δ|Z|Rel) as the target analyte is attached to the MIP nanofilm was estimated. Three zones appear in the impedance spectra, but only two are related to glyphosate incorporation. In both zones, the impedance increases as the glyphosate fills the MIP nanofilm. The glyphosate incorporation modifies the surface area and affects the electrical properties of the MIP nanofilm seen as a whole. The models reproduce the sensing zones and allow studying the predominant factors in each zone and estimating the performance in terms of Δ|Z|Rel. A Δ|Z|Rel as high as 142% was obtained at 100 mHz under saturation, which agrees with experimental results reported with a similar arrangement. These 3D models, as well as the simulation strategy, are useful in interpreting results related to MIP/IDME-based sensors, which are versatile and easy-to-use devices.

Porous Polymeric Nanofilms for Recreating the Basement Membrane in an Endothelial Barrier-on-Chip.

Organs-on-chips (OoCs) support an organotypic human cell culture in vitro. Precise representation of basement membranes (BMs) is critical for mimicking physiological functions of tissue interfaces. Artificial membranes in polyester (PES) and polycarbonate (PC) commonly used in in vitro models and OoCs do not replicate the characteristics of the natural BMs, such as submicrometric thickness, selective permeability, and elasticity. This study introduces porous poly(d,l-lactic acid) (PDLLA) nanofilms for replicating BMs in in vitro models and demonstrates their integration into microfluidic chips. Using roll-to-roll gravure coating and polymer phase separation, we fabricated transparent ∼200 nm thick PDLLA films. These nanofilms are 60 times thinner and 27 times more elastic than PES membranes and show uniformly distributed pores of controlled diameter (0.4 to 1.6 μm), which favor cell compartmentalization and exchange of large water-soluble molecules. Human umbilical vein endothelial cells (HUVECs) on PDLLA nanofilms stretched across microchannels exhibited 97% viability, enhanced adhesion, and a higher proliferation rate compared to their performance on PES membranes and glass substrates. After 5 days of culture, HUVECs formed a functional barrier on suspended PDLLA nanofilms, confirmed by a more than 10-fold increase in transendothelial electrical resistance and blocked 150 kDa dextran diffusion. When integrated between two microfluidic channels and exposed to physiological shear stress, despite their ultrathin thickness, PDLLA nanofilms upheld their integrity and efficiently maintained separation of the channels. The successful formation of an adherent endothelium and the coculture of HUVECs and human astrocytes on either side of the suspended nanofilm validate it as an artificial BM for OoCs. Its submicrometric thickness guarantees intimate contact, a key feature to mimic the blood-brain barrier and to study paracrine signaling between the two cell types. In summary, porous PDLLA nanofilms hold the potential for improving the accuracy and physiological relevance of the OoC as in vitro models and drug discovery tools.

Programmable directional color dynamics using plasmonics

Adaptive multicolor filters have emerged as key components for ensuring color accuracy and resolution in outdoor visual devices. However, the current state of this technology is still in its infancy and largely reliant on liquid crystal devices that require high voltage and bulky structural designs. Here, we present a multicolor nanofilter consisting of multilayered ‘active’ plasmonic nanocomposites, wherein metallic nanoparticles are embedded within a conductive polymer nanofilm. These nanocomposites are fabricated with a total thickness below 100 nm using a ‘lithography-free’ method at the wafer level, and they inherently exhibit three prominent optical modes, accompanying scattering phenomena that produce distinct dichroic reflection and transmission colors. Here, a pivotal achievement is that all these colors are electrically manipulated with an applied external voltage of less than 1 V with 3.5 s of switching speed, encompassing the entire visible spectrum. Furthermore, this electrically programmable multicolor function enables the effective and dynamic modulation of the color temperature of white light across the warm-to-cool spectrum (3250 K–6250 K). This transformative capability is exceptionally valuable for enhancing the performance of outdoor optical devices that are independent of factors such as the sun’s elevation and prevailing weather conditions.

Novel positively-charged bioderived polymer nanofilms for nuclear wastewater decontamination

In this study, we focused on the effective disposal of radioactive wastewater through the development of nanofiltration membranes using biomass materials. We developed functionalized nanofilms using a bio-derived polymer for the decontamination of nuclear wastewater. The synthesis involved a straightforward interfacial polymerization (IP) process, followed by post-functionalization with polyethyleneimine (PEI). We investigated the impact of curdlan self-assembly on membrane separation performance, both pre- and post-IP reaction. Simultaneous self-assembly of curdlan and PEI grafting led to membranes exhibiting superior separation performance. By manipulating PEI molecular weights, we optimized the membranes' physicochemical properties, leading to superior separation efficiency. As a result, exceptional rejections of Co2+, Sr2+, and Cs+ ions were achieved, with rejection rates reaching 95.5 %, 93.7 %, and 92.54 %, respectively. Furthermore, long-term stability experiments validated the membrane's potential for purifying nuclear wastewater. These findings hold promise for the application of biomaterial-based membranes in the treatment of radioactive nuclear wastewater.

Conformation-Induced stiffening effect of crosslinked polymer thin films

Nanoscale polymeric thin films are widely used in diverse modern applications, where a satisfactory mechanical performance is a requirement to their full functionality. The mechanical response of polymer films is strongly affected by the size effects under nanoconfinement; however, the mechanism of such response in terms of molecular configurations and chain conformations has yet to be determined. In this work, we reveal the conformational origin of the stiffening behavior of crosslinked polymeric nanofilms via coarse-grained molecular dynamics and tailored experiments. We find that the biaxial modulus changes follow the alteration of polymer conformations, decoupled from size and thickness. We propose a theory to quantitatively link the elastic properties of the polymers to the distribution of their chain end-to-end distances, predicting a stiffening effect on uncoiled chains. Finally, we use such insight to obtain several PDMS nano-films of the same thickness but with a variability of two orders of magnitudes in their moduli.

Polymer nanofilm mediated photo-assisted growth of gold nanostructures for sensing of drugs

The growing interest in sensing systems based on surface-enhanced Raman scattering (SERS) motivates the development of versatile and eco-friendly methods for the fabrication of nanostructured metallic surfaces. In this study, we report photo-assisted growth of Au nanostructures (NSs) on a ∼7 nm thick film that consists of end-grafted poly(2-vinyl pyridine). The nanofilm plays a key role in the photo-assisted growth of Au NSs with high SERS activity. The structure, crystallinity, and morphology of Au NSs were probed by different analytical techniques. The limit of detection under laser excitation of 532 nm for rhodamine 6 G was 10 nM with an enhancement factor of 6.4 × 105. The sensing of tamoxifen and sulfamethazine drugs was further performed on the Au NSs, showing the application potential of the presented SERS platform.

Interfacially polymerized nanofilms with triptycene moieties and enhanced micropore interconnectivity for highly permselective gas separations

Highly permeable and selective synthetic polymer membranes are attractive for energy-efficient gas separations, while fabricating such membranes with well-defined micropore architecture and interconnectivity remains a significant challenge. We report the design and fabrication of highly crosslinked and microporous polymer nanofilms via engineering the bridged-bicyclic triptycene triamine moieties into the interfacially polymerized networks. The integrated polyamide nanofilms exhibited hierarchical pore structures with finely tuned microporosity (pore size 0.7–1.0 nm), ultramicroporosity (pore size 0.4–0.7 nm), and submicroporosity (pore size < 0.4 nm) and enhanced micropore interconnectivity due to triptycene-induced non-coplanar orientation and configurational free volume in the networks. Consequently, the composite membranes comprising polyamide nanofilms display exceptional gas separation performance for He and H2 recovery with enhanced permeances and selectivities as well as notable plasticization resistance compared to current state-of-the-art highly crosslinked TFC membranes. It is also proved that the microporosity and gas transport properties of the composite nanofilms are highly tailorable by regulating the reaction conditions. Incorporating hierarchical triptycene units with well-defined and interconnected microvoids provides the potential to fabricate highly permselective thin-film composite membranes applicable for various important gas separations.

Structure Characterization of Polymer Nano-Film on the Difference of Lattice Point Compounds

Structure Characterization of Polymer Nano-Film on the Difference of Lattice Point Compounds

Autonomous Interfacial Assembly of Polymer Nanofilms via Surfactant-Regulated Marangoni Instability.

Interfacial polymerization (IP) provides a versatile platform for fabricating defect-free functional nanofilms for various applications, including molecular separation, energy, electronics, and biomedical materials. Unfortunately, coupled with complex natural instability phenomena, the IP mechanism and key parameters underlying the structural evolution of nanofilms, especially in the presence of surfactants as an interface regulator, remain puzzling. Here, we interfacially assembled polymer nanofilm membranes at the free water-oil interface in the presence of differently charged surfactants and comprehensively characterized their structure and properties. Combined with computational simulations, an in situ visualization of interfacial film formation discovered the critical role of Marangoni instability induced by the surfactants via various mechanisms in structurally regulating the nanofilms. Despite their different instability-triggering mechanisms, the delicate control of the surfactants enabled the fabrication of defect-free, ultra-permselective nanofilm membranes. Our study identifies critical IP parameters that allow us to rationally design nanofilms, coatings, and membranes for target applications.

Simple and Fast Pesticide Nanosensors: Example of Surface Plasmon Resonance Coumaphos Nanosensor

Here, a molecular imprinting technique was employed to create an SPR-based nanosensor for the selective and sensitive detection of organophosphate-based coumaphos, a toxic insecticide/veterinary drug often used. To achieve this, UV polymerization was used to create polymeric nanofilms using N-methacryloyl-l-cysteine methyl ester, ethylene glycol dimethacrylate, and 2-hydroxyethyl methacrylate, which are functional monomers, cross-linkers, and hydrophilicity enabling agents, respectively. Several methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) analyses, were used to characterize the nanofilms. Using coumaphos-imprinted SPR (CIP-SPR) and non-imprinted SPR (NIP-SPR) nanosensor chips, the kinetic evaluations of coumaphos sensing were investigated. The created CIP-SPR nanosensor demonstrated high selectivity to the coumaphos molecule compared to similar competitor molecules, including diazinon, pirimiphos-methyl, pyridaphenthion, phosalone, N-2,4(dimethylphenyl) formamide, 2,4-dimethylaniline, dimethoate, and phosmet. Additionally, there is a magnificent linear relationship for the concentration range of 0.1–250 ppb, with a low limit of detection (LOD) and limit of quantification (LOQ) of 0.001 and 0.003 ppb, respectively, and a high imprinting factor (I.F.4.4) for coumaphos. The Langmuir adsorption model is the best appropriate thermodynamic approach for the nanosensor. Intraday trials were performed three times with five repetitions to statistically evaluate the CIP-SPR nanosensor’s reusability. Reusability investigations for the two weeks of interday analyses also indicated the three-dimensional stability of the CIP-SPR nanosensor. The remarkable reusability and reproducibility of the procedure are indicated by an RSD% result of less than 1.5. Therefore, it has been determined that the generated CIP-SPR nanosensors are highly selective, rapidly responsive, simple to use, reusable, and sensitive for coumaphos detection in an aqueous solution. An amino acid, which was used to detect coumaphos, included a CIP-SPR nanosensor manufactured without complicated coupling methods and labelling processes. Liquid chromatography with tandem mass spectrometry (LC/MS-MS) studies was performed for the validation studies of the SPR.

Interfacial Nanoblisters Formed in Water Serving as Freestanding Platforms for Measuring Elastic Moduli of Polymeric Nanofilms.

Polymeric nanofilms have been widely utilized in diverse cutting-edge technologies, yet accurately determining their elastic moduli remains challenging. Here we demonstrate that interfacial nanoblisters, which are produced by simply immersing substrate-supported nanofilms in water, represent natural platforms for assessing the mechanical properties of polymeric nanofilms using the sophisticated nanoindentation method. Nevertheless, high-resolution, quantitative force spectroscopy studies reveal that the indentation test must be performed on an effective freestanding region around the nanoblister apex and meanwhile under an appropriate loading force, to obtain load-independent, linear elastic deformations. The nanoblister stiffness increases with either decreasing its size or increasing its covering film thickness, and such size effects can be adequately rationalized by an energy-based theoretical model. The proposed model also enables an exceptional determination of the film elastic modulus. Given that interfacial blistering is a frequently occurring phenomenon for polymeric nanofilms, we envision that the presented methodology would stimulate broad applications in relevant fields.