Polymer Template Research Articles

Preparation of Polymer-Based Nano-Assembled Particles with Fe3O4 in the Core.

Organic-inorganic nanocomposite particles, possessing defined morphologies, represent the next frontier in advanced materials due to their superior collective performance. In this pursuit of efficient preparation of composite nanoparticles, a series of diblock polymers polystyrene-block-poly(tert-butyl acrylate) (PS-b-PtBA) were initially synthesized using the Living Anionic Polymerization-Induced Self-Assembly (LAP PISA) technique. Subsequently, the tert-butyl group on the tert-butyl acrylate (tBA) monomer unit in the diblock copolymer, yielded from the LAP PISA process, was subjected to hydrolysis using trifluoroacetic acid (CF3COOH), transforming it into carboxyl groups. This resulted in the formation of polystyrene-block-poly(acrylic acid) (PS-b-PAA) nano-self-assembled particles of various morphologies. The pre-hydrolysis diblock copolymer PS-b-PtBA produced nano-self-assembled particles of irregular shapes, whereas post-hydrolysis regular spherical and worm-like nano-self-assembled particles were generated. Utilizing PS-b-PAA nano-self-assembled particles that containing carboxyl groups as polymer templates, Fe3O4 was integrated into the core region of the nano-self-assembled particles. This was achieved based on the complexation between the carboxyl groups on the PAA segments and the metal precursors, facilitating the successful synthesis of organic-inorganic composite nanoparticles with Fe3O4 as the core and PS as the shell. These magnetic nanoparticles hold potential applications as functional fillers in the plastic and rubber sectors.

Record Stability for Fully Passive Perovskite‐Based X‐Ray Detectors Through the Use of Starch as Templating Agent

AbstractHigh sensitivity and efficient X‐ray detectors are needed to promote and boost their application as tools in medical diagnostics and radiotherapy. Lead halide perovskites have emerged recently as a novel class of material for efficient X‐ray detection. Although 3D perovskites possess very interesting optoelectronic properties they suffer from low environmental and operational stability. Here a strategy based on using starch as a polymeric template for the fabrication of stable thin film perovskite X‐ray detectors is reported. The proposed p‐i‐n photodiodes can operate with no external bias applied (fully passive devices), reaching a top sensitivity of 5.5 ± 0.2 µC Gy−1 s−1. The device degradation is monitored for samples stored in air for a time window of 630 days, demonstrating exceptional stability: 97% of the initial sensitivity is retained for the best perovskite‐starch composite formulation making it the most stable unencapsulated perovskite X‐ray detector reported so far.

Comparative Study of Porous Iron Foams for Biodegradable Implants: Structural Analysis and In Vitro Assessment.

Biodegradable metal systems are the future of modern implantology. This publication describes the preparation of porous iron-based materials using a simple, affordable replica method on a polymeric template. We obtained two iron-based materials with different pore sizes for potential application in cardiac surgery implants. The materials were compared in terms of their corrosion rate (using immersion and electrochemical methods) and their cytotoxic activity (indirect test on three cell lines: mouse L929 fibroblasts, human aortic smooth muscle cells (HAMSC), and human umbilical vein endothelial cells (HUVEC)). Our research proved that the material being too porous might have a toxic effect on cell lines due to rapid corrosion.

Experimental evidence of a size-dependent sign change of the Seebeck coefficient of Bi nanowire arrays

The electrical transport in bismuth nanowires is strongly influenced by both sample geometry and crystallinity. Compared to bulk bismuth, the electrical transport in nanowires is dominated by size effects and influenced by surface states, which gain increasing relevance with increasing surface-to-volume ratios, i.e. with decreasing wire diameter. Bismuth nanowires with tailored diameter and crystallinity constitute, therefore, excellent model systems, allowing to study the interplay of the different transport phenomena. Here, we present temperature-dependent Seebeck coefficient and relative electrical resistance measurements of parallel bismuth nanowire arrays with diameters between 40 and 400 nm synthesized by pulsed electroplating in polymer templates. Both electrical resistance and Seebeck coefficient exhibit a non-monotonic temperature dependence, with the sign of the Seebeck coefficient changing from negative to positive with decreasing temperature. The observed behavior is size-dependent and is attributed to limitations of the mean free path of the charge carriers within the nanowires. The observed size-dependent Seebeck coefficient and in particular the size-dependent sign change opens a promising avenue for single-material thermocouples with p- and n-legs made from nanowires with different diameters.

Conformal CVD-Grown MoS2 on Three-Dimensional Woodpile Photonic Crystals for Photonic Bandgap Engineering.

To achieve the modification of photonic band structures and realize the dispersion control toward functional photonic devices, composites of photonic crystal templates with high-refractive-index material are fabricated. A two-step process is used: 3D polymeric woodpile templates are fabricated by a direct laser writing method followed by chemical vapor deposition of MoS2. We observed red-shifts of partial bandgaps at the near-infrared region when the thickness of deposited MoS2 films increases. A ∼10 nm red-shift of fundamental and high-order bandgap is measured after each 1 nm MoS2 thin film deposition and confirmed by simulations and optical measurements using an angle-resolved Fourier imaging spectroscopy system.

Qualitative Nanocharacterization of Silver Structures Synthesized from the Reduction of Complex Ions in Polymer Templates: An Inquiry-Based Introduction to Conductive Atomic Force Microscopy

Qualitative Nanocharacterization of Silver Structures Synthesized from the Reduction of Complex Ions in Polymer Templates: An Inquiry-Based Introduction to Conductive Atomic Force Microscopy

From Meso to Macro: Controlling Hierarchical Porosity in Supraparticle Powders.

A drying droplet containing colloidal particles can consolidate into a spherical assembly called a supraparticle. Such supraparticles are inherently porous due to the spaces between the constituent primary particles. Here, the emergent, hierarchical porosity in spray-dried supraparticles is tailored via three distinct strategies acting at different length scales. First, mesopores (<10nm) are introduced via the primary particles. Second, the interstitial pores are tuned from the meso- (35nm) to the macro scale (250 nm) by controlling the primary particle size. Third, defined macropores (>100 nm) are introduced via templating polymer particles, which can be selectively removed by calcination. Combining all three strategies creates hierarchical supraparticles with fully tailored pore size distributions. Moreover, another level of the hierarchy is added by fabricating supra-supraparticles, using the supraparticles themselves as building blocks, which provide additional pores with micrometer dimensions. The interconnectivity of the pore networks within all supraparticle types is investigated via detailed textural and tomographic analysis. This work provides a versatile toolbox for designing porous materials with precisely tunable, hierarchical porosity from the meso- (3nm) to the macroscale (≈10µm) that can be utilized for applications in catalysis, chromatography, or adsorption.

Antibacterial activity of chitosan and zinc oxide impregnated in PVA-based membranes

The development of alternatives to conventional antibiotics against superbugs represents an important step to avoid the increasing resistance of bacteria observed in conventional treatments. Herein, it was evaluated the influence of different combinations of two active antibacterial components (chitosan and zinc oxide) and a host poly (vinyl alcohol - PVA) in membranes produced by the solvent casting technique. Those systems were evaluated in terms of the biofilm inactivation, kill-time assays and inhibition haloes against S. aureus (ATCC 25923) in membranes that must release reactive components while preserving their integrity and favoring the generation of reactive species to improve the antibacterial activity. The results suggest the potential of the combination of chitosan, zinc oxide and poly (vinyl alcohol) to inhibit the growth of S. aureus colonies since the PVA improved the dispersion of the components, whereas chitosan-ZnO chelate improves the mutual activity of the metal oxide and the natural polymer template.

Topologically Triggered Dynamic DNA Frameworks

AbstractTopologically triggered dynamic nucleic acid circuitries play important roles in diverse biological processes. Biomimetic frameworks emulating topologically triggered native circuitries is a challenging topic in the area of Systems Chemistry. Dynamically reconfigurable functions encoded in synthetically engineered nucleic acids provide means to design topologically‐triggered dynamic DNA frameworks. This topic is addressed with three examples: (i) Integration of reconfigurable G‐quadruplex barriers into polymerization or transcription templates leading to the switchable synthesis of a DNAzyme or of an RNA aptamer as models for native gene expression instability processes. (ii) Design of dynamic transient transcription and gated transcription machineries using an autoinhibition reaction module. (iii) Design of dynamic DNA reaction moduli leading to transient biocatalytic cascades, transient aggregation/deaggregation of semiconductor quantum dots or supramolecular Ag nanoclusters.

Cu Nanowire Networks with Well-Defined Geometrical Parameters for Catalytic Electrochemical CO2 Reduction

Three-dimensional, highly interconnected copper nanowire networks are designed and fabricated by electrodeposition in etched ion track polymer templates with interconnected nanochannels and subsequently applied as a catalyst for the electrochemical CO2 reduction toward hydrocarbons and alcohols in an aqueous electrolyte. The specific surface area expressed by the nanowire networks can be adjusted by tailoring the wire length, wire diameter, and nanowire number density to values between 70 cm2 and 300 cm2 per cm2 geometrical sample area. The conversion efficiency and selectivity of CO2 reduction toward liquid- and gas-phase products are studied as a function of the applied potential. Before and after the CO2 reduction reaction, the nanowire networks are characterized by scanning and transmission electron microscopy and by X-ray diffraction, evidencing their stability during CO2 reduction in a potential region between −0.5 V and −0.93 V versus RHE.

PH-Responsive Water-Soluble Chitosan Amphiphilic Core–Shell Nanoparticles: Radiation-Assisted Green Synthesis and Drug-Controlled Release Studies

This work aims to apply water radiolysis-mediated green synthesis of amphiphilic core-shell water-soluble chitosan nanoparticles (WCS NPs) via free radical graft copolymerization in an aqueous solution using irradiation. Robust grafting poly(ethylene glycol) monomethacrylate (PEGMA) comb-like brushes were established onto WCS NPs modified with hydrophobic deoxycholic acid (DC) using two aqueous solution systems, i.e., pure water and water/ethanol. The degree of grafting (DG) of the robust grafted poly(PEGMA) segments was varied from 0 to ~250% by varying radiation-absorbed doses from 0 to 30 kGy. Using reactive WCS NPs as a water-soluble polymeric template, a high amount of DC conjugation and a high degree of poly(PEGMA) grafted segments brought about high moieties of hydrophobic DC and a high DG of the poly(PEGMA) hydrophilic functions; meanwhile, the water solubility and NP dispersion were also markedly improved. The DC-WCS-PG building block was excellently self-assembled into the core-shell nanoarchitecture. The DC-WCS-PG NPs efficiently encapsulated water-insoluble anticancer and antifungal drugs, i.e., paclitaxel (PTX) and berberine (BBR) (~360 mg/g). The DC-WCS-PG NPs met the role of controlled release with a pH-responsive function due to WCS compartments, and they showed a steady state for maintaining drugs for up to >10 days. The DC-WCS-PG NPs prolonged the inhibition capacity of BBR against the growth of S. ampelinum for 30 days. In vitro cytotoxicity results of the PTX-loaded DC-WCS-PG NPs with human breast cancer cells and human skin fibroblast cells proved the role of the DC-WCS-PG NPs as a promising nanoplatform for controlling drug release and reducing the side effects of the drugs on normal cells.

Fabrication of Multifunctional Composite Nanofibers by Green Electrospinning

AbstractThe present work takes advantage of green electrospinning to create novel composite multifunctional nanofibers (NFs) bearing inorganic nanoparticles (NPs), more specifically quantum dots (QDs), cerium oxide nanoparticles (CeO2 NPs) and iron oxide nanoparticles (Fe3O4 NPs). This is achieved by first encapsulating the desired inorganic NPs into polymer particles by the use of miniemulsion polymerization, and second, spinning the hybrid polymer particles using polyvinyl alcohol (PVA) as template polymer. It is proved that using green electrospinning, it is not only possible to ensure an excellent distribution and encapsulation of the inorganic NPs along the NFs, but also allows to control and change the concentration, size, and type of the inorganic NPs without altering the NFs size, a fact that is not possible by conventional solution electrospinning. As proof of concept, NFs with up to three different types of inorganic NPs have been created in a single electrospinning step, but this technology allows to incorporate as much inorganic NPs as desired without altering the NFs morphology and ensuring a good distribution and encapsulation of the NPs. This paper demonstrates that green electrospinning is a powerful and attractive technology to create multifunctional NFs that are promising materials for sensing and biomedical applications.

Popcorn-based dual-monomer copolymerized temperature/pH-sensitive core-shell hydrogels

Temperature/pH-responsive hydrogels are one of the most studied environmental-responsive hydrogels, with sensitivity and rapid response being the sought-after properties, while sensitivity and reusability are generally poor. This study prepared a hydrogel with a temperature/pH-responsive core-shell structure by static template polymerization, using the temperature-sensitive monomer dimethylaminoethyl methacrylate polymerized with 2-acrylamide-2-methylpropanesulfonic acid as the temperature-sensitive shell and popcorn with acrylic acid as the pH-responsive core-layer hydrogel. The chemical structure, thermal stability, and morphology of the core-shell structure hydrogels were characterized by Infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller surface (BET), Scanning electron microscopy (SEM), Atomic force microscopy (AFM) and Thermogravimetric analysis (TG), respectively. The pH responsiveness well as the temperature responsiveness of the shell structure was tested. The results showed that the lowest critical solution temperature (LCST) of the core-shell hydrogel is 43 ℃, with good temperature responsiveness in the range of 25–55 ℃, pH responsiveness from pH= 4 to pH= 13, and a short response time. From SEM, AFM, and BET, it can be concluded that the hydrogel has a rough surface and pore structure with a root mean square roughness value of 0.787 nm, a specific surface area of 1.3381 m²/g, and an average pore size of 4.0911 nm. FTIR and XRD can show that popcorn (PCP) is well-doped in the core-shell structure hydrogel, which also proves the existence of the core-shell structure. The design of the core-shell structure enhanced the stability performance of the shell temperature-sensitive hydrogel so that the retention rate of the sample was still 37% at 800 °C, and the water retention rate was still 80.7% after repeated immersion in distilled water 7 times, which has good prospects for agricultural and pharmaceutical applications.

Synthesis of molecularly imprinted polymer based on cooperative imprinting for enrichment of gallic acid in Puer tea

AbstractThe molecularly imprinted polymer (MIP) for gallic acid (GA) was prepared based on the cooperative imprinting of boronate affinity interactions and hydrogen bond. The fabricated MIP were designed by the polymerization of template with co‐functional monomer, 3‐acrylamidophenylboronic acid (AAPBA) and methacrylic acid (MAA). The characteristics of the resulting polymer (AAPBA‐co‐MAA MIP) were tested by scanning electron microscope (SEM), Fourier transform infrared spectra (FTIR) and nitrogen adsorption–desorption. Bonding performance demonstrated that the AAPBA‐co‐MAA MIP possessed the excellent recognition ability in the incubation solution with pH 7.4 and presented higher adsorption capacity, faster adsorption rate and satisfactory selectivity for GA. Additionally, the AAPBA‐co‐MAA MIP revealed the good applications in the separation and enrichment of GA from Puer tea, and the amount of GA enriched by them was determined to be 2.75 mg g−1. This work suggested that the integration of cooperative imprinting strategy between covalent and non‐covalent would be an effective way to improve the specific recognition performance of the MIP.

Influence of ceramic Kelvin Cell's strut shape on mechanical properties

The replica technique is one of the most established manufacturing methods of highly porous scaffolds for bone tissue engineering. Despite a multitude of possible templates, this method is limited in terms of reproducibility and periodicity. We overcome this issue by 3D-printing of designed periodic polymer templates with varying strut shape and thickness which we further process with the replica technique to obtain cellular ceramics with adjustable micro- and macrostructure. The periodic structure (Kelvin cells) was created using computer-aided design (CAD) software. These 3D rigid polymer structures were coated with alumina slurry and transformed to ceramic structures. This combination of polymer 3D-printing and the replica technique enables the application-specific production of cellular structures in a flexible and cost-effective process.

Covalent nanoarchitectonics: Polymer synthesis with designer structures and sequences

AbstractAs a post nanotechnology concept, nanoarchitectonics integrates nanotechnology with the other research fields to create new functional materials from nanounits, where polymer chemistry plays indispensable roles. In this perspective article, we showcase and discuss about recent and past hot examples on polymer synthesis with sequence and/or structure regulations, including one dimensional sequential polymer of man‐made structures and bio‐related structures, multidimensional polymers through supramolecular templating polymerization and polymerization based on crystals and liquid crystals, and covalent organic framework.

Stimulus-Responsive Ultrathin Films for Bioapplications: A Concise Review.

The term "nanosheets" has been coined recently to describe supported and free-standing "ultrathin film" materials, with thicknesses ranging from a single atomic layer to a few tens of nanometers. Owing to their physicochemical properties and their large surface area with abundant accessible active sites, nanosheets (NSHs) of inorganic materials such as Au, amorphous carbon, graphene, and boron nitride (BN) are considered ideal building blocks or scaffolds for a wide range of applications encompassing electronic and optical devices, membranes, drug delivery systems, and multimodal contrast agents, among others. A wide variety of synthetic methods are employed for the manufacturing of these NSHs, and they can be categorized into (1) top-down approaches involving exfoliation of layered materials, or (2) bottom-up approaches where crystal growth of nanocomposites takes place in a liquid or gas phase. Of note, polymer template liquid exfoliation (PTLE) methods are the most suitable as they lead to the fabrication of high-performance and stable hybrid NSHs and NSH composites with the appropriate quality, solubility, and properties. Moreover, PTLE methods allow for the production of stimulus-responsive NSHs, whose response is commonly driven by a favorable growth in the appropriate polymer chains onto one side of the NSHs, resulting in the ability of the NSHs to roll up to form nanoscrolls (NSCs), i.e., open tubular structures with tunable interlayer gaps between their walls. On the other hand, this review gives insight into the potential of the stimulus-responsive nanostructures for biosensing and controlled drug release systems, illustrating the last advances in the PTLE methods of synthesis of these nanostructures and their applications.

Macroscale Fabrication of Lightweight and Strong Porous Carbon Foams through Template-Coating Pair Design.

Manufacturing of low-density-high-strength carbon foams can benefit the construction, transportation, and packaging industries. One successful route to lightweight and mechanically strong carbon foams involves pyrolysis of polymeric architectures, which is inevitably accompanied by drastic volumetric shrinkage (usually >98%). As such, a challenge of these materials lies in maintaining bulk dimensions of building struts that span orders of magnitude difference in length scale from centimeters to nanometers. This work demonstrates fabrication of macroscale low-density-high-strength carbon foams that feature exceptional dimensional stability through pyrolysis of robust template-coating pairs. The template serves as the architectural blueprint and contains strength-imparting properties (e.g., high node density and small strut dimensions); it is composed of a low char-yielding porous polystyrene backbone with a high carbonization-onset temperature. The coating serves to imprint and transcribe the template architecture into pyrolytic carbon; it is composed of a high char-yielding conjugated polymer with a relatively low carbonization-onset temperature. The designed carbonization mismatch enables structural inheritance, while the decomposition mismatch affords hollow struts, minimizing density. The carbons synthesized through this new framework exhibit remarkable dimensional stability (≈80% dimension retention; ≈50% volume retention) and some of the highest specific strengths (≈0.13GPa g-1 cm3 ) among reported carbon foams derived from porous polymer templates.

Polypeptide Chain Growth Mechanisms and Secondary Structure Formation in Glycine Gas-Phase Deposition on Silica Surfaces.

Peptide formation by amino acids condensation represents a crucial reaction in the quest of the origins of life as well as in synthetic chemistry. However, it is still poorly understood in terms of efficiency and reaction mechanism. In the present work, peptide formation has been investigated through thermal condensation of gas-phase glycine in fluctuating silica environments as a model of prebiotic environments. In-situ IR spectroscopy measurements under a controlled atmosphere reveal that a humidity fluctuating system subjected to both temperature and water activity variations results in the formation of more abundant peptides compared to a dehydrated system subjected only to temperature fluctuations cycles. A model is proposed in which hydration steps result in the hydrolysis and redistribution of the oligomers formed during previous deposition in dry conditions. This results in the formation of self-assembled aggregates with well-defined secondary structures (especially β-sheets). Upon further monomers feeding, structural elements are conserved in newly growing chains, with indications of templated polymerization. The structural dynamics of peptides were also evaluated. Rigid self-assembled structures with a high resistance to further wetting/drying cycles and inaccessibility to isotopic exchange were present in the humidity fluctuating system compared to more flexible structures in the dehydrated system. The resistance and growth of self-assembled structures were also investigated for an extended duration of Gly deposition using isotope labeling.

Probe-impregnated monolithic polymer as a robust solid-state colorimetric chemosensor for selective sensing of Hg2+ in environmental water and cigarette samples

The current study developed a novel aqua-compatible and naked-eye portable solid-state opto-sensor for selective and sensitive detection of ultra-trace Hg2+ ions. The developed chemosensor was fabricated by the direct impregnation of a chromoionophoric probe composed of 2,3-bis((4-isopropylbenzylidene)amino)maleonitrile (PDPM) onto the surface of structurally tailored porous polymer monolithic framework. The template exhibited a highly porous network with greater surface area, which led to the effective anchoring of probe molecules onto the surface of the polymer template, thus serving as an efficient platform to constitute a regenerative solid-state chemosensor. The sensor rendered a superior color shift from dull white to dijon yellow after complexing with Hg2+. The surface, structural, and morphological aspects of the sensor were evaluated using FE-SEM, HR-TEM, EDAX, SAED, p-XRD, N2 adsorption isotherm, and XPS. Rigorous optimization of the effects of different analytical parameters on the sensing performance of the PDPM sensor material was ensured. The monolithic sensor had an optimum sensing performance at pH 8.0, rapid signal response kinetics of 60s and a broad linear response range of 0.5–150.0 μg/L with a 0.22 μg/L detection limit. Furthermore, the sensor was also tolerant of foreign matrix constituents, thereby enabling it to be highly selective in detecting Hg2+. Sensor recovery was analyzed to be possible via Hg2+ desorption using 0.01 M EDTA without compromising its sensing performance. It had reutilization potential for up to eight regenerative cycles with excellent data reliability (recovery ≥99.4% and RSD ≤1.4%). The practicability of the fabricated sensor was investigated using various water and cigarette samples. Experimental data revealed that the developed chromoionophoric sensor was reusable, eco-friendly, low-cost, and possessed superior sensing capabilities, making it more feasible for on-site analysis of environmental samples. The designed sensor has the potential for further investigations and applications as a sensor kit for facilitating heavy metal detection in remote places.