The effect of 3‐glycidoxypropyltrimethoxysilane (GOPS) content in poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) dispersions on the properties of films spun cast from these formulations is investigated. It has been found out that the concentration of GOPS has a tremendous, yet gradual impact on the electrical, electrochemical, and mechanical properties of the PEDOT:PSS/GOPS films and that there is an optimum concentration which maximizes a particular feature of the film such as its water uptake or elasticity. The benefits of aqueous stability and mechanical strength with GOPS are to be compensated by an increase in the electrochemical impedance. GOPS aids obtaining excellent mechanical integrity in aqueous media with still highly conducting properties. Moreover, active devices like organic electrochemical transistors that contain 1 wt% GOPS, which is a concentration that leads to film with high electrical conductivity with sufficient mechanical stability and softness, exhibit steady performance over three weeks. These results suggest that variations in the concentration of such an additive like GOPS can enable a facile co‐optimization of electrical and mechanical properties of a conducting polymer film for in vivo bioelectronics application.
A novel method of preparing skinned asymmetric membranes with two distinctive layers is described: a top layer composed of chemically cross‐linked polymer chains (dense layer) and a bottom layer of non‐cross‐linked polymer chains (porous substructure). The method consists of two simple steps that are compatible with industrial membrane fabrication facilities. Unlike conventional processes to prepare asymmetric membranes, with this approach it is possible to finely control the structure and functionalities of the final membrane. The thickness of the dense layer can be easily controlled over several orders of magnitude and targeted functional groups can be readily incorporated in it.
The ability to fabricate high‐quality colloidal photonic crystal (CPC) films in large areas is critical in many applications, ranging from flexible displays, security devices to optical enhancement. Herein, a large‐scaled CPC film with crack‐free structure and uniform optical performance is prepared via a hydrogen‐bond‐assisted method. The crack‐free CPC film is ascribed to the intermolecular hydrogen bonds between carboxyl ( COOH) moieties of poly(styrene‐methyl methacrylate acrylic acid) microspheres and isocyanate ( NCO ) moieties of polyurethane. Furthermore, the as‐prepared CPC film is applied as a Bragg reflection mirror for fluorescence enhancement. It is demonstrated that a fourfold enhancement of fluorescence signal is achieved when the stopband of CPCs overlaps with the emission wavelength of quantum dots. This simple method of preparing large‐area and crack‐free CPC film is promising for developing efficient optical devices.
For major advances in microfabricated drug delivery systems (DDS), fabrication methods with high throughput using biocompatible polymers are required. Once these DDS are fabricated, loading of drug poses a significant challenge. Here, hot punching is presented as an innovative method for drug loading in microfabricated DDS. The microfabricated DDS are microcontainers fabricated in photoresist SU‐8 and biopolymer poly‐l ‐lactic‐acid (PLLA). Furosemide (F) drug is embedded in poly‐ε‐caprolactone (PCL) polymer matrix. This F‐PCL drug polymer matrix is loaded in SU‐8 and PLLA microcontainers using hot punching with >99% yield. Thus, it is illustrated that hot punching allows high‐throughput, parallel loading of 3D polymer microcontainers with drug‐polymer matrices in a single process step.
A series of drawn melt‐crystallized linear polyethylenes (LPEs) with different molecular weight distributions (MWD = M w/M n) ranging from 2 to 25 are investigated with respect to the visible‐light transparency. The results indicate that the MWD of the LPEs significantly influences the visible‐light transparency of drawn melt‐crystallized LPEs. At a high MWD, drawn melt‐crystallized LPEs films are transparent and glass‐like, this in contrast to the LPEs with a low MWD. A mechanism behind the observed results is proposed based on differential scanning calorimetry (DSC) analysis, small‐angle X‐ray scattering, wide‐angle X‐ray scattering, and small‐angle light scattering experiments. A correlation between the molecular characteristics, especially the MWD, and the visible‐light transparency of the drawn melt‐crystallized LPEs is proposed.
Development of artificial soft materials that have good mechanical performances and autonomous healing ability is a longstanding pursuit but remains challenging. This work reports a kind of highly flexible, tough, and self‐healable poly(acrylic acid)/Fe(III) (PAA/Fe(III)) hydrogels. The hydrogels are dually cross‐linked by triblock copolymer micelles and ionic interaction between Fe(III) and carboxyl groups. Due to the coexistence of these two cross‐linking points, the resulting PAA/Fe(III) hydrogels are tough and can be flexibly stretched, bent, knotted, and twisted. The hydrogels can withstand a deformation of 600% and an ultimate stress as high as 250 kPa. Moreover, the dynamic ionic interaction also endows the hydrogels self‐healing properties. By varying the ratio of Fe(III)/AA, a compromised healing efficiency of 73% and an ultimate stress of 200 kPa are obtained.
An efficient strategy for engineering nanostructured surfaces by coupling soft polymeric nanoarchitectures to functionalized surfaces is presented. Self‐assembly of polymeric nanoarchitectures from amphiphilic triblock copolymers can yield both filled and hollow spherical nanoarchitectures, depending on the properties of the polymer chosen. These nanoarchitectures are immobilized on solid substrates via a biocompatible thiol–ene reaction, and conditions are optimized to maintain structural integrity of polymeric assemblies. Two routes of surface modification are also implemented to allow inclusion of a polymeric spacer that can mediate between soft polymeric assemblies and solid substrates. Nanostructured surfaces with both filled and hollow nanoarchitectures attached to the surface directly or with a spacer are successfully generated with this protocol. This concept of generating nanostructured surfaces using preassembled polymeric architectures is an important step toward active surfaces, because entrapment of active molecules in the nanoarchitectures prior to their immobilization opens the door to easy generation of surfaces with predetermined activities.
The potential of polymerization in a dispersed system as an attractive technique for polymer/graphene composite synthesis is discussed. This overview is focused on the preparation of graphene/polymer composite materials by two methods: (i) emulsion mixing or blending of polymer and graphene aqueous dispersions, and (ii) in situ polymerization in a dispersed system (emulsion, miniemulsion, microemulsion, and Pickering‐stabilized emulsion). Various methods for the stabilization of graphene nanoplatelets (GNPs) prior to composite preparation are presented, and the established specific interactions between the filler and the matrix are discussed. The determination of the electrical conductivity and the opportunity offered by polymerization in a dispersed system for the formation of a segregated network of graphene filler in the frame of a polymer matrix are presented. The mechanical and thermal properties of the composites are also discussed. A short summary of the open questions regarding the synthesis of water‐borne polymer/graphene composites is presented.
Pretreatment coatings applied to metals are essential in the overall performance of anticorrosion coating systems. Hexavalent chromium, a widely used pretreatment for aluminum is now considered harmful. Therefore, a need for environment‐friendly yet efficient and scalable pretreatment coatings has emerged. Here, the authors present the spray‐assisted layer‐by‐layer (LbL) assembly and anticorrosion performance of a highly ordered polymer–clay nanocomposite coating. This approach is an entirely water‐based process, allowing for application over large surface areas. This novel pretreatment coating (25 wt% clay) presents a brick‐and‐mortar multilayered structure, where the montmorillonite clay (MMT) acts as a physical oxygen barrier, while preventing the dissolution of corrosion products—thus delaying corrosion. The branched polyethylenimine polymer (BPEI) mortar provides surface buffering once the corrosion process initiates. The anticorrosion properties of the LbL coating are evaluated using electrochemical measurements and salt‐spray testing. This BPEI/MMT system presents good anticorrosion properties, making it a potential alternative pretreatment.
A novel high purity dual‐functional epoxy monomer, diglycidyl ether of 4,4′‐diallyl‐bisphenol‐A, is deliberately designed for the construction of a fishbone‐shaped heterochain polymer by polymerizing it with the methyl phenyl polysiloxane. Their curing reactions with Jeffamine D230 are investigated. The cured fishbone‐shaped heterochain polymer presents a wide transition range spanning over 120 °C with a peak half‐width of 62 °C. In contrast to the traditional epoxy/polysiloxane materials, the cured fishbone‐shaped heterochain polymer takes full advantage of the cooperative effect of epoxy and polysiloxane exhibiting excellent damping properties (tan δ > 0.3) at temperatures near the T g of the polysiloxane. This outstanding low‐temperature damping performance can be ascribed to the fishbone‐shaped structure of the heterochain polymer. These results provide new approach to explore high damping materials used at extremely low temperature (−125 °C).
Additive manufacturing (AM) is still underutilized as an industrial process, but is quickly gaining momentum with the development of innovative techniques and materials for various applications. In particular, stereolithography (SLA) is now shifting from rapid prototyping to rapid manufacturing, but is facing challenges in parts performance and printing speed, among others. This review discusses the application of SLA for polymer nanocomposites fabrication to show the technology's potential in increasing the applicability of current SLA‐printed parts. Photopolymerization chemistry, nanocomposite preparation, and applications in various industries are also explained to provide a comprehensive picture of the current and future capabilities of the technique and materials involved.
Poly(ethylene glycol) diacrylate (PEG‐DA) hydrogels have been widely utilized to investigate cell–material interactions and as scaffolds for tissue engineering. Traditionally, PEG‐DA hydrogels are prepared via the UV‐cure of aqueous precursor solutions, but afford a limited range of pore size and interconnectivity that is essential for cellular proliferation and neotissue formation. To overcome these limitations, macroporous PEG‐DA hydrogels are prepared in this study using a combination of solvent‐induced phase separation (SIPS) and a fused salt template. PEG‐DA concentration in the organized fabrication solvent (20, 30, and 40 wt%) and average salt particle size (≈180, ≈270, and ≈460 μm) are varied and the resulting hydrated hydrogel morphology, swelling, mechanical properties, and degradation are characterized. These templated SIPS PEG‐DA hydrogels broaden PEG‐DA hydrogel properties and, in some cases, afford a series of compositions whose properties are decoupled.
Although graphene‐based materials have been used as fillers in polymer nanocomposites, a deleterious trade‐off in mechanical strength and ductility is typically observed with increasing graphene loading, resulting in strong but brittle polymer nanocomposite materials. To provide outstanding compatibility with a standard high strength polymer, thermoplastic polyurethane (TPU), the use of a simple and mild sol‐gel reaction to chemically attached silica nanoparticles to graphene oxide (GO) basal plane is reported. The silica modification imparts a highly porous GO surface structure, providing noncovalent attachment sites that improve physical entanglement between the GO and TPU. Furthermore, the silica modification enhances surface polarity, which imparts chemical affinity between the silica/GO nanocomposite and TPU. As a result, the prepared polymer nanocomposites exhibit significantly improved Young's modulus and tensile strength with only a small reduction of elongation at break over the neat polymer.
Assembly of anisotropic nanoparticles on polymeric templates has attracted much attention recently because of the potential useful applications. In this work, 3D electrospun nanofiber membrane is used as template for the assembly of ex situ synthesized palladium nanocubes. The assembly process is achieved by simple immersion step, in which the electrostatic assembly of the nanocubes occurs. The dense nanocubes on the nanofibers as well as the fibrous nanostructure render the nanocomposite membrane excellent catalytic activity. Moreover, the catalytic membrane can be recycled for at least six times, which makes it possible for practical usage.
Polyurethane hydrogel foams synthesized through a facile one‐pot, solvent‐free process are described. The roles of polyethylene glycol (PEG) molecular weight, crosslinking density, and foam stabilizer concentration on polymer properties are evaluated for potential applications as wound dressing materials. Material characterization and wound dressing relevant performance evaluations are performed to understand effects of individual components and identify promising formulations. Surprisingly for a solvent‐free reaction, complete polymerization is confirmed by IR and gel fraction analyses. Foam stabilizing agent loading increases mechanical properties including Young's modulus, extensibility, and toughness while decreasing pore size and drug release rate. Mechanical properties are also dependent on the crystalline melting temperature of the PEG diol. Utilizing caffeine as a drug surrogate, high performance liquid chromatography (HPLC) drug‐release analysis identifies that polyurethane hydrogel foams exhibit initial burst release kinetics followed by sustained release over 24 h. Antibiotic compatibility and release is demonstrated for all formulations by zone of inhibition testing against gram‐positive and negative bacteria.
The N‐containing conjugated microporous polymers (CMPs) are synthesized by 2,5‐dibromopyrazine or its isomeric pyridazine monomer and 1,3,5‐triethynylbenzene via the Pd(0)/Cu(I)‐catalyzed Sonogashira–Hagihara cross‐coupling polycondensation. The resulting CMPs exhibit diverse porosity and morphology, which reveals macroscopically porous 3D networks for BQCMP‐1, agglomerated and amorphous structure for DQCMP‐1, arising from the variation of isomeric monomer. In addition, metal ions adsorption capacity of Zn(II), Cr(VI), Ni(II) have been investigated due to the good porosity of CMPs. Compared with Zn(II) and Cr(VI), the adsorption capacity of Ni(II) for BQCMP‐1 and DQCMP‐1 is maximal, which is 272 mg g?1 and 559 mg g?1. Our study may provide a useful guidance to manipulate CMPs by varying the constitution of isomeric monomer.
Polymerization shrinkage of dental composites remains a major concern. Free‐radically polymerizable cyclic monomers can be a conceivable alternative to methacrylates for the development of low‐shrinkage composites. In this study, the one‐step synthesis of the novel low viscosity difunctional vinylcyclopropanes 1 – 4 is described. Photopolymerization kinetics of these monomers are investigated by photo‐differential scanning calorimeter, using bis(4‐methoxybenzoyl)diethylgermane as photoinitiator. Real‐time near‐infrared photorheology measurements are performed to evaluate rheological behavior (i.e., time of gelation, polymerization‐induced shrinkage force) and chemical conversion (i.e., double bond conversion at the gel point, final double bond conversion) of the vinylcyclopropanes in situ. The potential of these monomers as reactive diluents in dental restorative materials is evaluated. Composites based on vinycyclopropanes 1 – 4 show good mechanical properties and exhibit significantly lower volumetric shrinkage and shrinkage stress than corresponding dimethacrylate‐based materials. The results indicate that such monomers are promising candidates for the replacement of commonly used low viscosity dimethacrylates such as triethylene glycol dimethacrylate in dental composites.
Nanofiber production platforms commonly rely on volatile carrier solvents or high voltages. Production of nanofibers comprised of charged polymers or polymers requiring nonvolatile solvents thus typically requires customization of spinning setup and polymer dope. In severe cases, these challenges can hinder fiber formation entirely. Here, a versatile system is presented which addresses these challenges by employing centrifugal force to extrude polymer dope jet through an air gap, into a flowing precipitation bath. This voltage‐free approach ensures that nanofiber solidification occurs in liquid, minimizing surface tension instability that results in jet breakup and fiber defects. In addition, nanofibers of controlled size and morphology can be fabricated by tuning spinning parameters including air gap length, spinning speed, polymer concentration, and bath composition. To demonstrate the versatility of our platform, para‐aramid (e.g., Kevlar) and biopolymer (e.g., DNA, alginate) nanofibers are produced that cannot be readily produced using standard nanofiber production methods.
Subwavelength nanostructure arrays on surfaces improve their optical transmittance by reducing the reflection of light over a wide range of wavelengths and angles of incidence. A method to imprint a sub‐100 nm nanostructure array on a large surface (Ø 20 mm) made from thermoplastic materials is reported. Transmittance through the flat polymer is improved by ≈6.5%, reaching values of up to 97.5%, after imprinting. The optical properties of the nanostructured samples are highly reproducible. After eight repeated imprinting operations with the same stamp, the transmittance of the nanostructured surface is decreased by less than 0.2%. Moreover, the nanostructures can also be imprinted on curved polymethylmethacrylate surfaces, achieving a maximum transmittance of 97%. This method to prepare large‐scale antireflective nanostructures on flat and flexible curved polymer surfaces is of interest for the production of antireflective screens, optical devices, and biomedical devices such as contact lenses and intraocular lenses.
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