The introduction of nanodiamond particles (NDs) in silane‐crosslinked polyethylene is found to lead to a notable and systematic deformation of the polymer unit cell. X‐ray diffraction evidence of the existence of a modified crystalline structure in the bulk of the polymer due to the presence of NDs is reported here for the first time. The covalent bonding between NDs and the surrounding macromolecular chains may support that the excessive local stress field ultimately distorts the polymer conformation, yielding a new distorted but still crystalline interface. Supporting data from solid‐state NMR experiments confirm the existence of a modified crystalline interface of about 1–2 nm in all the nanocomposite materials.
A green polymer self‐etching strategy for fabricating superhydrophobic surfaces exhibiting low and high adhesion is proposed by using hot‐pressing and exfoliation on a pair of low density polyethylene (LDPE) films. It is demonstrated that the hot‐pressing temperature has significant influence on the surface morphology of LDPE. Effective hot‐pressing temperature for low‐adhesive superhydrophobicity ranges from 109 to 161 °C. Bird's‐nest like micro‐/nanostructures are observed in the unzipped LDPE surfaces compressed at 109 °C, which shows excellent water repellency. LDPE surface compressed at 108 °C demonstrates superhydrophobicity with high adhesion, i.e., a water droplet cannot roll off even when the surface is turned upside down. Furthermore, superhydrophobic vessels are processed and applied to transport water and microdroplets of water losslessly.
Hydrophobic and super‐hydrophobic materials have many important applications, but most of the artificially hydrophobic and super‐hydrophobic surfaces suffer from poor durability. Herein, a facile method is reported to fabricate robust hydrophobic and super‐hydrophobic polymer films through backfilling the silica colloidal crystal templates with the mixture of fluoropolymer, thermoset hydroxyl acrylate resins, and curing agent. After removal of the template, 3D ordered porous structures are obtained. The obtained polymer films have not only excellent hydrophobic or super‐hydrophobic properties but also good stability against temperatures, acids, and alkalis. Dual ordered porous structure can obviously enhance the hydrophobicity of polymer films compared to unitary one.
One major challenge of biomaterial engineering is to mimic the mechanical properties of anisotropic, multifunctional natural soft tissues. Existing solutions toward controlled anisotropy include the use of oriented reinforcing fillers, with complicated interface issues, or UV‐curing processing through patterned masks, that makes use of harmful photosensitive molecules. Here, a versatile process to manufacture biocompatible silicone elastomer membranes by light degradation of the platinum catalyst prior to thermal cross‐linking is presented. The spatial control of network density is demonstrated by experimental and theoretical characterizations of the mechanical responses of patterned cross‐linked membranes, with a view to mimic advanced implantable materials.
A new facile approach for the fabrication of polymer‐Ag honeycomb film is reported. A polymer‐Ag+ honeycomb thin film is obtained by casting a CHCl3 solution of a functional graft copolymer on aqueous silver nitrate solution, leading to metal complexation induced phase separation at the air/water interface. The film is reduced by UV irradiation to give a polymer‐Ag honeycomb film with regular morphology. Pyrolysis of the film gives a translucent Ag honeycomb film.
In the present study, the covalent bonding of electroconductive cross‐linked hydrogel networks with both electro‐properties and hydrogel characteristics to titanium surfaces via a UV‐initiated radical thiol‐ene click reaction is investigated. The electroconductive hydrogel layers are formed by the electropolymerization of pyrrole within the titanium implant‐supported gelatin methacrylate hydrogel. Characterization of the surface morphology of the layers reveals a unique rough macroporous structure. The hydrogel coating layer on the titanium surfaces possesses the desired characteristics of high electrochemical activity and high mechanical stability due to the effects of the chemical functionalization. Bone mesenchymal stem cells cultured on the hydrogel substrates exhibit high cell viability. This study is the first to demonstrate the potential of an electroconductive hydrogel as a surface coating on titanium implants for cell growth and provides a foundation for the development of new implantable bioelectronic devices.
Pollution control has become increasingly important in recent years. Heavy metal ions, proteins, and dyes are frequently found in wastewater because of their extensive industrial applications. In this study, pH, temperature, and magnetic triple‐responsive poly(N‐isopropylacrylamide‐co‐methacrylic acid) porous microspheres doped with magnetite nanoparticles as a new type of smart adsorbents are used to remove the aforementioned pollutants. The pH‐ and temperature‐responsiveness of these microspheres realizes tunable adsorption toward Cu(II). Simultaneously, the microspheres exhibit good adsorption capability to lysozyme and basic fuchsine. Microsphere‐adsorbing pollutants are easlily separated from wastewater by applying an external magnetic field to reuse the microspheres.
Most insect eyes use microvillar photoreceptors, where the visual pigment rhodopsin is aligned within tubular microvilli, endowing the insects with amazing navigation ability through detecting the polarization of illuminating light in the sky. Herein, polydiacetylene‐polystyrene (PDA‐PS) hybrid microfibers are fabricated by electrospinning method and it is demonstrated that PDA‐PS hybrid microfibers exhibit interesting polarized waveguiding properties, which is found to be dependent on the ordered alignment of PDA chains, but not on the propagating distance or the wavelength of the excitation light. Moreover, three PDA‐PS microfibers with different polarized waveguiding behavior can be assembled together as polarization sensitive photoreceptors to mimic the natural rhabdome arrays in insect eyes, since the physical dimensions, structure, and function of single PDA‐PS microfiber are comparable to that of natural rhabdomere.
We herein report on an iontronic device to drive and control Aβ1‐40 and Aβ1‐42 fibril formation. This system allows kinetic control of Aβ aggregation by regulation of H+ flows. The formed aggregates show both nanometer‐sized fibril structure and microscopic growth, thus mimicking senile plaques, at the H+‐outlet. Mechanistically we observed initial accumulation of Aβ1‐40 likely driven by electrophoretic migration which preceded nucleation of amyloid structures in the accumulated peptide cluster.
Dopamine is a molecule that facilitates biomineralization, and it is used to prepare electropolymerization‐induced polydopamine (PDA). For the first time, dopamine is used for template‐free electrochemical polymerization to form biocompatible polypyrrole (PPy) nanofiber coatings on bone implants. Dopamine monomers are electropolymerized to PDA chains affixed to biomedical titanium after the nanomicelles are tuned to self‐assemble by triggering the potential, resulting in nanofiber formation. Dopamine serves as a dopant to induce the formation of conductive PPy nanofibers and as a promoter to accelerate biomineralization, cell proliferation, and adhesion.
A new stereo pentablock copolymer consisting of poly(l ‐lactide) (PLLA: A), poly‐d ‐lactide (PDLA: B), and poly(butylene succinate) (PBS: C) is synthesized by two‐step ring‐opening polymerization of d ‐ and l ‐lactides in the presence of bis‐hydroxyl‐terminated PBS prepolymer that has been prepared by the ordinary polycondensation. The pentablock copolymers (PLLA‐PDLA‐PBS‐PDLA‐PLLA) as well as the triblock copolymers (PLLA‐PBS‐PLLA) obtained as the intermediates show different properties depending on the polymer compositions. In the pentablock copolymers, the direct connection of the PLLA and PDLA blocks allows easy formation of the stereocomplex crystals, while the introduction of the semicrystalline PBS block is effective not only for changing the crystallization kinetics but also for imparting an elastomeric property.
Light triggered soft actuator in aqueous media has applications in operating underwater objects, creating liquid flow, and adjusting reaction velocity, etc. Here, composites prepared from commercial materials, poly[ethylene‐ran‐(vinyl acetate)] (EVA) and aniline black (AB), are reported as one cost efficient material for preparing such actuator, where EVA and AB work respectively as shape‐memory polymer matrix and near‐infrared light triggered photothermal filler. Upon irradiation, the temperature of the composites increases greatly with light power density and AB content. Light‐induced shape‐memory effect (SME) with recovery ratio >98%, temperature‐memory effect (TME), and reversible bidirectional shape‐memory effect (rbSME) of the prepared composites in air are realized. Higher light power density is required to trigger the shape recovery in aqueous media, while good SME, TME, and rbSME are also achieved. Releasing device and gripper are used to indicate the feasibility of the composites as light triggered soft underwater actuators.
This paper describes a mixture of fatty acids that is available for temperature‐controlled release of drugs. The mixture consists of two fatty acids with different melting points. At a specific composition, the mixture represents a single melting point of 38–40 °C which is slightly above the normal human body temperature. To demonstrate its use in the temperature‐regulated release, this study fabricates fatty acid‐incorporated polymer fibers containing dye‐loaded polymer particles in their core. Below the melting point of the mixture, it will be in a solid state to restrict the passing of dye loaded in the core whereas the dye can be released instantly through the generated pores at a temperature slightly higher than the melting point. The release profiles of the dye can be further manipulated by varying the amount of the mixture contained in the fibers and the composition of the mixture.
A self‐healing polysaccharide hydrogel based on dynamic covalent enamine bonds has been prepared with a facile, cost‐effective, and eco‐friendly way. The polysaccharide hydrogel is obtained by mixing cellulose acetoacetate (CAA) aqueous solution with chitosan aqueous solution under room temperature. CAA is synthesized by reaction of cellulose with tert‐butyl acetoacetate (t‐BAA) in ionic liquid 1‐allyl‐3‐methylimidazolium chloride (AMIMCl). The structure and properties of CAA are characterized by FT‐IR, NMR, and solubility measurements. The results demonstrate that CAA possesses water solubility with a degree of substitution (DS) about 0.58–1.11. The hydrogel shows an excellent self‐healing behavior without other external stimuli and good stability under physiological conditions. Furthermore, the polysaccharide hydrogel exhibits pH responsive properties.
Silicone materials are widely used in many fields such as electrical or food industries and their consumption is constantly growing. They are generally cured by vulcanization reaction for long time at high temperatures which requires high energy consumption. The possibility to achieve the polymerization of silicone rubbers by UV‐activation promotes the reduction of both time and temperature leading to an impressive energy saving. Indeed, this process is more than 30 times faster than the thermal one. Moreover, the properties of the two resulting materials are comparable, indicating that the low time of UV‐activated hydrosilation reaction is suitable for the formation of crosslinked silicone polymers.
A conjugated polymer, poly(9,9‐bis(6‐bromohexyl)‐9H‐fluorene‐alt‐1,4‐phenylene), is synthesized, converted to nanoparticles via a nanoprecipitation process, and utilized to fabricate thin films including conjugated polymer nanoparticles. The nanoparticles with surface bromides can be conjugated with an amine‐functionalized dendrimer via a nucleophilic coupling reaction. Thus, when microliter solutions of the particulates are dragged at a constant velocity on substrates alternately in a layer‐by‐layer manner, thin films composed of the nanoparticles and dendrimers can be successfully built up on the substrates. Our results suggest a methodology to control the deposition of thin films bearing conjugated polymer nanoparticles while minimizing processing time and decreasing material consumption.
Silicone‐based elastomers are promising materials for future dielectric elastomer actuators. To ensure optimum performance and the long‐term reliability of the actuators, it is essential to gain a fundamental understanding of the correlation between the elastomer's network structure and the mechanical and electrical responses of the material. For this purpose, mechanical and electrical tests are performed on a series of silicone elastomer films with different crosslinking densities, which are prepared by changing the stoichiometric imbalance of the network. It is determined that higher cross‐linking density leads to a higher elastic modulus and a longer fatigue lifetime, whereas reduced permittivity is observed because of lower chain mobility. Dielectric breakdown strength is also observed to increase in line with increasing cross‐linking density, and the variations in relation to the measured elastic modulus and permittivity agree well with the Stark–Garton model based on electromechanical instability.
Nanofiber‐based hydrocolloid scaffold is prepared by colloid electrospinning of thermoplastic polyurethane (TPU)/sodium carboxymethyl cellulose (S.CMC) in tetrahydrofuran (THF)/dimethylformamide (DMF). The most suitable process of electrospinning for successful formation of fibers is investigated by controlling the concentration of polymeric solution and co‐solvent ratio. In order to accomplish high wettability, the amount of colloid (S.CMC) and the co‐solvent ratio (THF/DMF), which affects the morphology of fibers, are adjusted. Finally, the open wound healing effect is confirmed using nanofiber‐hydrocolloid from in vivo animal studies. A detailed study of the wound healing process is also demonstrated for the first time.
In this work, anisotropic conductive film (ACF) is fabricated by shear‐flow induced assembly. It is found that an appropriate content of carbonaceous filler is needed for forming well‐ordered parallel vorticity‐aligned stripes and the content depends on the category of the filler. Interestingly, the lowest aspect ratio carbon black (CB) with lowest electrical conductivity is the best candidate for fabricating ACF. The film with CB stripes shows excellent conductive anisotropy: the electrical resistivity in the direction parallel to the CB stripes is almost eight orders of magnitude lower than that in the perpendicular direction. The formation mechanism of the vorticity‐aligned stripe is also investigated by the rheological measurement and the study of morphological evolution. It is found that the coalescence of dispersed phase or aggregates dominates the formation and growth of the stripe and negative value of the first normal stress difference drives the stripe to align along the vorticity direction.
This study describes novel and simple conditions for the fabrication of collagen microfibers with specific physical and mechanical properties, which can then be potentially applied as cell‐based matrices. The microfibers are fabricated from collagen hydrogels, using various concentrations of ethanol, in ethanol–water solvents. At higher ethanol concentration, fibers exhibited increased uniformity of surface morphology, decreased diameter, and increased tensile strength. The morphology of cells on microfibers varies due to the surface morphology of microfibers but the microfibers fabricated under all conditions investigated show similar number of attached cells on the surface of fibers, and cells sustain their viability for 90 h.
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