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.
The flame retardancy and mechanical properties of polyamide‐6 (PA6)/aluminum diethylphosphinate (AlPi) composite are greatly improved by the addition of novelly synthesized phosphorus flame retardant‐based diepoxide (DEP) during extrusion. The PA6/AlPi/DEP composite passes V‐0 rating of UL94 test with limiting oxygen index (LOI) of 32.6% at 13 wt% AlPi and 1 wt% DEP, as revealed by the results of flammability. The synergistic flame retardation mechanism offered by the two additives (AlPi and DEP) is studied in terms of in‐depth characterization of the charred residue and evolved gas. The deteriorated mechanical strength of PA6 due to existence of AlPi is compensated by the simultaneous chain extension effect of DEP. Accordingly, the flexural and impact strengths of PA6/AlPi/DEP composite are even superior to those of neat PA6.
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 gas‐permeable cellulose template for microimprint lithography has been synthesized and characterized for the reduction of template damage and gas trapping caused by solvents and oxygen generated from cross‐linked materials. The 5 μm line‐pattern failure of the microimprinted UV cross‐linked liquid materials with 4.7 wt% acetone as a volatile solvent is solved by using the gas‐permeable cellulose template because of its increased oxygen permeability. The gas‐permeable cellulose template also allows the use of volatile solvents with high coating property and solubility into the microimprinted materials instead of the compounds and plastic resins conventionally used in mold injection.
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.
Using a technique called solution blow spinning, polyurethane–carbon nanotube‐based composite nanofibers are fabricated. These composite nanofibers exhibit uniform diameter, even with increasing polyurethane density, with the use of a dual‐solvent mixture during spinning. It is possible to produce the fibers at a high production rate even after the addition of a large amount of carbon nanotubes with a uniform size distribution of 300–400 nm. In addition, for composites with 3 wt% carbon nanotubes, the tensile strength, elongation, and elastic strain energy increase to 102, 166, and 167%, respectively, compared to pure PU nanofibers. The thermal stability improves as well. The prepared composite nanofibers could potentially be used as an inter‐reinforcing agent in carbon‐fiber‐reinforced plastics and as a buffer, and in the biomedical field.
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.
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.
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.
Preparation of novel nanocomposite hydrogels opens up new avenues to next generation of biocompatible materials to be used in bioengineering and drug delivery. Toward this goal, chitosan nanocomposite hydrogels using click chemistry inspired cross‐linking are prepared. To enable this, Diels–Alder reaction of furan‐containing chitosan and maleimide‐coated gold nanoparticles is employed. The viscoelastic properties of the obtained nanocomposites as well as the effect of the nanoparticles as cross‐linkers are studied, indicating that they play significant role in hydrogel formation and stability. Nanoparticle‐enriched hydrogels are also found to demonstrate pH‐sensitivity therefore showing their potential for future biosensing applications.
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.
The previously introduced process for enzyme‐mediated in situ synthesis and deposition of eumelanin is investigated with covalent immobilization of the tyrosinase. It results in a monolayer structure of non‐coalesced melanin particles, with a film thickness of 5–8 nm. The reaction is self‐terminating due to overlay of the enzymes with particles. The melanin particles are rodlike with lengths down to 6 nm. Isolated melanin structures of such small size have not been observed before and might be a kind of protoparticle in the supramolecular buildup of melanin oligomers. Utilization of melanin particles with such small size can enable nanotechnological applications in the areas of bioelectronics and biosensors.
In this study, polyamide 6/polystyrene in situ microfibrillar blends are prepared via anionic polymerization of ε‐caprolactam in a twin screw extruder. Scanning electron microscope analysis reveals that microfibrillated PA6 dispersed phase, which is continuous and preferentially oriented parallel to the extrusion direction, is in situ formed within polystyrene (PS) matrix during reactive extrusion at the content PS equal to 30 and 40 wt%. Mechanical properties analysis shows that the yield strength and elongation at break of PA6/PS (70/30 and 60/40) microfibrillar blends are remarkably increased with respect to those of pure PS. Also, the in situ fibrillation mechanisms are investigated by the analysis of morphological evolution. This work demonstrates a facile and efficient route to fabricate the microfibrillar blends with relatively high contents of polymer microfibrils.
We report a novel method for oil/water separation using stainless steel meshes functionalized with amphiphilic copolymer, poly(methacrylic acid‐co‐ethylhexylmethacrylate) (PMAA‐co‐EHMA), brushes. Because the PMAA‐co‐EHMA brush‐covered surfaces show a large contact angle hysteresis at the oil/water contact line, the meshes can be programmed to act as either water‐selective or oil‐selective filters simply by pre‐wetting the mesh with one of these liquids. These programmable meshes can separate oil/water mixtures to high filtrate purities (more than 99 % mol/mol) in both oil‐selective and water‐selective modes.
Poly(ethylene glycol) (PEG)‐based hydrogels have attracted increasing attention in recent years due to their good biocompatibility and low cost. However, the PEG‐based hydrogels prepared by traditional methods exhibit a poor machinability due to their disordered network structure. Herein, the preparation of well‐defined PEG‐based hydrogel via a facile thermally induced copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction is demonstrated. To accomplish this, thermochemically reduced Cu(I) catalyst is adopted to trigger “click” cross‐linking, resulting in a well‐defined PEG network. The as‐synthesized PEG‐based hydrogel exhibits good mechanical performance with a tensile strength of 2.51 MPa, which is higher than the traditional PEG‐based hydrogels prepared from CuSO4/NaSac‐mediated or CuBr/ligand‐catalyzed CuAAC. Moreover, in vitro cytotoxicity and in vivo porcine subcutaneous implantation tests demonstrate that the as‐synthesized PEG‐based hydrogel has a good biocompatibility and low toxicity, making it a promising candidate for the applications in biomedical devices and tissue engineering.
Suitable membranes for blood‐contacting medical applications need to be resistant in confrontation with blood proteins and cells, while possessing high blood compatibility and permeability at the same time. Herein, an overview of the recent advances and strategies that have been used to enhance the hemocompatibility of polymeric membranes is provided. The review focuses on two modification strategies: (i) physical modifications and (ii) chemical modifications. It also highlights the current progress in the design of hemocompatible‐functionalized membranes for biomedical applications. Subsequently, the commonly applied biocompatibility tests are also discussed and finally the future perspectives of the application of polymeric membranes in the biomedical field are presented.
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.
The mechanical properties and microstructure of injection molded isotactic polypropylene parts with high orientation before and after annealing are analyzed. The mechanical properties of the annealed samples are improved effectively. Through thorough analysis of various structural characterizations, a microstructural model based on the fact that the total length of long period kept constant to analyze the variation of mechanical properties is proposed. It is suggested that the increase of overall crystallinity, the recombination of crystalline phase, and the increase of amorphous phase, respectively, are beneficial for the improvements of the strength, stiffness, and toughness of annealed samples.
Mechanically robust and self‐healing rubbers are highly desired to satisfy the increasing demand of high‐performance smart tires and related materials. Herein, a self‐healing rubber nanocomposite with enhanced mechanical and self‐healing performance based on Diels–Alder chemistry has been investigated. The furfuryl grafted styrene‐butadiene rubber and furfuryl terminated MWCNT (MWCNT‐FA) are reacted with bifunctional maleimide to form a covalently bonded and reversibly cross‐linked rubber composite. Obvious reinforcing effect is obtained at high cross‐linking density. Over 200–300% increase in the Young's modulus and toughness can be achieved in the rubber nanocomposites with 5 wt% MWCNT‐FA. Meanwhile, the healing efficiency increased with MWCNT‐FA content. MWCNT‐FA plays dual roles of effective reinforcer and a kind of healant.
This paper reports on how the blend ratio and morphology influence the mechanical, thermal, thermomechanical, and rheological properties of poly(propylene) (PP)/low density polyethylene (LDPE) blends. The blend morphology is composed of the major matrix phase and the minor phase, with subinclusions of the major matrix existing within the minor phase. Blends containing low amounts (<20 wt%) of either phase exhibit partial miscibility but the phases are immiscible at higher contents. Partial miscibility of the blends is revealed by scanning electron microscopy studies showing fibril‐like structures and confirmed by rheology. The tensile modulus of the blends decreases with increasing amounts of LDPE, but low LDPE contents exhibit positive deviation from the mixing rule of mixture due to partial compatibility. The crystallinity of PP is affected less than that of LDPE in the blends. Thermomechanical and rheological properties of neat polymers are significantly influenced by blending. The blend ratio and morphology influence impact strength and elongation at break, and the result demonstrates that the 80/20 PP/LDPE blend offers a balance among the mechanical and material properties that are essential for flexible packaging applications.
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