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.
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.
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.
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.
Colloidal assemblies of inorganic nanoparticles dispersed in liquid media hold particular promise for the creation of a unique class of functional materials with innovative applications. In the present report, “compound‐eye”‐like core–shell and Janus‐type silica and amino‐terminated 1,2‐polybutadiene (PB‐NH2) and polystyrene (PS) composite microspheres are successfully prepared by simply mixing an aqueous dispersion of silica particles into a tetrahydrofran (THF) solution of PB‐NH2, and PB‐NH2 and PS blends, followed by evaporation of the THF. This co‐precipitation process provides a new approach for producing organic–inorganic composite particles without the need for surface modification of the inorganic nanoparticles.
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.
Interfacial polymerization of dopamine and terephtaloyl chloride is performed on a porous crosslinked polyacrylonitrile support membrane. The resulting polymer layer has a smooth surface and is ultrathin (about 5 nm). The chemical nature of the interfacially polymerized layer is characterized by Fourier transform infrared spectroscopy and by X‐ray photoelectron spectroscopy. The thin‐film composite membrane is stable in aggressive solvents like dimethylformamide (DMF) and the membrane shows high solvent permeances combined with a molecular weight cut‐off below 800 g mol‐1. The remarkable stability in DMF, the ease of preparation as well as the extremely thin and smooth selective layer make this new type of bioinspired membrane attractive for solvent resistant nanofiltration.
Four bromine‐containing methacrylates 1 – 4 are synthesized from pentaerythritol tribromide and 2,2,2‐tribromoethanol and are characterized by 1H and 13C NMR spectroscopy. Their free radical polymerization is performed in dimethylformamide (DMF), using 2,2′‐azobis(2‐methylpropionitrile) as initiator. The photopolymerization behavior of monomers 1–4 is investigated using a differential scanning calorimeter. Homopolymerizations and copolymerizations with 2‐hydroxyethyl methacrylate are carried out. Both the presence of a carbamate group and of bromine atoms result in an increase of the polymerization rate. Dental resins are prepared by replacing a certain amount of 2‐(4‐cumyl‐phenoxy)ethyl methacrylate by monomers 3 and 4 in a model formulation. The incorporation of these methacrylates leads to a significant increase of the radiopacity. Resins based on monomer 4 exhibit improved mechanical properties.
Porous polymer materials prepared from biodegradable polymers have received considerable attention due to their potential as cell culture scaffolds for tissue engineering. Porous materials are generally sterilized by autoclaving prior to use as cell culture scaffolds to avoid unexpected biological infection. However, the melting point of biodegradable polymers is typically lower than the temperature used in autoclave sterilization. Here, the preparation of honeycomb films comprising a poly(L‐lactic acid) (PLLA) and poly(D‐lactic acid) (PDLA) stereo complex is described and their thermal stabilities are evaluated. The hierarchic photochemical patterning of PLLA/PDLA stereo complex honeycomb‐patterned films by UV‐O3 treatment is also demonstrated.
The fabrication of asymmetric polymer membranes via vapor phase deposition is demonstrated. In this solventless process, the dense layer is deposited first and then the porous layer is subsequently deposited onto the dense layer. A variety of functional polymer membranes can be produced by varying the precursor molecules. The functionality of the dense and porous layers can be independently tailored to be either hydrophobic or hydrophilic, resulting in membranes that are fully hydrophilic, fully hydrophobic, or asymmetric in both structure and chemical functionality. The thickness of both the porous and dense layers can be separately tuned by controlling the deposition time.
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.
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.
Superabsorbent hydrogel nanocomposites (SHN) with semi‐interpenetrating polymer network (semi‐IPN) are synthesized by the polymerization of acrylamide monomer in a polyethylene glycol aqueous solution in the presence of the octadecylamine (ODA)‐modified graphene oxide (GO‐ODA) nanosheets. The hydrogel composites are characterized by Fourier transform infrared spectroscopy, thermal gravity analysis, and scanning electron microscopy. The water absorbency of the resulting SHN in distilled water and saline solutions are measured. The results show that doping GO‐ODA nanosheets into hydrogel semi‐IPN would enhance both their salt resistance and water retention. Using a simple freezing‐dry method, porous SHN with macroscopically interconnected pores is prepared, which exhibits excellent separation ability for removal of trace water from oils. Based on their better water absorbency, salt resistance, and excellent oil/water separation ability, the resulting SHN has great potentials in a wide range of applications, for example, oil dehydration, absorption, and separation.
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.
Flexible polymers such as poly dimethyl siloxane (PDMS) can be patterned at the micro‐ and nanoscale by casting, for a variety of applications. This replication‐based fabrication process is relatively cheap and fast, yet injection molding offers an even faster and cheaper alternative to PDMS casting, provided thermoplastic polymers with similar mechanical properties can be used. In this paper, a thermoplastic polyurethane is evaluated for its patterning ability with an aim to forming the type of flexible structures used to measure and modulate the contractile forces of cells in tissue engineering experiments. The successful replication of grating structures is demonstrated with feature sizes as low as 100 nm and an analysis of certain processing conditions that facilitate and enhance the accuracy of this replication is presented. The results are benchmarked against an optical storage media grade polycarbonate.
The present work focuses on the influence of nucleation processes on the crystallization of bio‐based poly(ethylene 2,5‐furandicarboxylate) (PEF). Nuclei formation has been studied by means of fast scanning calorimetry (FSC) both when cooling from the melt (nonisothermal conditions) and when annealing at either low‐ or high‐temperatures (isothermal conditions). FSC results show that nucleation on cooling can be prevented by using fast rates allowing to keep the polymer in its amorphous state; whereas cooling at moderate rates results in sample nucleation with a subsequent increase of the crystallization rate. Isothermal pretreatment just above the PEF glass transition temperature (Tg) results in nuclei formation whose rate decreases when the nucleation temperature approaches PEF Tg. On the other hand, annealing below the PEF melting point allows determination of the sample self‐nucleation behavior which occurs in a very narrow temperature range, i.e., between 195 and 198 °C.
Three different dopants are used to fabricate electrospun dopants/polystyrene (dopants/PS) composite fibers from PS solution and PS sol. The relative humidity and the influence of the dopants on the morphologies, diameter, porous structures, and dopant distribution of electrospun PS fibers are investigated. Compared to those obtained from PS solution, electrospun dopants/PS composite fibers from PS sol with hollow‐porous and multichannel hollow‐porous structures present significant advantages due to the multi‐stage degree of interfacial structure and diversity of the internal environment. In comparison to coaxial electrospun PS fibers, the electrospun dopants/PS composite fibers from PS sol obtained in one step have an improved yield and a simplified technological process simultaneously, leading to significant competitiveness in fields such as catalysis, fluidics gas storage, and sensing.
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.
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.
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.
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