The physical and mechanical properties of novel bio-based polymer blends of polylactic acid (PLA), poly(butylene succinate) (PBS), and poly (butylene adipate-co-terephthalate) (PBAT) with various ...added amounts of nanohydroxyapatite (nHA) were investigated in this study. The formulations of PLA/PBS/PBAT/nHA blends were divided into two series, A and B, containing 70 or 80 wt% PLA, respectively. Samples of four specimens per series were prepared using a twin-screw extruder, and different amounts of nHA were added to meet the regeneration needs of bone graft materials. FTIR and XRD analyses were employed to identify the presence of each polymer and nHA in the various blends. The crystallization behavior of these blends was examined using DSC. Tensile and impact strength tests were performed on all samples to screen feasible formulations of polymer blends for bone graft material applications. Surface morphology analyses were conducted using SEM, and the dispersion of nHA particles in the blends was further tested using TEM. The added nHA also served as a nucleating agent aimed at improving the crystallinity and mechanical properties of the blends. Through the above analyses, the physical and mechanical properties of the polymer blends are reported and the most promising bone graft material formulations are suggested. All blends were tested for thermal degradation analysis using TGA and thermal stability was confirmed. The water absorption experiments carried out in this study showed that the addition of nHA could improve the hydrophilicity of the blends.
Cell therapy is used to treat various diseases and to repair injuries. Cell delivery is a crucial process that delivers cells to target sites. Cells must be precisely delivered to a target site and ...the cells that are delivered must be localized to the target site to repair damaged tissue. For stem cell therapy, the most convenient method of cell delivery involves directly injecting cells into damaged tissue. Other strategies use carriers to transplant stem cells into damaged tissue. These are termed, stem cell delivery systems (SCDSs). Micro-needle arrays are minimally invasive transdermal delivery systems. The devices can pass through the stratum corneum barrier and deliver macromolecules into the skin. They can also access the microcirculation system in the skin. This study fabricates PMMA micro-needle using a two-stage micro-molding method. Cells are seeded on the micro-needle arrays and then transferred into the target tissue. Collagen hydrogel is used as a model biomimetic tissue. Cells are efficiently delivered to regions of interest, collagen hydrogel, by using this system. The delivery rate is about 83.2%. This demonstrates that micro-needle arrays allow very efficient delivery of cells.
Polymer properties along with recycling processes remain a constant challenge for post-recycled polymers. In this study, the development of recycling feasibility, monomers reactivity, and the ...chemical-recycled polymer properties from polycarbonate (PC) waste were demonstrated. Through selective aminolysis under mild conditions, the reduced molecular-weight products (or monomer mixtures) with newly incorporated flexible-ether linkages as building blocks were realized. By using the commodity monomers such as isocyanate reagents, monomer mixtures were readily to be re-connected into polyurethanes in one-pot process without prior purification of the recycled monomer mixtures. Due to the presence of urethane groups, the enhanced reactivity of the terminal phenolic hydroxyl groups of the monomer mixtures toward isocyanate groups would afford high molecular weights over ~80,000 g/mol for thermoplastic polyurethanes (TPUs). Moreover, by taking advantage of low melting point polyether-type polyols along with optimizing processing conditions, the TPUs exhibited a unique phase separation morphology with domain sizes ranging from ~10 nm to ~25 nm as investigated by using small angle X-ray scattering (SAXS) measurements. This work demonstrate that the PC waste was fully transformed into TPUs which exhibited improved elastomeric properties.
This work demonstrates that the PC waste was depolymerized to monomer mixtures and subsequently transformed into recyclable thermoplastic polyurethanes exhibiting robust elastomeric properties. Display omitted
•Monomer mixtures derived from the aminolysis of polycarbonates.•Thermoplastic polyurethane elastomers prepared from recycled monomer mixtures.•Diphenolic carbamates as hard segments for TPUs.•Ｍicrophase separation and semi-crystallinity morphologies.•Tensile properties comparable with those of TPUs prepared from pristine raw materials.
Passive daytime radiative cooling (PDRC), as a strategy to dissipate heat through an atmospheric transparency window (ATW) to outer space without any extra energy consumption, has been recently ...considered as a novel approach for global net-zero emissions. However, limited to expensive manufacturing, poor thermal/chemical stability, or insufficient weather-resistance, the development of a PDRC building material for long-term outdoor usages still remains a challenge. Here, a scalable superhydrophobic silica metafibers (sh-SMF) was fabricated via an electrospinning process combined with the fluorosilane-modification on fiber surface. The optically engineered sh-SMF could attain an extremely high average reflectivity (∼97 %) with near-zero absorption in the solar spectral region, due to the multiple backscattering at the fiber/air interfaces. In addition, the sh-SMF possessed a high average emissivity (∼90 %) in ATW, originated from the strong phonon resonances of the abundant Si-O bonds. Thus, the optimal sh-SMF realized a sub-ambient cooling performance of 6 °C (4 °C in nighttime) and the maximum cooling power of 112 W/m2 (87 W/m2 in nighttime) under a solar irradiance of ∼790 W/m2. Besides, the temperature decline for the sh-SMF-covered building and vehicle models could also achieve 12.7 °C and 17 °C under sunlight, respectively. Noteworthily, the ceramic sh-SMF could withstand high temperatures over 1200 °C, which might effectively prolong the time for resident to evacuate from buildings in fireground situation. Moreover, the superhydrophobic surface (contact angle=155°) of sh-SMF demonstrated attractive self-cleaning and anti-mildew properties. Furthermore, the excellent weather resistance against acid rain and ultraviolet exposure endowed the sh-SMF with long-term cooling performance. Finally, the sh-SMF with above mentioned properties opens a path for future energy-efficient and sustainable architectural applications.
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•Superhydrophobic silica metafibers (sh-SMFs), fabricated through electrospinning, serving as a scalable, flexible, and flame- and weather-resistant ceramic PDRC emitter.•The optimal sh-SMFs operated with a near-zero value of Psun (<3 W/m2), and a high value of Pcooling (112 W/m2) during the daytime, resulting from high solar reflectivity (97 %) and thermal emissivity (90 %).•Maximum temperature decreases of sh-SMF–covered building and vehicle models of 12.7 and 17 °C, respectively, under sunlight.•The sh-SMFs could withstand high temperatures (>1200 °C), making them especially suitable as a building material that could effectively prolong the time available for residents to evacuate buildings in the event of fire.•The sh-SMFs display excellent self-cleaning, anti-mildew, and anti-acid abilities, combined with great UV-resistance, resulting in great weather-resistance for long-term outdoor applications.
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•Highly porous hydrogels based on mixtures of PEG and poloxamer can be fabricated via solvent-induced phase separation.•The porosity from 20% to 75% and open/closed pore structure can ...be fine-tuned by varying composition and solvent type.•The subcutaneous implantation results suggest good cytocompatibility of the material implant.•Highly biocompatible and superporous hydrogel scaffolds show potential to be used as corneal periphery in the future.
Biocompatible and highly porous network hydrogel scaffolds were fabricated for the development of artificial cornea (AC) periphery/skirt that could be used to enhance the long-term retention of the implants. In this study, a series of hydrogel scaffolds for this application was fabricated from the photo-polymerization of a mixture of poly(ethylene glycol) (PEG)- and poloxamer (P407)-based macromer solutions in dichloromethane in which solvent-induced phase separation (SIPS) arose to form scaffolds with macroporous structure and high water content. The overall porosity ranging from 20% to 75% and open/closed pore structure of the hydrogel scaffolds could be finely tuned by varying the ratio of P407/PEG in the macromer solution and solvent type. The total porosity and open-cell structure of the macropores in the synthesized hydrogel scaffolds affected the swelling behavior, dynamic properties such as the storage moduli of the hydrogels as well as their degradation rates. Based on the subcutaneous implantation in rats, superporous hydrogel scaffolds induced the formation of thinner fibrous capsules around the implants and showed less inflammatory reaction, suggesting that the hydrogel scaffolds made from SIPS exhibited good cytocompatibility. The combined results of swelling ratio, porosity, physical strength and subcutaneous implant tests indicated that the superporous hydrogels with porosity >50% showed potentials to be used for cornea periphery application.
The introduction of additives with specific functional groups is an important approach to extend the operational lifetime of perovskite solar cells (PSCs). Herein, the effect of the additives of ...benzoic acid (0F‐B), 4‐fluorobenzoic acid (1F‐B), and 2,3,4,5,6‐pentafluorobenzoic acid (5F‐B) on the performance and stability of MAPbI3‐based PSCs is systematically investigated. These additives can both chelate onto lead ions and form hydrogen bond with methyl ammonium ions. These combined interactions result in an increased activation energy for nucleation of perovskite crystals, thereby, increasing crystal size, reducing defect formation, improving electronic properties, as well as reducing ion migration. As a result, PSCs added with 5F‐B achieve the highest power conversion efficiency (PCE) of 20.50% with a narrow distribution compared to those PSC devices added with 1F‐B (19.25 %), 0F‐B (18.80 %), and pristine devices (18.53 %). Notably, 5F‐B‐added PSCs retain 80% of their initial PCE after ≈100‐day humidity test (at 25 °C and 50% relative humidity), 30‐day thermal stability test (at 85 °C in nitrogen environment), and 12‐day light illumination test (under continuous simulated solar radiation).
The additives of benzoic acid and its fluorinated derivatives synergistically passivate the perovskite layer, resulting in improved crystallinity and surface morphology, leading to an increased efficiency. More importantly, this approach enhances the long‐term stability of the architected devices, rendering them more suitable for future commercial applications.
•An ultrasound-responsive hydrogel based on N-isopropylacrylamide is proposed.•Ultrasound induces release of bovine serum albumin and dextran from the hydrogel.•Ultrasound increases the release ...through thermal and non-thermal effects.•A positive correlation between the ultrasound intensity and release amount exists.•Difference of release between presence and absence of ultrasound can be adjusted.
Episodic release of bioactive compounds plays an important role in biological systems. “On-demand” release systems which based on polymeric materials and activated by external stimuli may provide the necessary functionality. Here we describe an ultrasound-responsive hydrogel based on N-isopropylacrylamide (NIPAM) and N,N′-methylenebisacrylamide (MBAm), which is suitable for triggered release of two large molecules: bovine serum albumin (BSA, 66kDa) and dextran (3–5kDa). It is shown that the release amount of these two large molecules increased with increasing hydrogel temperature, and the application of ultrasound further increased the release. By simply adjusting the contents of NIPAM and MBAm, the difference of BSA release between the presence and absence of ultrasound could be adjusted from 2.7 to 84 folds. There was also a positive correlation between the ultrasound intensity and release amount. These properties made the NIPAM-based hydrogel a tunable platform for focal drug delivery.
In this study, we developed a novel in situ hydrothermal method to fabricate self-assembled P3HT/TiO2 hybrid nanowires, wherein a facile one-step synthetic strategy was utilized to co-organize P3HT ...molecules and titanium precursors into highly elongated hybrid nanowires, followed by a hydrothermal process in an autoclave to in situ transform the titanium precursors into crystalline TiO2 nanoparticles on the P3HT nanofibrils. P3HT nanofibrils were utilized as a structure-directing motif to achieve a favorable dispersion of electron acceptor (A) TiO2 nanocrystals of 10-15 nm in diameter embossed along the nanofibrils, as well as an efficient electron donor (D) for the nanohybrid. In particular, the crystallization temperature of anatase-phase TiO2 nanoparticles with high crystallinity obtained via the hydrothermal method was significantly reduced to 130 degree C in an elevated pressure of similar to 7 bars as compared to the conventional calcination temperature of 450 degree C at ambient pressure for TiO2 nanocrystal synthesis, therefore, allowing the synergistic one-step fabrication of both highly crystalline TiO2 nanoparticles embossed on highly crystalline long-range ordered P3HT nanofibrils. As a consequence of the structural development, this P3HT/TiO2 embossed nanohybrid could afford significant improvements in its D/A interfacial contact area for effective charge separation without the need for capping ligands typically used in ex situ D/A blend systems, as well as an efficient pathway for charge transport, leading to enhanced optoelectronic properties and device performance. The highest conversion efficiency of 0.14% was presented by the P3HT/TiO2 embossed hybrid device, which was a remarkable improvement as compared to only 0.03% from an ex situ P3HT/TiO2 hybrid device. This novel in situ approach shows a feasible way to fabricate organic/inorganic nanohybrid materials of conjugated copolymers with different inorganic nanoparticles for the applications of future optoelectronic devices.
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The impact of the β-cyclodextrin (β-CD) on the graphene oxide (GO) was considerably altered the activity of electrochemical sensors. Hence, the present study, we scrutinized the ...electrocatalytic determination of nitrobenzene (NB) by changing the different loading level of β-CD on GO modified electrodes. The composites were prepared by the simple ultrasonication method and characterized by UV–Visible spectroscopy, infrared spectroscopy and scanning electron microscope. Interestingly, the synergistic electrocatalytic activity was appeared for the 1.2mg β-CD loaded GO (β-CD1.2mg/GO) to the determination of NB whereas bare SPCE, GO and other β-CD loaded GO/SPCE exhibited the lower electrocatalytic activity. The β-CD1.2mg/GO composite modified SPCE was furnished the linear concentration range from 0.5–1000μM and showed the lowest detection limit of 0.184μM. Moreover, it exhibited high sensitivity, acceptable reproducibility and good stability. Besides, the proposed sensor was demonstrated its practicability in real water samples.
Driven by molecular affinity and balance in the crystallization kinetics, the ability to co-crystallize dissimilar yet self-crystallizable blocks of a block copolymer (BCP) into a uniform domain may ...strongly affect its phase diagram. In this study, we synthesize a new series of crystalline and monodisperse all-π-conjugated poly(2,5-dihexyloxy-
p
-phenylene)-
b
-poly(3-(2-ethylhexyl)thiophene) (PPP-P3EHT) BCPs and investigate this multi-crystallization effect. Despite vastly different side-chain and main-chain structures, PPP and P3EHT blocks are able to co-crystallize into a single uniform domain comprising PPP and P3EHT main-chains with mutually interdigitated side-chains spaced in-between. With increasing P3EHT fraction, PPP-P3EHTs undergo sequential phase transitions and form hierarchical superstructures including predominately PPP nanofibrils, co-crystalline nanofibrils, a bilayer co-crystalline/pure P3EHT lamellar structure, a microphase-separated bilayer PPP-P3EHT lamellar structure, and finally P3EHT nanofibrils. In particular, the presence of the new co-crystalline lamellar structure is the manifestation of the interaction balance between self-crystallization and co-crystallization of the dissimilar polymers on the resulting nanostructure of the BCP. The current study demonstrates the co-crystallization nature of all-conjugated BCPs with different main-chain moieties and may provide new guidelines for the organization of π-conjugated BCPs for future optoelectronic applications.
Driven by molecular affinity and balance in the crystallization kinetics, the ability to co-crystallize dissimilar yet self-crystallizable blocks of a block copolymer (BCP) into a uniform domain may strongly affect its phase diagram.
