Well‐defined block copolymers consisting of hyperbranched polyamide (HBPA) and polystyrene (PSt) are synthesized, and their self‐assembled structures in solutions are investigated. Atom transfer ...radical polymerization (ATRP) of styrene initiated from an HBPA macroinitiator, prepared by the chain‐growth condensation polymerization of an AB2 monomer, followed by introduction of an ATRP initiator unit at the focal point, gives the desired block copolymers, PSt‐b‐HBPAs, with well‐defined molecular weight and narrow molecular weight distribution. The block copolymer (PSt/HBPA = 84/16) undergoes self‐assembly in toluene to form spherical micelles (≈10–20 nm), but upon addition of methanol to the toluene solution (toluene/methanol = 0.97/0.03), the morphology changes to vesicles. Further addition of methanol (toluene/methanol = 0.90/0.10) leads to an increase in vesicle size (200–300 nm) and the morphology further transforms from vesicles to large aggregates (>100 nm) at toluene/methanol = 0.80/0.20. In the case of PSt‐b‐HBPA with shorter PSt segments (PSt/HBPA = 76/24 and 60/40), spherical micelles are formed in toluene, but the micelle morphology remains unchanged when 10 wt% methanol is added, though large aggregates (>100 nm) are still formed in toluene/methanol = 0.80/0.20. Interestingly, the morphological transformations of linear/hyperbranched block copolymers are different from those of their double linear block copolymer counterparts.
Well‐defined diblock copolymer consisting of hyperbranched polyamide (HBPA) and polystyrene (PSt) is synthesized by atom transfer radical polymerization of styrene with HBPA macroinitiator. Self‐assembly of PSt‐b‐HBPA in toluene formed micelles, which are converted to vesicles upon addition of a small amout of methanol to the toluene solution. The morphology is further changed to large aggregates upon addition of 20% methanol.
The blindness caused by cornea diseases has exacerbated many patients all over the world. The disadvantages of using donor corneas may cause challenges to recovering eye sight. Developing artificial ...corneas with biocompatibility may provide another option to recover blindness. The techniques of making individual artificial corneas that fit the biometric parameters for each person can be used to help these patients effectively. In this study, artificial corneas with different shapes (spherical, aspherical, and biconic shapes) are designed and they could be made by two different hydrogel polymers that form an interpenetrating polymer network for their excellent mechanical strength. Two designed cases for the artificial corneas are considered in the simulations: to optimize the artificial cornea for patients who still wear glasses and to assume that the patient does not wear glasses after transplanting with the optimized artificial cornea. The results show that the artificial corneas can efficiently decrease the imaging blur. Increasing asphericity of the current designed artificial corneas can be helpful for the imaging corrections. The differences in the optical performance of the optimized artificial corneas by using different materials are small. It is found that the optimized artificial cornea can reduce the high order aberrations for the second case.
Although cold-pressed sesame oil (CPSO) possesses high nutritional value, its application in the food industry is limited due to its poor oxidative stability. The aim of this study was to enhance the ...oxidative stability of CPSO by complex coacervation microcapsule technology with gelatin and gum Arabic as wall materials. The characterization of CPSO microcapsules were evaluated by a particle image analyzer, a laser particle size distribution analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The encapsulation efficiency (EE) reached 90.25%. The average particle size of the microcapsules was approximately 117.1 μm and many oil droplets were encapsulated by complex coacervation to form a multinuclear spherical microcapsule. The FTIR study confirmed that the process of complex coacervation was formed between gelatin and gum Arabic by electrostatic interactions. The TGA study suggested that the microcapsules had good heat resistance. The fatty acid composition, the content of sesamin, sesamolin and vitamin E in CPSO were determined before and after microencapsulation. It showed that the microencapsulation process had almost no effect on the fatty acid composition, sesamin and sesamolin, only Vitamin E was slightly lost during the microencapsulation process. The accelerated storage test showed that microencapsulation significantly increased the oxidative stability of CPSO.
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.
Surface-enhanced Raman scattering (SERS) technique can increase the Raman signals of the analytes owing to the electric field enhancements on the nanostructures. The strong light intensity, called ...photonic nanojet, can be formed at the backlight of the dielectric microstructures. Recently, some researchers have applied the photonic nanojets in SERS. In this paper, a layer of synthesized low-cost polystyrene microspheres with the average of small particle size of 4.26 μm and high refractive index 1.5875 was prepared by dispersion polymerization method and coating on metal nanopillars SERS substrates using air-water interfacial floating method, and it was applied to improve the Raman signal sensitivity of kinetin (6-furfurylaminopurine) which is one kind of plant growth regulators and can function an effective compound for improving plant stress tolerance. The Raman intensity increased from 841 to 4449 for the Raman shift at 1327 cm −1 , about 5.29 times stronger. The SERS experiments using the kinetin of ultralow concentrations are measured and it shows that femto Molar can be measured. The numerical simulations indicated that the enhancement factor was about 4 times for plane wave illumination and 3.1 times for focused Gaussian beam. It has considerable potential for different analytes in sensing applications.
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.
In this study, we report the synthesis and the characterization of poly (vinyl alcohol) based proton conducting membranes. In particular, we describe a novel physically and chemically PVA/HFA (poly ...(vinyl alcohol)/hexafluoroglutaric acid) blending membranes with BASANa (Benzenesulfonic acid sodium salt) and GA (Glutaraldehyde) as binary reaction agents. The key PEM parameters such as ion exchange capacity (IEC), water uptake, proton conductivity, and methanol permeability were controlled by adjusting the chemical composition of the membranes. The IEC value of the membrane is found to be an important parameter in affecting water uptake, conductivity as well as the permeability of the resulting membrane. Plots of the water uptake, conductivity, and methanol permeability vs. IEC of the membranes show a distinct change in the slope of their curves at roughly the same IEC value which suggests a transition of structural changes in the network. The proton conductivities and the methanol permeability of all the membranes are in the range of 10-3-10-2 S cm-1 and 10-8-10-7 cm2 s-1, respectively, depending on its binary crosslinking density, and it shows great selectivity compared with those of Nafion registered -117. The membranes display good mechanical properties which suggest a good lifetime usage of the membranes applied in DMFCs.
Core-shell microspheres have been applied in various research areas and, in particular, they are used in the generation of photonic nanojets with suitable design for photonic applications. The ...photonic nanojet is a narrow and focused high-intensity light beam emitting from the shadow-side of microspheres with tunable effective length, thus enabling its applications in biosensing technology. In this paper, we numerically studied the photonic nanojets brought about from biocompatible hydrogel core-shell microspheres with different optical properties. It was found that the presence of the shell layer can significantly affect the characteristics of the photonic nanojets, such as the focal distance, intensity, effective length, and focal size. Generally speaking, the larger the core-shell microspheres, the longer the focal distance, the stronger the intensity, the longer the effective length, and the larger the focal size of the generated photonic nanojets are. The numerical simulations of the photonic nanojets from the biocompatible core-shell microspheres on a Klarite substrate, which is a classical surface-enhancing Raman scattering substrate, showed that the Raman signals in the case of adding the core-shell microspheres in the system can be further enhanced 23 times in water and 108 times in air as compared in the case in which no core-shell microspheres are present. Our study of using tunable photonic nanojets produced from the biocompatible hydrogel core-shell microspheres shows potential in future biosensing applications.
An amphiphilic, Janus diblock hyperbranched copolyamide was synthesized by the condensation of hydroxyl and carboxyl groups at the focal point of hydrophilic and hydrophobic hyperbranched polyamides, ...respectively, in the presence of a condensation agent. The structure of the self-assembled Janus diblock hyperbranched copolyamide in water at 25 °C, observed by using a transmission electron microscope, consisted of spherical aggregates. As the temperature of the solution was increased, the morphology changed to cylindrical-like aggregates at 50 °C and to dendritic-like aggregates at 70 °C.
An amphiphilic, Janus diblock hyperbranched copolyamide was synthesized by the condensation reaction, and the morphologies of aggregates in water were changed from spherical to dendritic-like structures
via
cylindrical-like structures in response to increasing temperature.
P3HT-P2VP block copolymers were synthesized using anionic macroinitiation of a vinyl end-functionalized P3HT. With different block ratio of P2VP to P3HT, the block copolymers exhibit sphere, ...cylinder, lamellae, and nanofiber nanostructures.
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