Comparison of cellulose and chitin nanocrystals for reinforcing regenerated cellulose fibers

In this study, regenerated cellulose fibers reinforced by cellulose nanocrystals (CENC) and chitin nanocrystals (CHNC) were prepared by blending the nanocrystals suspensions with the cellulose solution in NaOH/urea/water solvent at room temperature. The effect of nanocrystals' addition on the properties of spinning dopes and regenerated fibers were investigated and compared. Results showed that the obtained CENC and CHNC had different dimensions, and both of them increased the viscosity and decreased the transparency of the spinning dopes. However, the dissolution state of cellulose was not changed. CHNC had a greater influence on the properties of spinning dopes, while CENC had more obvious effect on the performance of regenerated fibers. The CENC reinforced fibers showed a higher crystallinity index as compared to the CHNC reinforced fibers. The tensile strength of the regenerated fibers was evidently improved when 3 wt % CENC or 2 wt % CHNC were added, while the elongation at break of the fibers was slightly decreased with the increase of nanocrystals content. The morphology and thermal stability of the regenerated fibers was not affected by the addition of nanocrystals. This study suggested that the dimension, group and content of nanocrystals were important factors for the reinforcement of regenerated cellulose fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44880.     

Phosphate ester side‐chain‐modified conjugated polymer for hybrid solar cells

Although nanocrystals have several advantages of tunable bandgap and high carrier mobility, it is still challenging to achieve high‐performance polymer: nanocrystals hybrid solar cells (HSC) due to the complicated surface problem. Many efforts have been devoted to replace the long alkyl chain on the surface of nanocrystals to improve the charge transfer and transport. Herein, we modified the alkyl chain in poly[2,6–(4,4‐bis (2‐ethylhexyl)?4H‐cyclopenta[2,1‐b;3,4‐b′]‐dithiophene)‐alt ‐4,7–(2,1,3‐benzothiadiazole)] (PCPDTBT) by phosphate ester. Due to its strong affinity to CdSe nanocrystals, the resulting polymers can spontaneously exchange the long chain ligands in one‐step process. With the improved morphology of polymer: CdSe blended film, a power conversion efficiency (PCE) of 3.12% was achieved for hybrid solar cells. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45003.     

Poly(vinyl alcohol)/CaCO3‐diacid nanocomposite: Investigation of physical and wetting properties and application in heavy metal adsorption

Poly(vinyl alcohol) (PVA) nanocomposite and modified CaCO₃ nanoparticles (NPs) were fabricated by ultrasound agitation method with particle content altering from 3, 5, and 8 wt %. The CaCO₃ surface was successfully treated by 10 wt % of bioactive dicarboxylic acid (DA). The influences of loading modified NPs on the thermal, mechanical, adsorption, contact angle, and physical properties of the poly(vinyl alcohol) nanocomposite films were thoroughly studied. The results showed that incorporation of modified CaCO₃ into the PVA matrix had better performance than the pure PVA. Meanwhile, tensile strength, Young's modulus, and thermal stability are enhanced from 33.36 MPa, 1.26 GPs, and 242.918C (neat PVA) to 81.7 MPa, 4.81 GPa, and 312.95 °C (PVA/CaCO₃‐DA NC 5 wt %), respectively. Also, the adsorption capacity of the PVA/CaCO₃‐DA NCs 5 and 8 wt % revealed that the NC films could act as an appropriate absorbent for the removal of Cd(II) ions with maximum adsorption capacity of about 20.70 and 25.19 mg g^?1 for Cd(II), respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45414.     

Dual‐bonding structured ternary composite film of poly(vinyl alcohol)–boric acid–nanodiamond

Ternary composite films of poly(vinyl alcohol) (PVA), boric acid (BA), and detonation nanodiamond (DND) were prepared by aqueous solution method. Because of its excellent mechanical/thermal properties and low friction coefficient, DND is expected to offer PVA film superior performance if the puzzles of particle agglomeration in polymer matrix and fragile interface reaction between DND and PVA can be settled. BA was used as a crosslinking agent to form a strong network structure between DND and PVA. Investigation on microstructure of PVA/BA/DND films and bonding mechanisms therein shows that BA, DND, and PVA may crosslink by oxo‐bridges owing to the interaction of hydroxyl groups. The Young's modulus (E) of composite films was enhanced by nearly 3.3 times with only 0.8 wt % DND loading, and the antiwear, thermal stability, and waterproof properties can be significantly improved after the crosslinking. Meanwhile, the transparency of composite films can be well preserved even with large DND content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45449.     

Nanocomposite materials based on zinc sulfide nanoparticles reinforced chlorinated styrene butadiene rubber

The effect of zinc sulfide (ZnS) nanoparticles in chlorinated styrene‐butadiene rubber (Cl‐SBR) was analyzed by X‐ray diffraction analysis (XRD), scanning electron microscopy (SEM), Differential Scanning Calorimetry, and impedance analyzer. The cure time, mechanical properties, and solvent transport of petroleum fuels through the Cl‐SBR/ZnS nanocomposites at different temperatures were evaluated. XRD and SEM studies showed that ZnS nanoparticles were well‐placed in the polymeric structure of Cl‐SBR. The increased glass transition temperature of the composite with the loading of nanoparticles indicated the increased molecular rigidity. Rheometric torque, alternating current conductivity, dielectric property, tensile strength, tear resistance, modulus, hardness, abrasion resistance, heat build‐up, and compression set were increased with the loading of nanoparticles, however, cure and scorch time, elongation at break, and resilience were reduced with the loading of nanoparticles. The diffusion results have been explained in terms of the size of liquid molecules and the diffusion mechanism was found to follow the anomalous trend. The activation energy for diffusion, sorption and permeation process was evaluated. These activation energy parameters were increased with the size of the penetrant molecules and also with the loading of nanoparticles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46538.     

Polarity‐reversal‐producing phase transfer of hydrophilic silver nanoclusters capped by a hyperbranched polymer from water to nonpolar organic solvents

Hyperbranched poly(ethylene imine) (PEI)‐capped Ag nanoclusters, synthesized starting from an aqueous environment, dispersed well in water and most polar organic solvents. However, with the addition of 1,4‐dioxane, the PEI‐capped Ag nanoclusters could be separated completely to obtain hydrophilic and hydrophobic Ag nanoclusters. Through this facile method, the successful phase transfer of PEI‐capped Ag nanoclusters from the aqueous phase to the nonpolar organic phase, such as from water to carbon tetrachloride, chloroform, and methylene bichloride, was easily realized. The polarity reversal of Ag nanoclusters were considered to be associated with the conformational change of PEI on the basis of the hydrophobic methylene groups of polymer backbone facing the external side or internal side, and this polarity reversal was irreversible. Moreover, PEIs with higher molecular weights showed a higher efficiency of phase transfer of the Ag nanoclusters. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43206.     

Enhanced water flux through ultrafiltration polysulfone membrane via addition‐removal of silica nano‐particles: Synthesis and characterization

In the present paper, hierarchically structured ultrafiltration polysulfone (PSf) membrane was prepared to explore the effect of addition and subsequent removal of SiO₂ nano‐particles on the membrane morphology, hydrophilicity, and separation properties. The PSf based membranes namely PSf, PSf/SiO₂ and PSf/WSiO₂ (i.e. SiO₂ nano‐particles was acid‐washed and removed from PSf/SiO₂), were synthesized and characterized by different characterization methods. Pure water flux through the membranes was determined using a filtration unit operating at a continuous dead‐end flow mode. The modification enhanced the morphology, hydrophobicity, porosity and transport properties of the modified membranes, although the molecular weight cut‐off (MWCO) of the membranes was not changed considerably. In comparison, PSf/WSiO₂ membrane exhibited excellent pure water flux (about 4.5 times the flux of PSf, and 17 times the flux of PSf/SiO₂), although antifouling property of PSf/SiO₂ in separation of bovine serum albumin (BSA) was better than that of PSf and PSf/WSiO₂ membranes. The results suggested that the addition/removal of sacrificial solid fillers within/from a membrane matrix may provide a promising strategy to enhance PSf membrane transport property. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43556.     

Size‐controlled gold nanoparticles inside polyacrylamide microgels

Gold nanoparticles (AuNPs) of different sizes were synthesized into a crosslinked network of polyacrylamide (PAAm) microgels. PAAm was prepared by means of semicontinuous inverse heterophase polymerization under monomer‐starving conditions with a z‐average particle size of 384 ± 18 nm. AuNPs with controlled size were obtained by a reduction reaction of Au⁺³ to Au⁰ from a gold(III) chloride trihydrate (HAuCl₄) solution inside microgel the crosslinked network (AuNP‐PAAm). The reduction reaction was verified for 2 h by ultraviolet–visible spectroscopy (UV–vis). AuNP–PAAm exhibited a particle size between 288 ± 12 and 230 ± 15 nm at HAuCl₄ concentrations of 0.4 and 1.3 mM, respectively. The AuNP–PAAms were observed by transmission electron microscopy, and their sizes were determined to be 19 ± 2 nm (1.3 mM) and 17 ± 2 nm (1.1 mM). With UV–vis spectroscopy, we detected the formation of AuNPs at a wavelength of 552 nm, and with X‐ray diffraction analysis, we proved that the crystal arrangement was face‐centered cubic. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43560.     

Preparation and application of tectoridin‐imprinted magnetite nanoparticles

In this work, the tectoridin‐imprinted magnetite nanoparticles (TIMNPs) were firstly prepared by using tectoridin as template molecule, methacrylic acid as functional monomer, styrene as crosslinking agent, and superparamagnetic Fe₃O₄ particles as magnetic component. TIMNPs with a size of about 161 nm were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), vibrating sample magnetometer (VSM), and thermogravimetric analysis (TGA). Rebinding experiments were carried out to determine the specific binding properties and adsorption selectivity. The maximum number of binding sites was 69.58 μmol/g and there was only one kind of binding sites existed in TIMNPs. The relative separation factors for tectoridin with its analogues such as baicalin and atenolol were 2.63 and 2.66, respectively. The results indicated that the synthesized TIMNPs had excellent saturation magnetization, binding capacity, and absorption selectivity. TIMNPs could be one of the most promising candidates for tectoridin extraction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43806.     

Epoxy resin‐based ultrafine dry powder coatings for implants

Ultrafine dry powder coating technology creates biocompatible polymeric coatings for implants. Nanoparticles (nTiO₂) modify flow to prevent agglomeration and create homogenous coatings. Since polyester‐based coatings require the potentially harmful 1,3,5‐triglycidyl isocyanurate (TGIC) curing agent, this study's objective was to develop alternative TGIC‐free formulations. Epoxy and epoxy/polyester (1:1) hybrid mixtures were enriched with CaO (5% w/w) and nTiO₂ (0.5% w/w), as functional additives and flow modifiers, respectively. Epoxy‐TiO₂ and Hybrid‐TiO₂ mixtures were prepared with micron‐sized TiO₂ (25% w/w) to enhance biocompatibility. Polymer chips and additives were combined in a high‐shear mixer and passed through a sieve (35 µm) to yield ultrafine particles that were sprayed (20 kV) onto metal sheets and cured (200 °C). Particle size analyses showed that all formulations were ultrafine (D 0.5 < 35 µm), and epoxy/polyester/TiO₂ mixtures were the smallest (D 0.5 = 16.34 µm). Angles of repose, avalanche and resting indicated reduced flowability when epoxy was enriched with TiO₂ and/or polyester, although all formulae were highly flowable. Elemental mapping of coatings showed a predominance of carbon (C) and oxygen (O) from resin polymer, and elevated titanium (Ti) in the TiO₂ enriched surfaces. However, calcium (Ca) clusters were higher on the epoxy/polyester Hybrid coatings. Optical microscopy showed human mesenchymal cells (ATCC CRL‐1486) attached and spread out, and Alizarin Red staining showed mineral deposits in 2–4 week cultures, particularly on epoxy/polyester/TiO₂ Hybrid surfaces. These epoxy resin‐based formulations were effective TGIC‐free substitutes for ultrafine dry powder coatings on implants. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43960.