Surface functionalized single-walled carbon nanotubes (SWCNT) with 4-(azidomethyl) styrene were prepared through [2 + 1] nitrene cycloaddition reaction. 53 molecules of (4-vinylbenzyl) per 1000 carbon atoms were obtained. Sidewall covalent functionalization was confirmed by spectroscopic techniques (FTIR, Raman, and XPS) and TGA. According to Raman and XRD spectroscopy, the integrity of the CNT was preserved, suggesting that the aziridine rings help to restore the aromaticity over the CNT structural defects. The reactive styrene moiety on (4-vinylbenzyl) aziridine-SWCNT was reacted with PDMS during the cross-linking process with vinyl or aryl peroxides (dicumyl peroxide (DCP), (T29) or (T145) from Akzo Nobel Chemicals). Testing specimens of composites integrated by 0.7 grams of (4-vinylbenzyl) aziridine-SWCNT per one hundred grams of PDMS were obtained according to ASTM D-624 standard method after its processing in an open roller mill followed by compression molding. When compared to the PDMS vulcanization, up to 35% reductions in vulcanization time (v.t.) were observed with the use of (4-vinylbenzyl) aziridine-SWCNT as a reactive filler. Improvements in their mechanical properties, up to 75% of tensile strength, 85% elastic limit, 40% in tear strength, and 35% in Shore A hardness were observed when PDC was used and compared with neat PDMS vulcanized with the same crosslinking agent. Among all the (4-vinylbenzyl) aziridine-SWCNT-PDMS composites formulated, those obtained with T145 or DCP (2.5 phr) exhibited the highest level of improvement in both v.t. and physics-mechanical properties. These findings open new opportunities to apply carbon nanostructures as a reactive filler in the construction of conductive or piezoresistive flexible stretchable devices.Highlights PDMS OP vulcanization with reactive (4-vinylbenzyl) aziridine-SWCNT. Sidewall functionalization of SWCNT with (4-azidomethyl) styrene. SWCNT sidewall functionalization through [2 + 1] nitrene cycloaddition. Fully spectroscopic characterization of (4-vinylbenzyl) aziridine-SWCNT. Significant mechanical performance improvements with PDMS-SWCNT nanocomposites.

In this study, the effect of single-walled carbon nanotubes (SWCNTs) on the cross-linking of natural rubber (NR) using organic peroxides was investigated. NR-SWCNTs nanocomposites were prepared in an open two-roller mill followed by vulcanization with the compression molding process. Three different organic peroxides, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (T29), dicumyl peroxide (DCP), and 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne (T145), were used as vulcanizing agents. SWCNTs promote a remarkable reduction in the vulcanization time and increase the degree of cross-linking of vulcanized rubber when compared with neat or natural rubber–carbon-black composites; the same tendency was obtained in the NR-SWCNTs vulcanized with sulfur. Additionally, the mechanical performance of the NR-SWCNTs composites was significantly improved up to 75, 83, 27, and 10% for tensile strength, moduli, tear strength, and hardness. Raman spectroscopy studies evidence the occurrence of reaction between nanotube walls and free radicals generated from using organic peroxides during the vulcanization process. These results demonstrate that the incorporation of SWCNTs in combination with the use of organic peroxides for the NR vulcanization represents a potential alternative for the improvement of the physicochemical properties of NR composites.

The leaves of two ethnotaxa of Agave karwinskii Zucc., 'Cuishe' and 'Madrecuishe', were analyzed using field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to characterize their occurring biominerals. The sharp and high peak at 2θ 21.4° in the XRD patterns and the prominent bands' envelopes related to aluminosilicates in the FTIR spectra showed the occurrence of chantalite in the leaves of both ethnotaxa. For the first time, chantalite is reported as a biomineral occurring naturally in Agave plants. The FE-SEM/EDX results revealed needle-shaped calcium oxalate profusely dispersed near the upper epidermis, in addition to uncovering the presence of calcium carbonate and silica in particles of irregular shape. Intriguingly, the occurrence of both minerals in Agave plants has not been reported either, suggesting complex biomineralization patterns in Agave karwinskii. It is proposed that calcium carbonate in the leaves of Agave is formed by the reaction of chantalite with CO2.

We report the synthesis of poly(styrene-block-lactic acid) (PS-b-PLA) copolymers with triazole rings as a junction between blocks. These materials were prepared via a ‘click’ strategy which involved the reaction between azide-terminated poly(styrene) (PS-N3) and acetylene-terminated poly(D,L-lactic acid) (PLA-Ac), accomplished by copper-catalyzed azide-alkyne cycloaddition reaction. This synthetic approach has demonstrated to be effective to obtain specific copolymer structures with targeted self-assembly properties. We observed the self-assembly behavior of the PS-b-PLA thin films as induced by solvent vapor annealing (SVA), thermal annealing (TA), and hydrolysis of the as-spun substrates and monitored their morphological changes by means of different microscopic techniques. Self-assembly via SVA and TA proved to be strongly dependent on the pretreatment of the substrates. Microphase segregation of the untreated films yielded a pore size of 125 nm after a 45-min SVA. After selectively removing the PLA microdomains, the as-spun substrates exhibited the formation of pores on the surface, which can be a good alternative to form an ordered pattern of triazole functionalized porous PS at the mesoscale. Finally, as revealed by scanning electron microscopy–energy dispersive X-ray spectroscopy, the obtained triazole-functionalized PS-porous film exhibited some affinity to copper (Cu) in solution. These materials are suitable candidates to further study its metal-caption properties.

The use of [2 + 1] cycloaddition microwave-assisted reaction as an effective and versatile method for the surface covalent functionalization of single-wall carbon nanotubes (SWCNTs), graphene nanoplates (GNP) and carbon nanofibers (CNF) was studied through the reaction with 4-(azidomethyl) benzoic acid (4-AMBA). Thermal Gravimetric Analysis (TGA) and X-Ray Diffraction (XRD) confirm the successful covalent functionalization with the presence of the organic compound. FTIR spectroscopy and X-Ray Photoelectron spectroscopy (XPS) reaffirm the union between the 4-AMBA and the carbon nanostructures by observing the C–N bond of the formed aziridine ring. Raman spectroscopy and Transmission Electron Microscopy (TEM) reveal the integrity of the graphitic structure after the functionalization process.

A versatile approach towards porous polystyrene-based frameworks functionalized with triazolyl moieties is reported. These porous materials were prepared from poly(D,L-lactic acid)-block-poly(styrene-stat-4-azidomethylstyrene) (PLA-b-P(S-stat-4-AMS)) diblock copolymer precursors. Upon macroscopic orientation and subsequent alkaline hydrolysis of the PLA block, such triazolyl-containing porous polystyrenes were produced. Experimentally, a PLA macroinitiator was synthesized by ring-opening polymerization (ROP) of D,l-lactide using a heterobifunctional initiator. The prepared macroinitiator containing a terminal tertiary α-bromo ester group allowed for further ATRP statistical copolymerization of styrene and 4-azidomethylstyrene, affording the second block, i.e. the P(S-stat-4-AMS) block. The styrene to 4-azidomethylstyrene molar ratio was tuned to obtain various compositions of the hydrophobic block. PLA macroinitiators and corresponding PLA-b-P(S-stat-4-AMS) diblock copolymers were fully characterized by size exclusion chromatography (SEC), 1H and 13C nuclear magnetic resonance (NMR), Fourier Transform Infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). Functionalization of PLA-b-P(S-stat-4-AMS) diblock copolymers with p-tolylacetylene or 2-methyl-3-butyn-2-ol was carried out via copper-catalyzed azide-alkyne cycloaddition (CuAAC), yielding triazole ring in high yields (>90%). Finally, the porous structure of such functional polystyrene frameworks was examined by scanning electron microscopy (SEM).

Product miniaturization is a constant trend in industries that demand ever-smaller products that can be mass produced while maintaining high precision dimensions in the final pieces. Ultrasonic micro injection molding (UMIM) technology has emerged as a polymer processing technique capable of achieving the mass production of polymeric parts with micro-features, while still assuring replicability, repeatability, and high precision, contrary to the capabilities of conventional processing technologies of polymers. In this study, it is shown that the variation of parameters during the UMIM process, such as the amplitude of the ultrasound waves and the processing time, lead to significant modification on the molecular structure of the polymer. The variation of both the amplitude and processing time contribute to chain scission; however, the processing time is a more relevant factor for this effect as it is capable of achieving a greater chain scission in different areas of the same specimen. Further, the presence of polymorphism within the samples produced by UMIM is demonstrated. Similarly to conventional processes, the UMIM technique leads to some degree of chain orientation, despite the fact that it is carried out in a relatively small time and space. The results presented here aim to contribute to the optimization of the use of the UMIM process for the manufacture of polymeric micro parts.

Esters of 2-bromo-2-methylpropanoate of poly(oxyalkylene) polymers such as poly(ethylene glycol) or α-methyl poly(ethylene glycol) were prepared in high yields and characterized by spectroscopic and chromatographic methods (NMR, FT-IR, mass spectroscopy and SEC). The halogen chain-end group in the poly(oxyalkylene) bromine-terminated esters was characterized by MALDI-TOF MS. The effect of the solvents (methanol or tetrahydrofuran) and the cationic agents such as silver trifluoroacetate (AgTFA), silver trifluoromethanesulfonate (AgTFS) and sodium trifluoroacetate (NaTFA) on the mass spectra was studied. Analysis of the mass spectra demonstrated that the analyte was transformed to unsaturated (elimination), alkoxy or hydroxyl end-groups (substitution) molecules when silver cationic agents were used; these results were also supported by 1H NMR study. When sodium salt was used as a cationic agent, well-defined bromine-terminated macromolecules were successfully determined through MALDI-TOF MS. Well-characterized esters of 2-bromo-2-methylpropanoate of poly(oxyalkylene) polymers could be used as ATRP macroinitiators for the synthesis of a variety of polymeric architectures of interest as drug delivery bioconjugates.

Self-crosslinking styrene-acrylic latexes functionalized with 3-isopropenyl-α,α-dimethyl benzyl isocyanate (TMI) by semibatch emulsion polymerization were prepared. Polymerizations were performed in emulsions with aerosol EF-800 surfactant; remarkable colloidal stability of the copolymer latexes was measured in fresh and aged samples. The effects on film formation, tensile properties, permeability to water vapor, and oxygen were evaluated by varying the TMI concentrations (from 0 to 6 wt%). The obtained latexes were used as binder to prepare water-based coatings, which were applied on steel specimens; hydrolysis of TMI acts as a self-crosslinked promoter once the film was applied. Adhesion tests, scratch hardness, and gloss properties were evaluated. Water vapor permeability of latex films

ABSTRACTA novel configuration of bilayer composite sheets containing different polymers is described and used for the first time in the single point incremental forming (SPIF) process. These bilayer sheets made of polypropylene (PP) and Santoprene are fabricated by hot welding, and shaped with cone‐like geometry by SPIF. The bilayer configuration is such that only one of the containing polymers is in contact with the forming tool. During the SPIF processing, the bilayer sheets show a noticeable difference in the mechanical response, depending mainly on the polymer that is not in contact with the forming tool, which is related to a lower polymer softening. The performance of the bilayer sheets is compared against the neat polymers and a blend of these with a mass ratio of 1:1. The observed effect is introduced as a dual effect of properties that brings together in a single composite sheet, properties for a better performance in SPIF and wider functionality of the fabricated parts, evidenced by a lower material softening and higher mechanical strength, in comparison with the two individual polymers, and even better than the blend of both. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47093.

Fluorescent nanohybrids materials were fabricated from organosilane-functionalized halloysite nanotubes (HNTs), covalently bonded to new mixed-valence Cu(I,II) complex (CuCuII)-Cu-I (HOBt)(2)center dot CH3OH (HOBt = 1-hydroxybenzotriazole)]. Morphology, composition and optical properties of nanohybrids were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDXS), Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and steady-state fluorescencec. The copper (I, II) complex was also characterized for the sake of comparison. Molecular immobilization and molecular geometry changes due to halloysite environment changed the photoluminescence behavior of the copper (I,II) complex, allowing HNTs-g-(CuCuII)-Cu-I(HOBt)(2)center dot CH3OH nanohybrids to display a tri-component light as observed by fluorescence microscopy, making them an interesting option for attaining white light. (C) 2018 Elsevier B.V. All rights reserved.

Sheets of polycaprolactone (PCL) and ultra-high molecular weight polyethylene (UHMWPE) were fabricated and shaped by the Single-Point Incremental Forming process (SPIF). The performance of these biocompatible polymers in SPIF was assessed through the variation of four main parameters: the diameter of the forming tool, the spindle speed, the feed rate, and the step size based on a Box–Behnken design of experiments of four variables and three levels. The design of experiments allowed us to identify the parameters that most affect the forming of PCL and UHMWPE. The study was completed by means of a deep characterization of the thermal and structural properties of both polymers. These properties were correlated to the performance of the polymers observed in SPIF, and it was found that the polymer chains are oriented as a consequence of the SPIF processing. Moreover, by X-ray diffraction it was proved that polymer chains behave differently on each surface of the fabricated parts, since the chains on the surface in contact with the forming tool are oriented horizontally, while on the opposite surface they are oriented in the vertical direction. The unit cell of UHMWPE is distorted, passing from an orthorhombic cell to a monoclinic due to the slippage between crystallites. This slippage between crystallites was observed in both PCL and UHMWPE, and was identified as an alpha star thermal transition located in the rubbery region between the glass transition and the melting point of each polymer.

Unaligned and aligned poly(9-vinylcarbazole) (PVK)/NaEu(TTA)4 (TTA=2-thenoyltrifluoracetone) composite fibers were prepared by electrospinning, using tetrahydrofuran (THF) and 1,2-dichoroethane (DCE) as solvents. Scanning electron microscopy (SEM) measurements showed that aligned fibers were wider and thicker than unaligned fibers. Characterization by Fourier transform-infrared (FTIR) spectroscopy indicated that there were weak interactions between PVK and NaEu(TTA)4. Alignment of composite fibers promoted packing of the molecules of the Eu(III)-complex, increased the population of fully overlapping carbazoles (f-PVK) and decreased the asymmetric ratio (R) of the NaEu(TTA)4, leading to less efficient energy transfer and lower lifetimes, as determined using steady-state and dynamic fluorescence spectroscopy. Yet, shorter lifetimes as compared to NaEu(TTA)4 in powder form were found in unaligned and aligned electrospun fibers, ascribed mainly to introduction of defect states during electrospinning. Unaligned electrospun PVK fibers doped with loosen packed europium complexes preferably could be used as promising luminescence materials.

Ultrasonic micro injection molding was confirmed to be an efficient processing technique for the fabrication of a well-filled miniaturized dog-bone shaped specimen of ultra-high molecular weight polyethylene (UHMWPE). The influence of four process parameters on the filling phase of the reduced-size cavity was then analysed. It was established that it is possible to fabricate well-defined specimens when the highest ultrasonic amplitude is applied intermittently at specific intervals during the ultrasonic process to small compacted irregularly shaped UHMWPE samples and the mold temperature is set to 100°C. GPC results showed a decrease in the molecular weight, which was the greatest when 100% of the ultrasonic amplitude was applied. The degree of crystallinity of the processed sample was increased because the reduction of the molecular weight. TGA showed that the thermal stability of UHMWPE fabricated by ultrasonic processing was not significantly influenced by the decrease in the molecular weight. FTIR spectra indicated oxidative degradation in three different regions of the processed UHMWPE specimen. Additionally, the band identified at the wavenumber 910cm−1 indicated a chain scission phenomenon the polymer experienced during the ultrasonic processing.

Novel imidazoline-functionalized diblock copolymers based on polystyrene (PS) and poly(D,L-lactide) (PLA) were synthesized as precursors to corresponding functional PS-based porous materials through a three-step sequential methodology starting from an asymmetric heterobifunctional initiator. α-Hydroxyl poly(4-cyanostyrene-co-styrene) random copolymers were first obtained via an atom transfer free-radical polymerization (ATRP) procedure by varying the amount of 4-cyanostyrene in the comonomer feed. Cyano groups were then transformed into corresponding imidazoline rings. Subsequently, the microwave-assisted ring-opening polymerization (ROP) of d,l-lactide from the imidazoline-functionalized PS-based macroinitiators allowed for the generation of semi-degradable diblock copolymers with different PLA volume fractions so as to develop microphase-separated morphologies. The precursors and resulting copolymers were analyzed by 1H, 13C NMR, and FT-IR spectroscopy. Upon induced shear-flow via channel-die processing, oriented materials constituted of PLA nanodomains in a polystyrene-based continuous matrix were formed. Hydrolysis in alkaline conditions of the PLA sacrificial block yielded imidazoline-functionalized porous PS-based matrices. The resulting porous frameworks were analyzed by scanning electron microscopy (SEM) and nitrogen sorption porosimetry.

Polypropylene-based composites filled with different amounts of functionalized multi-wall carbon nanotubes (f-MWCNTs) were prepared using a melt mixing process, and were shaped by single point incremental forming process (SPIF). The performance of these composite materials when processed by SPIF indicated that the presence of small quantities (<1wt%) of f-MWCNTs leads to a mechanical reinforcement of the polymer matrix, without affecting its formability. This reinforcement was further highlighted due to the alignment of the polymer chains and nanotubes caused by the forming process. A variation in color between the inner and outer sides of the deformed parts revealed the presence of crazing, associated to the different forces exerted on each side. The dispersion of the f-MWCNTs and the polymer-nanotube interaction in the composites were studied by different characterization techniques, and it was found that a good integration of the f-MWCNTs into the polymer matrix was achieved.

Incremental Sheet Forming (ISF) technology is used to manufacture customized products and its application to metallic prosthesis manufacturing has been already tested. However, the use of thermoplastic sheets as raw material in ISF is still reduced and therefore the manufacturing of polymer prosthesis by this technology too. In this framework, the objective of the present paper is to obtain a real cranial geometry of a feasible prosthesis manufactured by ISF using a biocompatible polymer. The real geometry of a cranial fracture is acquired from a computer tomography and treated until get a CAD model. From it, the trajectories have been defined and the cranial geometry manufactured.