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1.
Summary A synthetic approach for the preparation of poly(aryl ether amides) has been developed where the generation of an aryl ether
linkage was the polymer-forming reaction. The amide moiety was found to be sufficiently electron withdrawing to activate halosubstituents,
towards nucleophilic aromatic substitution polymerizations, analogous to conventional activating groups (i.e, sulfone, ketone
etc.). Several new A-B monomers, 4-fluoro-N-(4-hydroxyphenyl)benzamide, 1, and 4-fluoro-N-(3-hydroxyphenyl)benzamide, 2, which contain both an amide-activated fluoro group and a phenol group were prepared and their self polymerization studied.
Compounds 1 and 2 were prepared by the condensation of 4-fluorobenzoyl chloride with either 4-or 3-aminophenol, respectively. The polymerizations
were carried out in an N-methyl-2-pyrrolidone (NMP)/N-cyclohexyl-2-pyrrolidone (CHP) solvent mixture in the presence of potassium
carbonate. Several new high molecular weight poly(aryl ethers) were prepared by this route with Tg's in the 225 °C range. 相似文献
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Evran E. Ural Victoria Toomajian Ehsanul Hoque Apu Mladen Veletic Ilangko Balasingham Nureddin Ashammakhi Masamitsu Kanada Christopher H. Contag 《International journal of molecular sciences》2021,22(9)
Extracellular vesicles (EVs) are cell-derived nanostructures that mediate intercellular communication by delivering complex signals in normal tissues and cancer. The cellular coordination required for tumor development and maintenance is mediated, in part, through EV transport of molecular cargo to resident and distant cells. Most studies on EV-mediated signaling have been performed in two-dimensional (2D) monolayer cell cultures, largely because of their simplicity and high-throughput screening capacity. Three-dimensional (3D) cell cultures can be used to study cell-to-cell and cell-to-matrix interactions, enabling the study of EV-mediated cellular communication. 3D cultures may best model the role of EVs in formation of the tumor microenvironment (TME) and cancer cell-stromal interactions that sustain tumor growth. In this review, we discuss EV biology in 3D culture correlates of the TME. This includes EV communication between cell types of the TME, differences in EV biogenesis and signaling associated with differing scaffold choices and in scaffold-free 3D cultures and cultivation of the premetastatic niche. An understanding of EV biogenesis and signaling within a 3D TME will improve culture correlates of oncogenesis, enable molecular control of the TME and aid development of drug delivery tools based on EV-mediated signaling. 相似文献
5.
Pablo Bonilla Joaquim Hernandez Esther Giraldo Miguel A. Gonzlez-Prez Ana Alastrue-Agudo Hoda Elkhenany María J. Vicent Xavier Navarro Michael Edel Victoria Moreno-Manzano 《International journal of molecular sciences》2021,22(11)
We currently lack effective treatments for the devastating loss of neural function associated with spinal cord injury (SCI). In this study, we evaluated a combination therapy comprising human neural stem cells derived from induced pluripotent stem cells (iPSC-NSC), human mesenchymal stem cells (MSC), and a pH-responsive polyacetal–curcumin nanoconjugate (PA-C) that allows the sustained release of curcumin. In vitro analysis demonstrated that PA-C treatment protected iPSC-NSC from oxidative damage in vitro, while MSC co-culture prevented lipopolysaccharide-induced activation of nuclear factor-κB (NF-κB) in iPSC-NSC. Then, we evaluated the combination of PA-C delivery into the intrathecal space in a rat model of contusive SCI with stem cell transplantation. While we failed to observe significant improvements in locomotor function (BBB scale) in treated animals, histological analysis revealed that PA-C-treated or PA-C and iPSC-NSC + MSC-treated animals displayed significantly smaller scars, while PA-C and iPSC-NSC + MSC treatment induced the preservation of β-III Tubulin-positive axons. iPSC-NSC + MSC transplantation fostered the preservation of motoneurons and myelinated tracts, while PA-C treatment polarized microglia into an anti-inflammatory phenotype. Overall, the combination of stem cell transplantation and PA-C treatment confers higher neuroprotective effects compared to individual treatments. 相似文献
6.
Julie Y. Qian Raymond A. Pearson Victoria L. Dimonie Mohamed S. El-Aasser 《应用聚合物科学杂志》1995,58(2):439-448
Poly(butadiene-co-styrene) [P(B-S)] core-poly(methyl methacrylate) (PMMA) shell particles were prepared using a two-step emulsion polymerization. These core-shell particles were used to toughen an epoxy polymer. The role of particle-epoxy interfaces were studied by systematically varying the shell compositions of the core-shell particles such as PMMA, P[MMA-acrylonitrile (AN)], P[MMA-glycidyl methacrylate (GMA)] and P[MMA-divinyl benzene(DVB)]. Therefore, the nature of the particle-epoxy interfaces is varied in terms of physical interactions and chemical bonding. The fracture toughness values of the toughened epoxies were measured using linear elastic fracture mechanics. Results indicate that the morphology of the dispersed particles in the epoxy matrix plays an important role in the toughening of epoxies. This degree of dispersion can be varied by incorporating AN and GMA comonomers in the PMMA shells or by crosslinking the shell. In summary, nanoscale interactions of the rubber-matrix interface do not directly influence fracture toughness, instead, it was found that the nanoscale interactions could be used to control the blend morphology which has a dramatic effect on toughness. © 1995 John Wiley & Sons, Inc. 相似文献
7.
Rana M. Tubaileh Antonio Garrido-Fernández M. Victoria Ruiz-Méndez Manuel León-Camacho Enrique Graciani-Constante 《Journal of the American Oil Chemists' Society》2002,79(1):101-104
Changes in the contents of waxes and fatty alcohols during deodorization/physical refining of bleached olive oil were studied.
Experiments were carried out with 1.85% acidity oil, which was physically refined in a discontinuous deodorizer of 250-kg
maximum capacity using nitrogen as stripping gas instead of steam. The variables studied were load and temperature of oil
in the deodorizer as well as N2 flow. Analyses of waxes and alcohols were carried out at different operation times. The maximum content of wax was always
observed when the oil reached the deodorization temperature. The variation in the wax content depended on temperature and
N2 flow. Wax decomposition started and continued during the operating time, and a progressive decrease, which was pronounced
between 3 and 4 h, was observed. Small changes in waxes were observed between 4 and 5 h. Total content of fatty alcohols diminished
throughout the operating time, and changes did not depend on the variables studied. 相似文献
8.
Ghurmallah H. Al‐Ghamdi E. David Sudol Victoria L. Dimonie Mohamed S. El‐Aasser 《应用聚合物科学杂志》2006,101(6):4504-4516
Miniemulsification technology was used to encapsulate TiO2 particles inside a styrene/n‐butyl acrylate copolymer with high loading levels (11 to 70% PVC (pigment volume concentration)). In this approach, a St/BA copolymer dissolved in toluene in the presence of a costabilizer (hexadecane) was mixed with a dispersion of TiO2 particles in toluene and sonified, and then emulsified in an aqueous surfactant solution by sonification. The effect of sonification time on both the dispersibility of the TiO2 particles in the presence of the copolymer and hexadecane and on the encapsulated particle size was investigated. Particle size analysis by dynamic light scattering showed that these composite latexes are quite stable. It was also found that as the TiO2 loading increased from 11 to 43% PVC, the particle size of the TiO2 dispersion decreased while the polymer‐encapsulated TiO2 particle size increased. The effect of surfactant concentration (sodium lauryl sulfate, SLS) on the encapsulated particle size was investigated using four different SLS concentrations in the 11% PVC system. The results showed that as the SLS concentration increased the particle size decreased, as expected. Also it was found that the minimum surfactant concentration that gives stable encapsulated TiO2 particles is above 10 mM SLS. The role of HD in the recipe was studied for an artificial latex containing no TiO2 and one prepared at 11% PVC, in terms of particle size before and after solvent stripping, and its effect on the Tg. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4504–4516, 2006 相似文献
9.
The sedimentation behavior of alumina powder has been studied in the presence of poly-vinylpyrrolidone (PVP) and poly(vinylpyrrolidone-co-vinyl acetate) (PVP/VA) in both thermodynamically “good” and “poor” solvents for the PVP homopolymer. PVP/VA provides higher sediment densities than does its PVP homopolymer counterpart. Solutionstate 13C-T1 spin-lattice relaxation measurements were made on analogous mixtures both with and without alumina powder. The NMR results suggest that the PVP/VA copolymer is anchored to the alumina powder surface by means of VA moieties, whereas the PVP moieties extend into the continuous phase of the slurry medium. Thus, the higher settling densities that are observed in the presence of PVP/VA can be attributed to a steric stabilization mechanism. © 1993 John Wiley & Sons, Inc. 相似文献
10.
Novel imide-aryl ether benzoxazole copolymers were prepared and their morphology and mechanical properties investigated. A key feature of these copolymers is the incorporation of a benzoxazole moiety by the use of 2,2′-bis[4-(3-aminophenoxy)phenyl]-6,6′-bibenzoxazole or 2,2′-bis[4-(4-aminophenoxy)-phenyl]-6,6′-bibenzoxazole as co-diamines in polyimide syntheses. The preparation of these diamines involved the nucleophilic aromatic substitution of 2,2′-bis(4-fluorophenyl)-6,6′-bibenzoxazole with either 3- or 4-aminophenol in the presence of K2CO3. The diamines were co-reacted with various compositions of pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) to synthesize the desired poly(amic acids). Films were cast and cured (350°C) to effect the imide formation, affording films with elongations between 40 and 110% and moduli in the 2000–2750 MPa range. The copolymers exhibited good dimensional (Tg in excess of 300°C) and thermal stability. Wide-angle X-ray diffraction measurements on the copolymers showed that the ordered morphology characteristic of PMDA/ODA polyimide was retained. Improvements in the auto-adhesion were observed, particularly in those copolymers which displayed a Tg. 相似文献