Search results for "polymers"
showing 10 items of 3567 documents
2,9-Dimethylpicene: Synthesis, Mutagenic Activity, and Identification in Natural Samples
1990
Abstract 2,9-Dimethylpicene (2,9-DMPic) has been conveniently synthesized via a new route involving oxidative photocyclization of suitable substituted diarylethylenes and has been characterized by high-resolution 400-MHz 1H-NMR spectroscopy. Furthermore, 2,9-DMPic exhibits a typical line narrowed emission spectrum in n-decane matrix frozen at 15 K (Shpol'skii effect). Its unambiguous identification in a natural sample has been performed by this technique, providing strong evidence for the formation of this compound through aromatization of triterpenoid natural precursors. The mutagenicity of this naturally occurring methylated polycyclic aromatic hydrocarbon (PAH) has been examined in six h…
Dynamics of a Spreading Nanodroplet: A Molecular Dynamic Simulation
2003
The spreading of polymer nanodroplets upon a sudden change from partial to complete wetting on an ideally flat and structureless solid substrate has been studied by molecular dynamic simulations using a coarse-grained bead-spring model of flexible macromolecules. Tanner's law for the growth of the lateral droplet radius {R(f) t 0.1 } is found to hold as long as the droplet does not disintegrate into individually moving chains. The data for the contact angle θ following from Tanner's law correspond to a dependence on time {θ(t) t -0.3 }. Our analysis of the mean square displacements of the polymer centers of mass reveals several dynamic regimes during the process of spreading. PACS numbers: …
A comparison of the Raman LAM and electron microscopy in determining crystallite thickness distributions: Polyethylenes with narrow size distributions
1989
Bon accord entre les resultats obtenus pour des polyethylenes cristallises a 118 o C pendant 2 et 20 minutes lorsqu'on prend en compte l'inclinaison de la chaine et pour des polymeres a distribution etroite
Numerical analysis of lamellar thickness distributions
1989
Etude comparative des distributions d'epaisseur de cristallites dans des polyethylenes de masse molaire 10000-100000 cristallises presentant des distributions etroite, bimodale, asymetrique ou large, par microscopie electronique, diffusion RX centrale et spectroscopie Raman. Variations des resultats avec la morphologie des cristallites et surtout avec la nature de la distribution
Active packaging films with natural antioxidants to be used in meat industry: A review.
2018
Spoilage of meat products during processing, distribution and exposure in the markets have an important negative impact on meat industry from an economic point of view. Two of the main problems of meat and products during processing and subsequent storage are lipid oxidation and deterioration due to microorganism growth. In this context, several packaging alternatives have been developed by meat industry in order to limit these losses and to extend the meat products´ shelf life. Over the last years, the use of active packaging has been proposed as an alternative to traditional packaging. The principle of active packaging, particularly antioxidant active packaging, consists of including acti…
Ionic-liquid doped polymeric composite as passive colorimetric sensor for meat freshness as a use case.
2020
Abstract A composite membrane containing 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQS) embedded in an ionic liquid (IL)- polydimethylsiloxane (PDMS)- tetraethyl orthosilicate (TEOS)- SiO2 nanoparticles (NPs) polymeric matrix is proposed. The selected IL was 1-methyl-3-octylimidazolium hexafluorophosphate (OMIM PF6). It is demonstrated that ILs chemical additives of PDMS influenced the sol-gel porosity. The sensor analytical performance for ammonia atmospheres has been tested as a function of sampling time (between 0.5 and 312 h), temperature (25 °C and 4 °C) and sampling volume (between 2L and 22 mL) by means of diffuse reflectance measurements and sensor photos, which can be registe…
Programmable assembly of peptide amphiphile via noncovalent-to-covalent bond conversion
2017
Controlling the number of monomers in a supramolecular polymer has been a great challenge in programmable self-assembly of organic molecules. One approach has been to make use of frustrated growth of the supramolecular assembly by tuning the balance of attractive and repulsive intermolecular forces. We report here on the use of covalent bond formation among monomers, compensating for intermolecular electrostatic repulsion, as a mechanism to control the length of a supramolecular nanofiber formed by self-assembly of peptide amphiphiles. Circular dichroism spectroscopy in combination with dynamic light scattering, size-exclusion chromatography, and transmittance electron microscope analyses r…
Impact of hydrothermal ageing on the thermal stability, morphology and viscoelastic performance of PLA/sisal biocomposites
2016
The influence of the combined exposure to water and temperature on the behaviour of polylactide/sisal biocomposites coupled with maleic acid anhydride was assessed through accelerated hydrothermal ageing. The biocomposites were immersed in water at temperatures from 65 to 85 °C, between the glass transition and cold crystallisation of the PLA matrix. The results showed that the most influent factor for water absorption was the percentage of fibres, followed by the presence of coupling agent, whereas the effect of the temperature was not significant. Deep assessment was devoted to biocomposites subjected to hydrothermal ageing at 85 °C, since it represents the extreme degrading condition. Th…
Magnetic molecularly imprinted polymer for the simultaneous selective extraction of phenoxy acid herbicides from environmental water samples
2022
[EN] A selective magnetic molecularly imprinted polymer (MMIP) was synthetized with 4-chloro-2-methylphenoxyacetic acid as template and 4-vinylpiridine as monomer in presence of vinylized magnetite nanoparticles. Scanning electron microscopy, nitrogen adsorption-desorption isotherms, Fourier transform infrared spectrometry and vibrating sample magnetometry were applied to characterize the resulting material. The synthesized MMIP was applied as sorbent in magnetic molecularly imprinted solid-phase extraction (MMISPE) for selective extraction of a mixture of the five herbicides 4-chloro-2-methylphenoxyacetic acid (MCPA), 4-(4-chloro-2-methylphenoxy)butyric acid (MCPB), mecoprop (MCPP), fenoxa…
Targeted tumor imaging of anti-CD20-polymeric nanoparticles developed for the diagnosis of B-cell malignancies
2015
Sara Capolla,1 Chiara Garrovo,2 Sonia Zorzet,1 Andrea Lorenzon,3 Enrico Rampazzo,4 Ruben Spretz,5 Gabriele Pozzato,6 Luis Núñez,7 Claudio Tripodo,8 Paolo Macor,1,9 Stefania Biffi2 1Department of Life Sciences, University of Trieste, 2Institute for Maternal and Child Health – IRCCS “Burlo Garofolo”, Trieste, 3Animal Care Unit, Cluster in Biomedicine (CBM scrl), Trieste, Italy; 4Department of Chemistry “G. Ciamician”, University of Bologna, Bologna, Italy; 5LNK Chemsolutions LLC, Lincoln, NE, USA; 6Department of Medical, Surgery and Health Sciences, University of Trieste, Trieste, Italy; 7Bio-Target, Inc., University of C…