Search results for "styren"

Zur Autoxydation von Polystyrol

1971

Die mit Azoisobuttersauredinitril (AIBN) initiierte Autoxydation von Polystyrol (PS) in Chlorbenzol bei 60°C ist von der Ordnung 0,75, bezogen auf AIBN, und 0,34, bezogen auf PS. Der niedrige Exponent der Polystyrolkonzentration weist neben intermolekularen Wachstumsschritten auf intramolekulare Reaktionsschritte bei der Autoxydation hin. Die bei der Autoxydation am Polystyrol gebildeten Hydroperoxidgruppen zerfallen in Essigsathylester als Losungsmittel mit einer Aktivierungsenthalpie von 19,7 kcal/Mol und einer Aktivierungsentropie von −29 cal/Mol Grad. Das spricht fur einen monomolekularen bifunktionellen Zerfallsmechanismus. Als fluchtige Produkte bei diesem Hydroperoxidzerfall werden P…

Sedimentation of dissolved macromolecules in the vicinity of the consolute point 1. Strictly binary systems and kinetic considerations

1986

This paper analyzes the effect of gravity on polymer solutions near the consolute point. Calculations are carried out for monodisperse polystyrene in cyclohexane using the Flory-Huggins expression with a concentration-dependent interaction parameter for the free energy of mixing. Depending on molecular weight and distance to the demixing temperature, the influence of gravity leads to non-negligible gradients of the volume fraction in the one-phase region as well as in the two-phase region. In particular, the effect of gravity on the measurement of the coexistence curve in a finite sample is calculated explicitly.

Compatibility between polystyrene copolymers and polymers in solution via hydrogen bonding

2006

Abstract It has been applied the concept of improving miscibility, by introducing and optimizing the extent of intermolecular hydrogen-bonding interactions between two polymers. We select a commodity polymer such as polystyrene, to study the compatibility in chloroform with poly(vinyl pyridine) and poly(vinyl pyrrolidone), both considered as proton acceptors. In order to enhance polymer–polymer miscibility, polystyrene is slightly modified by copolymerization with methacrylic acid, in the first case, and with vinyl-phenol comonomer, in the second one. In this way, two series of polystyrene-based copolymers are synthesized and characterized bearing ca. 8% (w/w) of –OH groups. The miscibility…

Demixing of unsheared and sheared solutions of polystyrene in tert-butylacetate and the pressure influence on their flow behaviour

1979

For the system tert-butyl acetate/polystyrene (M= 670000) the phase separation behaviour (upper critical solution temperatures, upper critical solution pressures) is investigated by means of visual and turbidimetric cloud-point measurements and by viscometry. For near-critical concentrations the visually determined cloud-points are found at higher, for low concentrations at lower temperatures as compared with the turbidimetrically determined binodal temperature,Tbin Plots of the invers of the turbidity measured atTbin as a function of the polymer concentration,w2, yield a minimum from which the critical composition can be determined. The viscometrically obtained demixing points (break-down …

1992

Semi-IPN's of different composition, based on linear poly(methyl vinyl ether) (PVME) and crosslinked polystyrene are studied using stress and birefringence measurements in simple elongation. From quasistatic stress-strain experiments at constant T(experiment)-Tg, it can be deduced that the stress results only from the deformation of the polystyrene network, while the PVME chains do not contribute to the macroscopic stress. The concentration dependence of the network modulus is adequately described by the rubber elastic theories

Rapid formation of plasma protein corona critically affects nanoparticle pathophysiology

2013

In biological fluids, proteins bind to the surface of nanoparticles to form a coating known as the protein corona, which can critically affect the interaction of the nanoparticles with living systems. As physiological systems are highly dynamic, it is important to obtain a time-resolved knowledge of protein-corona formation, development and biological relevancy. Here we show that label-free snapshot proteomics can be used to obtain quantitative time-resolved profiles of human plasma coronas formed on silica and polystyrene nanoparticles of various size and surface functionalization. Complex time- and nanoparticle-specific coronas, which comprise almost 300 different proteins, were found to …

Cationic and Zwitterionic Polymerizable Surfactants:  Quaternary Ammonium Dialkyl Maleates. 1. Synthesis and Characterization

1999

Cationic and zwitterionic reactive dialkyl maleates with different hydrophobic chain lengths (R = C10H21, C12H25, C16H33, and C18H37), and some similar surfactants without double bonds were synthesized with an aim to use them as stabilizers in the batch and seeded emulsion copolymerization of styrene and butyl acrylate (part 2 of this series). Surfactants are obtained in a three-step synthesis, starting from ring opening of maleic anhydride, followed by O alkylation with an aminoalkyl compound, and finishing with quaternization of the amino group in the hydrophilic part of the molecule. The chemical structure of surfactants was confirmed by 1H NMR. Melting points and critical micelle concen…

Gelchromatographie. 6. Mitt. trennungen im präparativen maßstab mit hoher auflösung

1968

Zur gelchromatographischen Trennung im Grammengen-Bereich wurde ein Recycling-Verfahren mit kontinuierlicher Einengung des Eluates entwickelt. Die Trennung von Oligomeren des Styrols, des Butylmethacrylates und des Athylenoxids unter Anwendung dieser Methode wire beschrieben. Vorteile und Grenzen des Verfahrens werden diskutiert. A recycling technic with continuous concentration of the eluate has been developed for gel chromatographic separation in the gram-scale. The separation of oligomers of styrene, butyl methacrylate and ethylene oxide by use of this method is described. Advantages and limitation of this procedure are discussed.

Preservation of dendritic cell function upon labeling with amino functionalized polymeric nanoparticles.

2010

Dendritic cells (DCs) are key players in eliciting immunity against antigens, therefore making them the focus of many investigations on immune responses in infections, cancer and autoimmune diseases. Nanosized materials have just recently been investigated for their use as carriers of antigens and as labeling agents for DCs. For this later use nanoparticles should be non-toxic and should most importantly not alter the physiological functions of DCs. Here we demonstrate that by the use of polymeric fluorescent nanoparticles as synthesized by the miniemulsion process immature DCs (iDCs) can be efficiently labeled intracellularly. Amino functionalized nanoparticles are more effective than carb…

Functionalized Polystyrene Nanoparticles Trigger Human Dendritic Cell Maturation Resulting in Enhanced CD4+T Cell Activation

2012

Nanoparticles (NP) represent a promising tool for biomedical applications. Here, sulfonate- and phosphonate-functionalized polystyrene NP are analyzed for their interaction with human monocyte-derived dendritic cells (DC). Immature dendritic cells (iDC) display a higher time- and dose-dependent uptake of functionalized polystyrene NP compared to mature dendritic cells (mDC). Notably, NP induce an enhanced maturation of iDC but not of mDC (upregulation of stimulatory molecules and cytokines). NP-triggered maturation results in a significantly enhanced T cell stimulatory capacity (increased CD4(+) T cell proliferation and IFN-γ production), indicating a shift to a pronounced Th1 response. Imm…