scholarly journals Synthesis of High cis-Polybutadiene in Styrene Solution with Neodymium-Based Catalysts: Towards the Preparation of HIPS and ABS via In Situ Bulk Polymerization

2016 ◽  
Vol 2016 ◽  
pp. 1-11
Author(s):  
Ramón Díaz de León ◽  
Florentino Soriano Corral ◽  
Francisco Javier Enríquez-Medrano ◽  
Gabriela Bosques Ibarra ◽  
Patricia de León Martínez ◽  
...  
Keyword(s):  
Catalyst System ◽  
Bulk Polymerization ◽  
Activation Process ◽  
Morphological Development ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Butadiene Polymerization ◽  
Melting Endotherm ◽  
Synthesized Materials

In a first step, 1,3-butadiene was selectively polymerized at 60°C in styrene as solvent using NdV3/DIBAH/EASC as the catalyst system. The catalyst system activation process, the addition order of monomers and catalyst components, and the molar ratios [Al]/[Nd] and [Cl]/[Nd] were studied. The catalyst system allowed the selective 1,3-butadiene polymerization, reaching conversions between 57.5 and 88.1% with low polystyrene contents in the order of 6.3 to 15.4%. Molecular weights ranging from 39,000 to 150,000 g/mol were obtained, while cis-1,4 content was found in the interval of 94.4 to 96.4%. On the other hand, the glass transition temperatures of synthesized materials were established in the range of −101.9 to −107.4°C, explained by the presence of polystyrene segments in the polybutadiene chains; in the same sense, the polybutadienes did not show the typical melting endotherm of high cis-polybutadienes. In a second step, the resulting styrene/high cis-1,4 polybutadiene solutions were used to synthesize ABS (adding a fraction of acrylonitrile monomer) and HIPS via in situ bulk polymerizations and the results were discussed in terms of morphological development, molecular parameters, dynamical mechanical behavior, and mechanical properties.

Synthesis of polypropylene with varied microstructure and molecular weights characteristics using supported titanium catalyst system

2010 ◽  
Vol 18 (2) ◽  
pp. 235-239 ◽  
Author(s):  
Priyanshu B. Vyas ◽  
Sukhdeep Kaur ◽  
Harshad R. Patil ◽  
Virendra K. Gupta
Keyword(s):  
Catalyst System ◽  
Titanium Catalyst ◽  
Molecular Weights

Butadiene polymerization over a π-allylnickel-alumina-silica gel catalyst system

1980 ◽  
Vol 13 (4) ◽  
pp. 319-322 ◽  
Author(s):  
W. Skupiński ◽  
M. Zawartke ◽  
St. Malinowski
Keyword(s):  
Silica Gel ◽  
Catalyst System ◽  
Butadiene Polymerization

The disorderly exfoliated LDHs/PMMA nanocomposite synthesized by in situ bulk polymerization

Polymer ◽  
2005 ◽  
Vol 46 (14) ◽  
pp. 5065-5074 ◽  
Author(s):  
Guo-An Wang ◽  
Cheng-Chien Wang ◽  
Chuh-Yung Chen
Keyword(s):  
Bulk Polymerization

scholarly journals The macromolecular properties of blood-group-specific glycoproteins. Characterization of a series of fractions obtained by density-gradient ultracentrifugation

1974 ◽  
Vol 143 (3) ◽  
pp. 669-679 ◽  
Author(s):  
K. Ramakrishnan Bhaskar ◽  
J. Michael Creeth
Keyword(s):  
Density Gradient ◽  
Blood Group ◽  
Buoyant Density ◽  
Physicochemical Characterization ◽  
Cyst Fluid ◽  
Equilibrium Density ◽  
Density Gradient Ultracentrifugation ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Blood Group Substances

1. Equilibrium density-gradient ultracentrifugation in caesium salts was used in two stages in the isolation and subfractionation of the glycoprotein component from a human ovarian-cyst fluid. The eight main subfractions thus obtained were the subject of detailed physicochemical characterization. 2. The fractions were unimodal in buoyant-density distribution, but had discrete ρ0 values ranging from 1.31 to 1.35. 3. Weight-average molecular weights and sedimentation coefficients decreased regularly with decreasing density of the fraction, whereas the partial specific volumes and selective solvation parameters increased. The latter behaviour correlates well with the increasing peptide content of the lighter fractions. 4. The fractions exhibited a range of analytical composition, although all were within the limits previously observed for blood-group substances of Lea specificity. All fractions had approximately equal Lea activity. The peptide content varied systematically from 7% for the densest fraction to 15% for the lightest, but the relative distributions of the amino acids remained essentially constant throughout the series. In particular, serine plus threonine plus proline made up about 50% of the peptide content of all the fractions. Fucose, galactose and N-acetylglucosamine contents decreased with increasing peptide content of the fractions, but N-acetylgalactosamine and sialic acid exhibited the opposite trend. Molar ratios of N-acetylgalactosamine to the sum of serine and threonine remained essentially constant at 0.8–0.9, implying a high degree of glycosylation of all the molecules, but the ratio of N-acetylglucosamine to N-acetylgalactosamine decreased steadily with increasing peptide content, suggesting the presence of oligosaccharide side chains of various lengths. The results are discussed in terms of the accepted structure of glycoprotein molecules. 5. Experiments on the glycoproteins extracted with phenol from the same cyst fluid have confirmed that equilibrium centrifugation in caesium salts does not remove any non-covalently bound protein nor cause any changes in the tertiary structures of these glycoprotein molecules.

Nanoclay-reinforced Polyacrylamide Composite: Synthesis, Structural and Mechanical Characterization

2009 ◽  
Vol 1239 ◽  
Author(s):  
Yong Sun ◽  
Zaiwang Huang ◽  
Xiaodong Li
Keyword(s):  
Thin Films ◽  
Deformation Behavior ◽  
Mechanical Characterization ◽  
Interfacial Strength ◽  
Localized Deformation ◽  
Nano Indentation ◽  
Atomic Force ◽  
Nanocomposite Thin Films ◽  
Synthesized Materials

AbstractA facile electrophoretic deposition method was successfully applied to achieve novel nanoclay-reinforced polyacrylamide nanocomposite thin films. A special curled architecture of the re-aggregated nanoclay-platelets was identified, providing a possible source for realizing the interlocking mechanism in the nanocomposites. The curled architecture could be the result from strain releasing when the thin films were peeled off from the substrates. Through micro-/nano-indentation and in situ observation of the deformation during tensile test with an atomic force microscope (AFM), the localized deformation mechanism of the synthesized materials was investigated in further details. The results implied that a localized crack diversion mechanism worked in the synthesized nanocomposite thin films, which resembled its nature counterpart-nacre. The deformation behavior and fracture mechanism were discussed with reference to lamellar structure, interfacial strength between the nanoclays and the polyacrylamide matrix, and nanoclay agglomeration.

Polymerization of n-butyl methylacrylate using bis(β- ketoamino)nickel(II)/MAO catalytic systems

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Xiaohui He ◽  
Yiwang Chen ◽  
Yongming Liu ◽  
Muqing Chen ◽  
Shuxian Yu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Monomer Concentration ◽  
Polymerization Temperature ◽  
Moderate Activity ◽  
Polymerization Time ◽  
Catalytic Systems ◽  
Molecular Weights ◽  
Molar Ratios ◽  
Broad Molecular Weight Distribution ◽  
C Nmr

AbstractThe polymerizations of n-butyl methylacrylate (nBMA) were carried out using bis(β-ketoamino)nickel(II) complexes (Ni[CH3C(O)CHC(NR)CH3]2: R = phenyl, 1; R = naphthyl, 2) in combination with methylaluminoxane (MAO) in toluene. The effect of parameters such as polymerization temperature, Al/Ni molar ratios, polymerization time, and monomer concentration, on catalytic polymerization activity and polymer molecular weights, were examined in detail. Both of the nickel(II) catalytic systems exhibited moderate activity, and produced P(nBMA) with high molecular weight and relatively broad molecular weight distribution (Mw/Mn=2.0~3.0. The obtained polymer has been characterized by means of FTIR, 1H NMR, 13C NMR, DSC, and WAXD technique and was confirmed to be syndio-rich stereospecific P(nBMA).

scholarly journals Investigation of Silicon Nanoparticle-Polystyrene Hybrids

2019 ◽  
Vol 2 (2) ◽  
pp. 49-50
Author(s):  
Madihah Khan ◽  
Alyxandra Thiessen ◽  
I Teng Cheong ◽  
Sarah Milliken ◽  
Jonathan G. C. Veinot
Keyword(s):  
Silicon Nanoparticles ◽  
In Situ Polymerization ◽  
Toxic Substance ◽  
Homogeneous Mixture ◽  
Silicon Nanoparticle ◽  
Molecular Weights ◽  
Abundant Element ◽  
The Stability ◽  
Led Lights

Current LED lights are created with quantum dots made of metals like selenium, tellurium, and cadmium which can be toxic. Silicon is used as a non-toxic substance and is the second most abundant element in the earth's crust. When silicon is prepared at a nanometer size, unique luminesce optical properties emerge that can be tuned using sized surface chemistry. Therefore, silicon nanoparticles can be used as an alternative emitter for LED lights. To produce hydride-terminated silicon nanoparticles we must synthesize the particles. Hydrogen silsesquioxane (HSQ) is processed at 1100 °C for one hour causing Si to cluster and form a SiO2 matrix, also known as the composite. The composite is then manually crushed in ethanol. The solution is further ground using glass beads, then filtered to get the composite powder. The final step is the HF etching. The hydride-terminated particles are then functionalized using three different methods to synthesize silicon nanoparticle-polystyrene hybrids, which determine the magnitude of luminosity and the quality of the hybrids. We spin coat each method and results were analyzed. Method 1 uses heat to functionalize hydride-terminated silicon nanoparticles with styrene. This process also causes styrene to attach to styrene to form a polystyrene chain. Method 1 gave a homogeneous mixture which yielded a consistent, bright and homogenous film. In method 2, dodecyl-terminated silicon nanoparticles are mixed with premade polystyrene. While this method gave better control of the amount of silicon nanoparticles inside the polymer hybrid, a homogeneous mixture was not created due to the different structures of polystyrene and dodecyl chains. Method 3 has dodecyl-terminated silicon with in-situ styrene polymerization. It generated a homogeneous mixture. The in-situ polymerization stabilizes the particles, allowing for brighter luminescence. Because of the stability and lower molecular weight, the mixture was easier to dissolve. We concluded that the different methods resulted in different polymer molecular weights and this created distinct properties between the polymer hybrids when spin-coating.    

In Situ Study of The Exposure of Polycarbonate to an Argon Plasma

1995 ◽  
Vol 385 ◽  
Author(s):  
S. Vallon ◽  
B. Drevillon ◽  
F. Poncin-Epaillard ◽  
J. C. Rostaing
Keyword(s):  
Structural Changes ◽  
Argon Plasma ◽  
Silica Layer ◽  
Molecular Weights ◽  
In Situ Study ◽  
Polar Groups ◽  
Unit Scale ◽  
Two Populations ◽  
Polymer Unit

ABSTRACTThe exposure of polycarbonate to an argon plasma is studied using in situ ellipsometry from the UV to the IR, nuclear magnetic resonance and light scattering measurements. An increase in the refractive index and the existence of two populations of different molecular weights show that structural changes occur in the polymer. They are correlated with modifications at the polymer unit scale, such as formation of new polar groups and decrease in dimethyl groups. Two simultaneous reaction mechanisms must be considered to account for these changes. The adhesion of a silica layer on treated polycarbonate is then discussed.

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