scholarly journals Alkylation of Aromatic Compounds with Pentabromobenzyl Bromide and Tetrabromoxylene Dibromide as a New Route to High Molecular Weight Brominated Flame Retardants

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 352
Author(s):  
Mark Gelmont ◽  
Michael Yuzefovitch ◽  
David Yoffe ◽  
Eyal Eden ◽  
Sergei Levchik
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Flame Retardants ◽  
Brominated Flame Retardants ◽  
High Thermal Stability ◽  
Aromatic Molecules ◽  
Sustainable Products ◽  
Aromatic Polymers ◽  
International Human ◽  
Better Than

In the view of many national and international human health and environmental regulations, polymeric flame retardants are sustainable products. In this work, a series of high molecular weight and polymeric brominated flame retardants are synthesized by the alkylation of aromatic molecules or the alkylation of aromatic polymers with pentabromobenzyl bromide (PBBB) or tetrabromoxylylene dibromide (TBXDB). The flame retardants prepared via the alkylation of toluene or diphenylethane with PBBB were found to be not truly polymeric but had high Mw > 1400. However, the alkylation of the same aromatic molecules by a mixture of PBBB and TBXDP resulted in polymeric flame retardants with Mw > 130,000. Two other polymeric flame retardants were prepared by the alkylation of aromatic polymers (polyphenylene ether or polystyrene) with PBBB. It was found that the new flame retardants had a high bromine content of more than 68%. They showed high thermal stability with the onset of thermal decomposition above 360 °C and a maximum rate of weight loss at about 375–410 °C. The newly synthesized flame retardants were tested in different thermoplastics. Flame retardant efficiency and physical properties were comparable or better than the reference commercial flame retardants.

The Equation of State and the Temperature, Pressure, and Shear Dependence of Viscosity for a Highly Viscous Reference Liquid, Dipentaerythritol Hexaisononanoate

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Scott Bair ◽  
Tsuyoshi Yamaguchi
Keyword(s):  
Molecular Weight ◽  
Shear Stress ◽  
Equation Of State ◽  
High Molecular Weight ◽  
Free Volume ◽  
Newtonian Limit ◽  
Scaling Models ◽  
The Difference ◽  
Better Than ◽  
Low Shear

Measurements are reported for dipentaerythritol hexaisononanoate (DiPEiC9) of pressure–volume–temperature (pVT) response to pressures to 400 MPa and temperatures to 100 °C, and of viscosity at pressures to 700 MPa and temperatures to 90 °C and shear stress to 18 MPa. These data complement the low-shear viscosities published by Harris to pressures to 200 MPa and the compressions by Fandiño et al. to 70 MPa. The improved Yasutomi correlation reproduces all viscosity measurements with accuracy better than the Doolittle free volume and the Bair and Casalini thermodynamic scaling models which require an equation of state (EoS). The interaction parameter for thermodynamic scaling, γ = 3.6, is less than that reported by Harris (γ = 4.2) and the difference is primarily in the choice of EoS. The shear stress at the Newtonian limit, about 6 MPa, is exceptionally large given the high molecular weight of DiPEiC9. The large Newtonian limit is also seen in the oscillatory shear response.

scholarly journals Glycol-functionalized ionic liquids for high-temperature enzymatic ring-opening polymerization

RSC Advances ◽  
2018 ◽  
Vol 8 (63) ◽  
pp. 36025-36033 ◽  
Author(s):  
Hua Zhao ◽  
Lennox O. Afriyie ◽  
Nathaniel E. Larm ◽  
Gary A. Baker
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Ionic Liquids ◽  
High Temperature ◽  
High Molecular Weight ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
High Thermal Stability ◽  
Polymerization Reaction

New glycol-functionalized ionic liquids exhibit high thermal stability and are lipase-compatible, leading to a high molecular weight of polyester in the enzymatic ring-opening polymerization reaction.

Polymerization of disubstituted acetylenes by monodentate NHC-Pd catalysts

2015 ◽  
Vol 6 (40) ◽  
pp. 7127-7132 ◽  
Author(s):  
Min Li ◽  
Changle Chen
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
High Thermal Stability ◽  
Pd Catalysts

Monodentate NHC-Pd catalyzed efficient polymerization of disubstituted acetylenes to generate polymers with high molecular weight and high thermal stability.

Carbon Membranes: A Viable Technology for the Recovery and Purification of Hydrogen Gas

2006 ◽  
Vol 971 ◽  
Author(s):  
Anna Merritt ◽  
Ramakrishnan Rajagopalan ◽  
Henry C Foley
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Hydrogen Gas ◽  
Carbon Membranes ◽  
Polyfurfuryl Alcohol ◽  
Porous Stainless Steel ◽  
Precursor Material ◽  
Binary Separations ◽  
Asymmetric Carbon ◽  
Better Than

ABSTRACTHigh throughput, asymmetric carbon membranes derived from pyrolysis of polyfurfuryl alcohol (PFA) have been fabricated on a novel support composed of porous stainless steel filled with nanoparticles. Variation of PFA molecular weight was found to have a significant impact on the single gas permeances of the resultant carbon membranes. High molecular weight precursor material yielded the best results; oxygen permeance values for membranes synthesized from high molecular weight resins were on the order of ∼1×10−8 mol m−2s−1Pa−1 with oxygen over nitrogen ideal selectivities greater than 7. Binary separations of hydrogen from nitrogen and hydrogen from carbon monoxide were carried out using a NPC membrane synthesized from high molecular weight precursor material. For both separations, hydrogen purities of better than 99% by volume were obtained in the permeate stream.

scholarly journals Hyaluronic Acid as an Alternative to Autologous Human Serum Eye Drops: Initial Clinical Results with High-Molecular-Weight Hyaluronic Acid Eye Drops

2019 ◽  
Vol 10 (2) ◽  
pp. 244-255 ◽  
Author(s):  
Ria Beck ◽  
Oliver Stachs ◽  
Anita Koschmieder ◽  
Wolfgang G.K. Mueller-Lierheim ◽  
Sabine Peschel ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hyaluronic Acid ◽  
High Molecular Weight ◽  
Dry Eye ◽  
Autologous Serum ◽  
Control Group ◽  
Eye Drops ◽  
Very High ◽  
Serum Eye Drops ◽  
Better Than

Introduction: Autologous serum eye drops (ASED) are used in the treatment of most severe stages of dry eye. Once introduced, it is currently considered impossible to return to other lubricating eye drops or other commercially available therapeutic regimen. Materials and Methods: In a randomized study, non-preserved high-molecular-weight hyaluronic acid eye drops were offered as an alternative to 11 patients using autologous serum treatment for at least 3 months. The control group (n = 5) continued their treatment with ASED. The verum group (n = 6) used very-high-molecular-weight hyaluronic eye drops (Comfort Shield®) instead of the ASED. Results: From four of initially six patients in the verum group that finished the study, 2 (50%) preferred to stay with the very-high-molecular-weight hyaluronic acid eye drops beyond the trial period, the other two returned to the earlier therapy with ASED. The control group continued their treatment as before and finished the study after 8 weeks. Conclusion: For the first time, artificial eye drops, i.e., high-molecular-weight hyaluronic acid eye drops, offered an acceptable alternative to ASED. Some patients perceived these drops as even better than the patient’s own serum. This is the first evidence that optimization of the molecular structure of hyaluronic acid can be used to create eye drops that are perceived to be better than other tested tear substitutes and even patients’ own serum. This offers a new treatment perspective for patients with very severe dry eye disease.

Reconstruction of Two-Dimensional Projections of GP 32*I

1981 ◽  
Vol 39 ◽  
pp. 38-39
Author(s):  
H.A. Cohen ◽  
W. Chiu ◽  
J. Hosoda
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Uranyl Acetate ◽  
Distilled Water ◽  
Acetate Solution ◽  
Two Dimensional ◽  
Parent Molecule ◽  
T4 Bacteriophage ◽  
Electron Imaging ◽  
Better Than

GP 32 (molecular weight 35000) is a T4 bacteriophage protein that destabilizes the DNA helix. The fragment GP32*I (77% of the total weight), which destabilizes helices better than does the parent molecule, crystallizes as platelets thin enough for electron diffraction and electron imaging. In this paper we discuss the structure of this protein as revealed in images reconstructed from stained and unstained crystals.Crystals were prepared as previously described. Crystals for electron microscopy were pelleted from the buffer suspension, washed in distilled water, and resuspended in 1% glucose. Two lambda droplets were placed on grids over freshly evaporated carbon, allowed to sit for five minutes, and then were drained. Stained crystals were prepared the same way, except that prior to draining the droplet, two lambda of aqueous 1% uranyl acetate solution were applied for 20 seconds. Micrographs were produced using less than 2 e/Å2 for unstained crystals or less than 8 e/Å2 for stained crystals.

Microtubule motors and other maps

1990 ◽  
Vol 48 (3) ◽  
pp. 1-1
Author(s):  
Richard B. Vallee
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Cytoplasmic Dynein ◽  
Organelle Transport ◽  
Structural Components ◽  
Microtubule Associated Proteins ◽  
Microtubule Motors ◽  
Associated Proteins ◽  
The Subject ◽  
Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

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