scholarly journals Synthetic Approaches for Poly(Phenylene) Block Copolymers via Nickel Coupling Reaction for Fuel Cell Applications

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1614 ◽  
Author(s):  
Adam F. Nugraha ◽  
Songmi Kim ◽  
Farid Wijaya ◽  
Byungchan Bae ◽  
Dongwon Shin
Keyword(s):  
Block Copolymers ◽  
Cost Savings ◽  
Coupling Reaction ◽  
Chloride Ion ◽  
Gel Permeation Chromatography ◽  
Nickel Catalysts ◽  
Degree Of Polymerization ◽  
Random Copolymers ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer

Several methods to synthesize poly(phenylene) block copolymers through the nickel coupling reaction were attempted to reduce the use of expensive nickel catalysts in polymerization. The model reaction for poly(phenylene) having different types of dichlorobenzene derivative monomers illustrated the potential use of cost-effective catalysts, such as NiBr2 and NiCl2, as alternatives to more expensive catalysts (e.g., bis(1,5-cyclooctadiene)nickel(0) (Ni(COD)2)). By catalyzing the polymerization of multi-block poly(phenylene) with NiBr2 and NiCl2, random copolymers with similar molecular weights could be prepared. However, these catalysts did not result in a high-molecular-weight polymer, limiting their wide scale application. Further, the amount of Ni(COD)2 could be reduced in this study by approximately 50% to synthesize poly(phenylene) multi-block copolymers, representing significant cost savings. Gel permeation chromatography and nuclear magnetic resonance results showed that the degree of polymerization and ion exchange capacity of the copolymers were almost the same as those achieved through conventional polymerization using 2.5 times as much Ni(COD)2. The flexible quaternized membrane showed higher chloride ion conductivity than commercial Fumatech membranes with comparable water uptake and promising chemical stability.

scholarly journals Hydrolytic Degradation of Comb-Like Graft Poly (Lactide-co-Trimethylene Carbonate): The Role of Comonomer Compositions and Sequences

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2024
Author(s):  
Xuefei Leng ◽  
Wenwen Zhang ◽  
Yiying Wang ◽  
Yanshai Wang ◽  
Xiaoqing Li ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Hydrolytic Degradation ◽  
Gel Permeation Chromatography ◽  
Random Copolymers ◽  
Degradation Behavior ◽  
Weight Retention ◽  
Trimethylene Carbonate ◽  
Degradation Rates ◽  
Degradation Behaviors ◽  
Property Changes

The effect of sequence on copolymer properties is rarely studied, especially the degradation behavior of the biomaterials. A series of linear-comb block, gradient, random copolymers were successfully achieved using hydroxylated polybutadiene as the macroinitiator by simple ring-opening polymerization of l-lactide (l-LA) and 1,3-trimethylene carbonate (TMC). The hydrolytic degradation behaviors of the copolymers were systemically evaluated by using nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM) to illustrate the influences of comonomer compositions and sequence structures. The linear-comb block copolymers (lcP(TMC-b-LLA)) with different compositions had different degradation rates, which increased with l-LA content. Thermal property changes were observed with decreased Tm and increased ΔHm in all block copolymers during the degradation. To combine different sequence structures, unique degradation behaviors were observed for the linear-comb block, gradient and random copolymers even with similar comonomer composition. The degradation rates of linear-comb PLLA-gradient-PTMC (lcP(LLA-grad-TMC)) and linear-comb PLLA-random-PTMC (lcP(LLA-ran-TMC)) were accelerated due to the loss of regularity and crystallinity, resulting in a remarkable decrease on weight retention and molar mass. The hydrolysis degradation rate increased in the order lcP(TMC-b-LLA), lcP(LLA-ran-TMC), lcP(LLA-grad-TMC). Therefore, the hydrolytic degradation behavior of comb-like graft copolymers depends on both the compositions and the sequences dramatically.

The Relationship Between Molecular Structure and Spectroscopic Properties of a Series of Transition Metal-Containing Phenylacetylene Oligomers and Polymers

2001 ◽  
Vol 665 ◽  
Author(s):  
Thomas M. Cooper ◽  
Daniel G McLean ◽  
Joy E. Rogers
Keyword(s):  
Molecular Weight ◽  
Transition Metal ◽  
Flash Photolysis ◽  
Monomer Unit ◽  
Spectroscopic Properties ◽  
Degree Of Polymerization ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Transition Energies ◽  
The Relationship

ABSTRACTTo develop novel nonlinear dyes for photonic applications, we synthesized a series of transition metal-containing phenylacetylene oligomers and polymers. The optical properties of these compounds were measured by UV/Vis, fluorescence, and flash photolysis experiments. As the number of oligomer units increased, the transition energies decreased. A solvatochromism experiment suggested the fluorescing state was different from the absorbing state. As a group, the spectra of the polymeric versions of these complexes were red shifted from the spectra of the oligomers. The polymeric complexes had less clear trends relating the number of oligomer units to transition energies. A comparison of a low molecular weight and a high molecular weight polymer showed the degree of polymerization caused spectroscopic shifts comparable to the number of phenylacetylene units in the monomer unit.

Redox-active polymer-nanoparticle hybrid materials

2000 ◽  
Vol 72 (1-2) ◽  
pp. 67-72 ◽  
Author(s):  
Keith J. Watson ◽  
Jin Zhu ◽  
SonBinh T. Nguyen ◽  
Chad A. Mirkin
Keyword(s):  
Gold Nanoparticles ◽  
Block Copolymers ◽  
Hybrid Materials ◽  
Ring Opening ◽  
Gel Permeation Chromatography ◽  
Polymer Chains ◽  
Electrochemical Studies ◽  
Redox Active ◽  
Gel Permeation ◽  
Current Rectification

Ring-opening metathesis polymerization was used to modify organic soluble gold nanoparticles with redox-active polymers. A gel-permeation chromatography study revealed that each nanoparticle is modified with approximately 11 polymer chains. Electrochemical studies of nanoparticles modified with block copolymers of two different redox-active groups revealed that each monomer is electrochemically accessible, while no current rectification was observed.

Study of block copolymers by gel-permeation chromatography

1982 ◽  
Vol 24 (6) ◽  
pp. 1512-1517 ◽  
Author(s):  
V.V. Nesterov ◽  
V.D. Krasikov ◽  
Ye.V. Chubarova ◽  
B.G. Belen'kii
Keyword(s):  
Block Copolymers ◽  
Gel Permeation Chromatography ◽  
Gel Permeation

Intrinsic viscoelasticity in thin high-molecular-weight polymer films

2014 ◽  
Vol 89 (6) ◽  
Author(s):  
Xiaoyuan Sheng ◽  
Frédéric Wintzenrieth ◽  
Katherine R. Thomas ◽  
Ullrich Steiner
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Polymer Films ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer

scholarly journals The Food Additive Xanthan Gum Drives Adaptation of the Human Gut Microbiota

2021 ◽  
Author(s):  
Matthew P. Ostrowski ◽  
Sabina Leanti La Rosa ◽  
Benoit J. Kunath ◽  
Andrew Robertson ◽  
Gabriel Pereira ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Xanthan Gum ◽  
Enrichment Culture ◽  
Food Additives ◽  
Food Additive ◽  
Glycoside Hydrolase Family ◽  
Human Gut ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Uncultured Bacterium

SummaryThe diets of industrialized countries reflect the increasing use of processed foods, often with the introduction of novel food additives. Xanthan gum is a complex polysaccharide with unique rheological properties that have established its use as a widespread stabilizer and thickening agent1. However, little is known about its direct interaction with the gut microbiota, which plays a central role in digestion of other, chemically-distinct dietary fiber polysaccharides. Here, we show that the ability to digest xanthan gum is surprisingly common in industrialized human gut microbiomes and appears to be contingent on the activity of a single bacterium that is a member of an uncultured bacterial genus in the family Ruminococcaceae. We used a combination of enrichment culture, multi-omics, and recombinant enzyme studies to identify and characterize a complete pathway in this uncultured bacterium for the degradation of xanthan gum. Our data reveal that this keystone degrader cleaves the xanthan gum backbone with a novel glycoside hydrolase family 5 (GH5) enzyme before processing the released oligosaccharides using additional enzymes. Surprisingly, some individuals harbor a Bacteroides species that is capable of consuming oligosaccharide products generated by the keystone Ruminococcaceae or a purified form of the GH5 enzyme. This Bacteroides symbiont is equipped with its own distinct enzymatic pathway to cross-feed on xanthan gum breakdown products, which still harbor the native linkage complexity in xanthan gum, but it cannot directly degrade the high molecular weight polymer. Thus, the introduction of a common food additive into the human diet in the past 50 years has promoted the establishment of a food chain involving at least two members of different phyla of gut bacteria.

scholarly journals Activated Flooded Jets and Immiscible Layer Technology Help to Remove and Prevent the Formation of Bottom Sediments in the Oil Storage Tanks

2021 ◽  
Author(s):  
Georgii V. Nesyn
Keyword(s):  
Crude Oil ◽  
Bottom Sediments ◽  
External Heat ◽  
Storage Tanks ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Oil Storage ◽  
Screw Propeller ◽  
Fit For Purpose ◽  
Tank Bottom

Two flooded jet methods of tank bottom sediments caving based on either screw propeller generation or nozzle jets generated with entering crude head oppose each other. The comparison is not advantageous for the first one. Exceptionally if crude oil contains some concentration of high molecular weight polymer which can perform Drag Reduction. In this case, the jet range increases by many times, thus, upgrading the capability of caving system. Preventing the sedimentation of crude oil heavy components may be put into practice with Immiscible Layer Technology. Before filling the tank with crude oil, some quantity of heavy liquid, that is immiscible with all the components of crude oil, is poured into the tank. The most suitable/fit for purpose and available liquid is glycerin. Neither paraffin and resins, nor asphaltenes can penetrate through the glycerin layer to settle down at the tank bottom because of its density, which is equal to 1.26 g/cm3. Instead, sediments are concentrated at/on the glycerin surface and when it is heated in external heat exchanger all the sediments ought to move upwards with the convection streams. Thus, no deteriorate sediment is formed in the tank bottom.

scholarly journals Polymethylmethacrylate (PMMA) Encapsulated Graphene Oxide Nanocomposite: Pre-modification, Synthesis, and Latex Stability

2020 ◽  
Author(s):  
Hui Wang ◽  
Letian Wang ◽  
Shanyu Meng ◽  
Hanxue Lin ◽  
Melanie Correll ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Critical Role ◽  
Miniemulsion Polymerization ◽  
Sem Analysis ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Transmission Electron ◽  
Composite Production ◽  
Uniform Particle Size

The compatibility of graphene or graphene oxide with its dispersion medium (polymer) plays a critical role in the formation nanocomposite materials with significant property improvements. Environmentally friendly miniemulsion polymerization, which allows a formation of nanoencapsulation in an aqueous phase and high molecular weight polymer/composite production is one promising method. In this study, we screened a series of amphiphilic modifiers and found that the quaternary ammonium (ar-vinyl benzyl) trimethyl ammonium chloride (VBTAC) pending carbon double bonds could effectively modify the graphene oxide (GO) to be compatible with the organophilic monomer. After that, free radical miniemulsion polymerization could successfully synthesize stable latex of exfoliated poly (methyl methacrylate) (PMMA)/ GO nanocomposite. The final latex had an extended storage life and a relatively uniform particle size distribution. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) analysis of this latex and its films indicated successful encapsulation of exfoliated nano-dimensional graphene oxide inside a polymer matrix.

scholarly journals Synthesis of Poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) Block Copolymer by Redox Polymerization and Atom Transfer Radical Polymerization

2018 ◽  
Vol 18 (3) ◽  
pp. 537 ◽  
Author(s):  
Melahat Göktaş ◽  
Guodong Deng
Keyword(s):  
Block Copolymers ◽  
Methyl Methacrylate ◽  
Atom Transfer Radical Polymerization ◽  
Radical Polymerization ◽  
Gel Permeation Chromatography ◽  
High Yield ◽  
Resonance Spectroscopy ◽  
Atom Transfer ◽  
Poly Methyl Methacrylate ◽  
Redox Polymerization

Poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) [PMMA-b-PNIPAM] block copolymers were obtained by a combination of redox polymerization and atom transfer radical polymerization (ATRP) methods in two steps. For this purpose, PMMA macroinitator (ATRP-macroinitiator) was synthesized by redox polymerization of methyl methacrylate and 3-bromo-1-propanol using Ce(NH4)2(NO3)6 as a catalyst. The synthesis of PMMA-b-PNIPAM block copolymers was carried out by means of ATRP of ATRP-macroinitiator and NIPAM at 60 °C. The block copolymers were obtained in high yield and high molecular weight. The characterization of products was accomplished by using multi instruments and methods such as nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, and thermogravimetric analysis.

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