scholarly journals Thermoresponsive zwitterionic poly(phosphobetaine) microgels: Effect of macro‐RAFT chain length and cross‐linker molecular weight on their antifouling properties

2021 ◽  
Author(s):  
Pabitra Saha ◽  
Anand Raj Palanisamy ◽  
Marta Santi ◽  
Ritabrata Ganguly ◽  
Somashree Mondal ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Cross Linker

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

The Kinetics of Free-Radical Polymerization: Fundamental Aspects

2002 ◽  
Vol 55 (7) ◽  
pp. 399 ◽  
Author(s):  
G. T. Russell
Keyword(s):  
Molecular Weight ◽  
Steady State ◽  
Free Radical ◽  
Radical Polymerization ◽  
Chain Length ◽  
Free Radical Polymerization ◽  
Length Dependence ◽  
Model Independent ◽  
Living Free Radical Polymerization ◽  
Kinetics Of

Some fundamental aspects of the kinetics of free-radical polymerization are reviewed. So-called classical results for rate and molecular-weight distribution are first of all presented. It is shown how this approach can be built upon when chain-length-dependent termination is allowed, which it always should be. Various termination models are considered, and it is illustrated that although the models are different, rather remarkably they give common, model-independent behaviour. Some leading experimental results regarding the chain-length dependence of termination are summarized, before the chain-length dependence of other reactivities, the variation of reactivities with conversion, and non-steady state experiments are briefly discussed. Finally, living free-radical polymerization as effected by a reversible termination agent is considered. An outline of the kinetics of these systems is given, with the oft-neglected importance of conventional termination being stressed.

scholarly journals The multiple complexes formed by the interaction of platelet factor 4 with heparin

1980 ◽  
Vol 191 (3) ◽  
pp. 769-776 ◽  
Author(s):  
P E Bock ◽  
M Luscombe ◽  
S E Marshall ◽  
D S Pepper ◽  
J J Holbrook
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Chain Length ◽  
Salt Concentration ◽  
Human Platelet ◽  
Platelet Factor 4 ◽  
High Protein ◽  
Platelet Factor ◽  
The Stability ◽  
Very High

The anisotropy of the fluorescence of dansyl (5-dimethylaminonaphthalene-1- sulphonyl) groups covalently attached to human platelet factor 4 was used to detect the macromolecular compounds formed when the factor was mixed with heparin. At low heparin/protein ratios a very-high-molecular-weight compound (1) was formed that dissociated to give a smaller compound (2) when excess heparin was added. 2. A large complex was also detected as a precipitate that formed at high protein concentrations in chloride buffer. It contained 15.7% (w/w) polysaccharide, equivalent to four or five heparin tetrasaccharide units per protein tetramer. In this complex, more than one molecule of protein binds to each heparin molecule of molecular weight greater than about 6 × 10(3).3. The stability of these complexes varied with pH, salt concentration and the chain length of the heparin. The limit complexes found in excess of the larger heparins consisted of only one heparin molecule per protein tetramer, and the failure to observe complexes with four heparin molecules/protein tetramer is discussed.

A COMPARISON OF THE BINDING OF ANTITHROMBIN III AND HEPARIN COFACTOR II TO HEPARINS, NATURALLY OCCURRING GLYCOSAMINOGLYCANS AND OTHER SULPHATED POLYMERS

1987 ◽  
Author(s):  
J Dawes ◽  
D S Pepper
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Antithrombin Iii ◽  
Molar Ratio ◽  
Heparin Binding ◽  
Dextran Sulphate ◽  
Heparin Cofactor Ii ◽  
Wide Range ◽  
Pentosan Polysulphate ◽  
Binding Sequence

Antithrombin III (ATIII) and heparin cofactor II (HCII) are currently thought to be the most important protein mediators of the anticoagulant and antithrombotic activities of glycosamino-glycans. A simple, quantitative method for assessing the affinity of a protein for a sulphated polymer in the liquid phase, based on competition with immobilised heparin, has been developed. Using this technique, the binding of ATIII and HCII to a wide range of glycosaminoglycans and other sulphated polymers have been compared, and the contributions to binding of size, degree of sulphation and backbone structure of the polymers analysed.In the presence of the high protein concentrations found in plasma, unfractionated heparin inhibited the binding of ATIII to immobilised heparin with a Ki of 1 x 10-6. Binding was destroyed by N-desulphation. 1 Results with a range of low molecular weight (LMW) heparins and heparan sulphates are consistent with the view that they all contain the ATIII-binding sequence, but at a lower molar ratio than heparin. Highly sulphated synthetic polymers such as dextran sulphate bound ATIII by a different mechanism, which was molecular weight-dependent.The affinity of HCII for heparins increased markedly with heparin chain length. Binding was largely, but not entirely, mediated by sulphate residues. HCII bound to heparan and dermatan sulphates with lower affinities than to heparin, and to synthetic sulphated polymers with similar or higher affinities. Pentosan polysulphate (SP54) bound HCII as effectively as did heparin. Binding of HCII to dextran sulphate was highly dependent on molecular weight. The affinity of HCII for a sulphated polymer appears to depend both on its chain length and density of sulphation.Thus the profiles of binding of ATIII and HCII to glycosaminoglycans and other sulphated polymers are quite different. This technique is useful both for investigating the interactions of existing therapeutic anticoagulants and assessing new products.

Kinetics of the pyrolysis of propylene. Part I

1970 ◽  
Vol 48 (2) ◽  
pp. 317-325 ◽  
Author(s):  
M. Simon ◽  
M. H. Back
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Sharp Increase ◽  
Pressure Range ◽  
Pressure Change ◽  
Short Chain ◽  
Short Chain Length ◽  
Radical Process ◽  
Initiation Step ◽  
Kinetics Of

The kinetics of the pyrolysis of propylene have been studied over the temperature range 743–873 °K and the pressure range 200–600 Torr. At the lower temperatures initial rates of formation of methane, propane, and C6 products were measured and shown to be formed by a radical process of very short chain length. The orders and activation energies of the rates were consistent with the occurrence of the bimolecular initiation step[Formula: see text]Measurement of the pressure change showed that products of molecular weight higher than C7 and not measured by the analysis were formed in the initial stages of the reaction at the lower temperatures. As these higher molecular weight compounds, which are more unstable than propylene, accumulated in the system their dissociation increased the concentration of radicals and caused a sharp increase in the rates of formation of the lower molecular weight stable products.

scholarly journals Protein Engineering of Wzc To Generate New Emulsan Analogs

2007 ◽  
Vol 73 (12) ◽  
pp. 4020-4028 ◽  
Author(s):  
Hanna Dams-Kozlowska ◽  
David L. Kaplan
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Genetic Manipulation ◽  
Polyacrylamide Gel Electrophoresis ◽  
Protein A ◽  
Sodium Dodecyl ◽  
Point Mutations ◽  
Biological Properties ◽  
Feeding Strategies ◽  
Exogenous Fatty Acid

ABSTRACT Acinetobacter venetianus Rag1 produces an extracellular, polymeric lipoheteropolysaccharide termed apoemulsan. This polymer is putatively produced via a Wzy-dependent pathway. According to this model, the length of the polymer is regulated by polysaccharide-copolymerase (PCP) protein. A highly conserved proline and glycine motif was identified in all members of the PCP family of proteins and is involved in regulation of polymer chain length. In order to control the structure of apoemulsan, defined point mutations in the proline-glycine-rich region of the apoemulsan PCP protein (Wzc) were introduced. Modified wzc variants were introduced into the Rag1 genome via homologous recombination. Stable chromosomal mutants were confirmed by Southern blot analysis. The molecular weight of the polymer was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Five of the eight point mutants produced polymers having molecular weights higher than the molecular weight of the polymer produced by the wild type. Moreover, four of these five polymers had modified biological properties. Replacement of arginine by leucine (R418L) resulted in the most significant change in the molecular weight of the polymer. The R418L mutant was the most hydrophilic mutant, exhibiting decreased adherence to polystyrene, and inhibited biofilm formation. The results described in this report show the functional effect of Wzc modification on the molecular weight of a high-molecular-weight polysaccharide. Moreover, in the present study we developed a genetic system to control polymerization of apoemulsan. The use of selective exogenous fatty acid feeding strategies, as well as genetic manipulation of sugar backbone chain length, is a promising new approach for bioengineering emulsan analogs.

Engineering of Stable Recombinant Bacteria for Production of Chiral Medium-Chain-Length Poly-3-Hydroxyalkanoates

1999 ◽  
Vol 65 (8) ◽  
pp. 3265-3271 ◽  
Author(s):  
Maria A. Prieto ◽  
Michele B. Kellerhals ◽  
Gian B. Bozzato ◽  
Dragan Radnovic ◽  
Bernard Witholt ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Expression System ◽  
Average Molecular Weight ◽  
Polydispersity Index ◽  
Recombinant Bacteria ◽  
E Coli ◽  
Medium Chain ◽  
Medium Chain Length ◽  
Pha Production

ABSTRACT In order to scale up medium-chain-length polyhydroxyalkanoate (mcl-PHA) production in recombinant microorganisms, we generated and investigated different recombinant bacteria containing a stable regulated expression system for phaC1, which encodes one of the mcl-PHA polymerases of Pseudomonas oleovorans. We used the mini-Tn5 system as a tool to constructEscherichia coli 193MC1 and P. oleovoransPOMC1, which had stable antibiotic resistance and PHA production phenotypes when they were cultured in a bioreactor in the absence of antibiotic selection. The molecular weight and the polydispersity index of the polymer varied, depending on the inducer level. E. coli 193MC1 produced considerably shorter polyesters thanP. oleovorans produced; the weight average molecular weight ranged from 67,000 to 70,000, and the polydispersity index was 2.7. Lower amounts of inducer added to the media shifted the molecular weight to a higher value and resulted in a broader molecular mass distribution. In addition, we found that E. coli 193MC1 incorporated exclusively the R configuration of the 3-hydroxyoctanoate monomer into the polymer, which corroborated the enantioselectivity of the PhaC1 polymerase enzyme.

scholarly journals Impacts of cross-linker chain length on the physical properties of polyampholyte hydrogels

2019 ◽  
Vol 14 (3) ◽  
pp. 031002 ◽  
Author(s):  
Emily Mariner ◽  
Stephanie L. Haag ◽  
Matthew T. Bernards
Keyword(s):  
Physical Properties ◽  
Chain Length ◽  
Linker Chain ◽  
Cross Linker

Determination of Mark-Houwink Parameters and Absolute Molecular Weight of Medium-Chain-Length Poly(3-Hydroxyalkanoates)

2012 ◽  
Vol 21 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Manoj Nerkar ◽  
Juliana A. Ramsay ◽  
Bruce A. Ramsay ◽  
Marianna Kontopoulou ◽  
Robin A. Hutchinson
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Medium Chain ◽  
Medium Chain Length
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