The influence of polyanion molecular weight on polyelectrolyte multilayers at surfaces: elasticity and susceptibility to saloplasticity of strongly dissociated synthetic polymers at fluid–fluid interfaces

2017 ◽  
Vol 19 (35) ◽  
pp. 23781-23789 ◽  
Author(s):  
Ashley D. Cramer ◽  
Wen-Fei Dong ◽  
Natalie L. Benbow ◽  
Jessie L. Webber ◽  
Marta Krasowska ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Elastic Modulus ◽  
Chain Length ◽  
Synthetic Polymers ◽  
Polyelectrolyte Multilayers ◽  
Fluid Interfaces ◽  
Polyanion Chain

Decreasing polyanion chain length increases the elastic modulus and saloplasticity threshold in freestanding polyelectrolyte multilayers.

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 Influence of Molecular Weight on the Orientation and Properties of Polymethyl Methacrylate Sheets

2018 ◽  
Vol 45 (2) ◽  
pp. 47-51
Author(s):  
I.D. Simonov-Emel'yanov ◽  
K.V. Shirshin ◽  
P.V. Motsinov ◽  
S.V. Vlasov
Keyword(s):  
Molecular Weight ◽  
Elastic Modulus ◽  
Polymethyl Methacrylate ◽  
Considerable Increase ◽  
Deformation Characteristics ◽  
Physicomechanical Characteristics

The influence of molecular weight on the process of orientation stretching and the combination of physicomechanical characteristics of specimens of polymethyl methacrylate (PMMA) is examined. Orientation stretching and increase in the molecular weight of PMMA from 0.52 to 4.6 × 106 g/mol lead to a considerable increase in strength and elastic modulus (σt by a factor of 2.6, E by a factor of 2.5). It is established that the deformation characteristics of oriented PMMA specimens increase by a factor of 10 when the molecular weight is increased from 0.52 to 4.6 × 106 g/mol, which opens up new possibilities in the processing of sheets and films of PMMA.

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.

PEG Cross-Linked Alginate Hydrogels with Controlled Mechanical Properties

1998 ◽  
Vol 530 ◽  
Author(s):  
Petra Eiselt ◽  
Jon A. Rowley ◽  
David J. Mooney
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Molecular Weight ◽  
Elastic Modulus ◽  
Cell Transplantation ◽  
Cross Linking ◽  
Cross Link ◽  
Link Density ◽  
A Cell ◽  
Cross Link Density

AbstractReconstruction of tissues and organs utilizing cell transplantation offers an attractive approach for the treatment of patients suffering from organ failure or loss. Highly porous synthetic materials are often used to mimic the function of the extracellular matrix (ECM) in tissue engineering, and serve as a cell delivery vehicle for the formation of tissues in vivo. Alginate, a linear copolysaccharide composed of D-mannuronic acid (M) and L-guluronic acid (G) units is widely used as a cell transplantation matrix. Alginate is considered to be biocompatible, and hydrogels are formed in the presence of divalent cations such as Ca2+, Ba2+ and Sr2+. However, ionically cross-linked alginate gels continuously lose their mechanical properties over time with uncontrollable degradation behavior. We have modified alginate via covalent coupling of cross-linking molecules to expand and stabilize the mechanical property ranges of these gels. Several diamino PEG molecules of varying molecular weight (200, 400, 1000, 3400) were synthesized utilizing carbodiimide chemistry. Sodium alginate was covalently cross-linked with these cross-linking molecules, and mechanical properties of the resulting hydrogels were determined. The elastic modulus of the cross-linked alginates depended on the molecular weight of the cross-linking molecules, and ranged from 10-110 kPa. The theoretical cross-link density in the hydrogels was also varied from 3 to 47% (relative to the carboxylic groups in the alginate) and the mechanical properties were measured. The elastic modulus increased gradually and reached a maximum at a cross-link density of 15%. In summary, covalently coupled hydrogels can be synthesized which exhibit a wide range of mechanical properties, and these materials may be useful in a number of tissue engineering applications.

Imidazole catalyzed silica synthesis: Progress toward understanding the role of histidine in (bio)silicification

2009 ◽  
Vol 24 (5) ◽  
pp. 1700-1708 ◽  
Author(s):  
Mei-Keat Liang ◽  
Siddharth V. Patwardhan ◽  
Elena N. Danilovtseva ◽  
Vadim V. Annenkov ◽  
Carole C. Perry
Keyword(s):  
Molecular Weight ◽  
Silicic Acid ◽  
Catalytic Mechanism ◽  
Synthetic Polymers ◽  
Precipitation Process ◽  
Silica Precipitation ◽  
Silica Synthesis ◽  
Different Molecular Weight

Histidine is an amino acid present in proteins involved in biosilica formation and often found in peptides identified during phage display studies but its role(s) and the extent of its involvement in the silica precipitation process is not fully understood. In this contribution we describe results from an in vitro silicification study conducted using poly-histidine (P-His) and a series of different molecular weight synthetic polymers containing the imidazole functionality (polyvinylimidazole, PVI) for comparison. We show that the presence of imidazole from PVI or P-His is able to catalyze silicic acid condensation; the effect being greater for P-His. The catalytic mechanism is proposed to involve the dual features of the imidazole group—its ability to form hydrogen bonds with silicic acid and electrostatic attraction toward oligomeric silicic acid species.

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.

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