Influence of the degree of polymerisation and of the architecture on the elastic properties of new polyurea elastomers

RSC Advances ◽  
2015 ◽  
Vol 5 (9) ◽  
pp. 6758-6770 ◽  
Author(s):  
Antoni Sánchez-Ferrer ◽  
Daniel Rogez ◽  
Philippe Martinoty
Keyword(s):  
Molecular Weight ◽  
Elastic Properties ◽  
Chemical Nature ◽  
Degree Of Polymerisation ◽  
End Groups

The elastic properties of new polyurea elastomers have been studied by varying the segmental molecular weight and the chemical nature of the polymer end groups showing up to two plateaus.

Relation between Molecular Weights and Physical Properties of Rubber Fractions

1941 ◽  
Vol 14 (3) ◽  
pp. 580-589 ◽  
Author(s):  
G. Gee ◽  
L. R. G. Treloar
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Physical Properties ◽  
High Molecular Weight ◽  
Elastic Properties ◽  
Elastic Material ◽  
Experimental Results ◽  
Molecular Weights ◽  
High Elasticity ◽  
Latex Rubber

Abstract As high elasticity is a property possessed only by substances of high molecular weight, it is of interest to enquire into the relation between the elastic properties of a highly elastic material such as rubber and its molecular weight. An investigation on these lines has been made possible through the work of Bloomfield and Farmer, who have succeeded in separating natural rubber into fractions having different average molecular weights. The more important physical properties of these fractions have been examined with the object of determining which of the properties are dependent on molecular weight and which are not. Fairly extensive observations were made on the fractions from latex rubber referred to as Nos. 2, 3 and 4 by Bloomfield and Farmer, and some less extensive observations were carried out on the less oxygenated portion of fraction No. 1 obtained from crepe rubber (called hereafter 1b) . Before considering these experimental results, and their relation to the molecular weights of the fractions, it will be necessary to refer briefly to the methods used for the molecular-weight determinations, and to discuss the significance of the figures obtained.

scholarly journals The effect of molecular weight on the porosity of hypercrosslinked polystyrene

2015 ◽  
Vol 6 (41) ◽  
pp. 7280-7285 ◽  
Author(s):  
Thanchanok Ratvijitvech ◽  
Michael Barrow ◽  
Andrew I. Cooper ◽  
Dave J. Adams
Keyword(s):  
Molecular Weight ◽  
Hypercrosslinked Polystyrene ◽  
Degree Of Polymerisation ◽  
Microporous Polymers ◽  
Surface Areas

Microporous polymers can be prepared by crosslinking polystyrenes, with the surface areas being dependent on the degree of polymerisation.

scholarly journals Solid-State Polymerization of Poly(Ethylene Furanoate) Biobased Polyester, III: Extended Study on Effect of Catalyst Type on Molecular Weight Increase

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 438 ◽  
Author(s):  
Yosra Chebbi ◽  
Nejib Kasmi ◽  
Mustapha Majdoub ◽  
George Papageorgiou ◽  
Dimitris Achilias ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Solid State ◽  
Intrinsic Viscosity ◽  
Weight Increase ◽  
Degree Of Crystallinity ◽  
Solid State Polymerization ◽  
End Groups ◽  
Poly Ethylene ◽  
Molecular Weight Increase

In this study, the synthesis of poly(ethylene furanoate) (PEF), catalyzed by five different catalysts—antimony acetate (III) (Sb Ac), zirconium (IV) isopropoxide isopropanal (Zr Is Ip), antimony (III) oxide (Sb Ox), zirconium (IV) 2,4-pentanedionate (Zr Pe) and germanium (IV) oxide (Ge Ox)—via an industrially common combination of melt polymerization and subsequent solid-state polymerization (SSP) is presented. In all reactions, proper amounts of 2,5-dimethylfuran-dicarboxylate (DMFD) and ethylene glycol (EG) in a molar ratio of DMFD/EG= 1/2 and 400 ppm of catalyst were used. Polyester samples were subjected to SSP procedure, under vacuum application, at different reaction times (1, 2, 3.5, and 5 h) and temperatures of 190, 200, and 205 °C. Carboxyl end-groups concentration (–COOH), intrinsic viscosity (IV), and thermal properties, via differential scanning calorimetry (DSC), were measured for all resultant polymers to study the effect of the used catalysts on the molecular weight increase of PEF during SSP process. As was expected, it was found that with increasing the SSP time and temperature, the intrinsic viscosity and the average molecular weight of PEF steadily increased. In contrast, the number of carboxyl end-groups content showed the opposite trend as intrinsic viscosity, that is, gradually decreasing during SSP time and temperature increase. It is worthy to note that thanks to the SSP process an obvious and continuous enhancement in the thermal properties of the prepared PEF samples was attained, in which their melting temperatures (Tm) and degree of crystallinity (Xc) increase progressively with increasing of reaction time and temperature. To predict the time evolution of polymers IV, as well as the hydroxyl and carboxyl content of PEF polyesters during the SSP, a simple kinetic model was developed. From both the theoretical simulation results and the experimental measurements, it was demonstrated that surely the Zr Is Ip catalyst shows the best catalytic characteristics compared to all other used catalysts herein, that is, leading in reducing—in a spectacular way—the activation energy of the involved both transesterification and esterification reactions during SSP.

Pressure and molecular-weight dependences of elastic properties of polystyrene polymers studied by Brillouin spectroscopy

2017 ◽  
Vol 17 (11) ◽  
pp. 1396-1400 ◽  
Author(s):  
Byoung Wan Lee ◽  
Min-Seok Jeong ◽  
Jong Sun Choi ◽  
Jaehoon Park ◽  
Young Ho Ko ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Elastic Properties ◽  
Brillouin Spectroscopy

scholarly journals Some Guidelines for the Synthesis and Melting Characterization of Azide Poly(ethylene glycol) Derivatives

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1269
Author(s):  
Daniel González-Fernández ◽  
Mercedes Torneiro ◽  
Massimo Lazzari
Keyword(s):  
Molecular Weight ◽  
Ethylene Glycol ◽  
Average Molecular Weight ◽  
Size Exclusion ◽  
Degree Of Crystallinity ◽  
Specific Class ◽  
Poly Ethylene Glycol ◽  
End Groups ◽  
Poly Ethylene

We provide fundamental guidelines in the form of a tutorial to be taken into account for the preparation and characterization of a specific class of poly(ethylene glycol) (PEG) derivatives, namely azide-terminated PEGs. Special attention is given to the effect of these chain end groups and their precursors on properties affecting the PEGylation of proteins, nanoparticles and nanostructured surfaces. Notwithstanding the presence of 13C satellite peaks, we show that 1H NMR enables not only the routine quantitative determination of chain-end substitution, but is also a unique method to calculate the absolute number average molecular weight of PEG derivatives. In the use of size exclusion chromatography to get molecular weight distributions, we highlight the importance of distinguishing between eventual secondary reactions involving molecular weight changes and the formation of PEG complexes due to residual amounts of metal cations from reactants. Finally, we show that azide end groups affect PEG melting behavior. In contrast to oxygen-containing end groups, azides do not interact with PEG segments, thus inducing defect formation in the crystal lattice and the reduction of crystal sizes. Melting temperature and degree of crystallinity decrease become especially relevant for PEGs with very low molecular weight, and its comprehension is particularly important for solid-state applications.

Structural studies of oligosilanes produced by catalytic dehydrogenative coupling of primary organosilanes

1987 ◽  
Vol 65 (8) ◽  
pp. 1804-1809 ◽  
Author(s):  
C. Aitken ◽  
J. F. Harrod ◽  
U. S. Gill
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Gel Permeation Chromatography ◽  
Structural Studies ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Dehydrogenative Coupling ◽  
Weight Distributions ◽  
Gel Permeation ◽  
End Groups

The structures of some poly(organosilylenes), [Formula: see text] (R = Ph, p-tolyl, n-hexyl, and benzyl), produced by catalytic dehydrogenative coupling of primary silanes have been studied by infrared, nuclear magnetic resonance, and mass spectroscopies. These results, combined with data on molecular weights and molecular weight distributions from vapour pressure osmometry and gel permeation chromatography, lead to the conclusion that the polymers are linear and have SiH2R end groups. The polymers all have degrees of polymerization of ca. 10 and very narrow molecular weight dipersions. Some possible features of the mechanism that gives rise to this behaviour are discussed.

The Stability of Abiarana Gutta-Percha Latex

1937 ◽  
Vol 10 (2) ◽  
pp. 272-278
Author(s):  
F. K. Daniel ◽  
H. Freundlich ◽  
K. Söllner
Keyword(s):  
Molecular Weight ◽  
Electric Current ◽  
Chemical Nature ◽  
Electrical Charge ◽  
Gutta Percha ◽  
Large Molecular Weight ◽  
Time Average ◽  
The Difference ◽  
The Stability ◽  
Average Size

Abstract 1. The latex of Abiarana gutta-percha is more stable than that of Hevea. In the absence of preservatives Abiarana latex is stable for many months, while Hevea coagulates readily in a few hours. On addition of electrolytes, Abiarana only creams up and is readily and reversibly redispersed; Hevea is coagulated jrreversibly. Under the influence of the electric current Abiarana does not form a coherent skin on the anode; Hevea does so easily. 2. The stability of Abiarana latex is due to a protecting substance reversibly adsorbed on the particles. This substance may be removed by allowing the particles to cream-up repeatedly and by separating the serum from the particles. The serum of Abiarana (or the whole latex) added to Hevea latex strongly protects the latter and causes it to behave like Abiarana latex. 3. A similar protecting action in small concentrations cannot be produced by substances such as gelatin, peptones, lysalbinic acid, starch, etc. The chemical nature of the protecting substance could not be identified. It must have a large molecular weight, since it does not diffuse through membranes. 4. The reversible creaming-up of Abiarana latex is influenced by the cations of the electrolytes added according to their valency, in agreement with the fact that the particles are negatively charged. H+-ion and ter- and tetravalent cations are able to reverse the electrical charge of the particles. 5. The difference in creaming velocity due to different electrolyte concentrations (i. e., to different degree of discharge) seems to depend on time average size and number of aggregates of particles which are formed.

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