Isoprene and Rubber. Part 45. Viscosity Measurements of Solutions of Rubber and Hydrorubber in Various Solvents

1936 ◽  
Vol 9 (4) ◽  
pp. 579-584
Author(s):  
H. Staudinger ◽  
H. P. Mojen
Keyword(s):  
Carbon Tetrachloride ◽  
Chain Length ◽  
Homologous Series ◽  
Chlorinated Solvents ◽  
Cellulose Derivatives ◽  
Specific Viscosity ◽  
Molecular Weights ◽  
Rubber Part ◽  
Viscous Solutions ◽  
Chain Lengths

Abstract It has been observed many times that solutions of the same concentration of rubber in various solvents show marked differences in viscosity. For example, solutions of rubber in chlorinated solvents such as carbon tetrachloride have higher viscosities than do solutions of the same concentration in benzene or benzine. These differences in viscosity are attributable to the fact that the rubber molecules are solvated in different ways in the various solvents. It may be further assumed that in a particular homologous series of polymers, all members, i. e., substances of both high and low molecular weights, are solvated in the same solvent in the same way, for only in this way is it possible to believe that the specific viscosity of solutions of like concentration increases with increase in the chain length, as has been found to be true of cellulose derivatives. In the previous experiments with squalene and hydrosqualene (cf. preceding article), the constants necessary for calculating molecular weights and chain member indices n were determined. The constants for carbon tetrachloride are higher than those for benzene. In the case of squalene, therefore, as in the case of rubber, carbon tetrachloride gives more viscous solutions than does benzene. If, now, rubbers and hydrorubbers are solvated in the same way as squalene and hydrosqualene, then the same chain lengths of an homologous series of rubber polymers would be obtained by calculations using constants derived from the simple compounds of the chain member index, and from this the degrees of polymerization, are calculated by means of these constants in the formula:

Molecular Weight and Chain-Length of Natural and Synthetic Rubber

1934 ◽  
Vol 7 (1) ◽  
pp. 34-39 ◽  
Author(s):  
A. J. Wildschut
Keyword(s):  
Chain Length ◽  
Freezing Point ◽  
Specific Viscosity ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Synthetic Rubber ◽  
The Subject ◽  
Molecular Substances ◽  
Very High

Abstract The determination of the chain-length of high molecular substances, as, e.g., rubber and gutta-percha, has lately been the subject of many investigations, though as yet the problem has not been definitely solved. The ordinary methods—measurements of the raising of the boiling point and of the depression of the freezing point—can be used only for molecular weights of some thousands, and there always remains a large gap between these compounds and the far greater natural ones. To bridge over this gap Staudinger has developed a supposition according to which it is possible to determine very high molecular weights by means of a viscosimetric method. This method depends on the known fact that for dilute solutions, in which the molecules do not hinder each other (so-called sol-solutions), the specific viscosity is proportional to the length of the molecule. For homologs we have:

Isoprene and Rubber. Part 44. Viscosity Measurements of Squalene and Hydrosqualene Solutions

1936 ◽  
Vol 9 (4) ◽  
pp. 573-578
Author(s):  
H. Staudinger ◽  
H. P. Mojen
Keyword(s):  
Physical Properties ◽  
General Relation ◽  
Basic Structure ◽  
Degree Of Polymerization ◽  
Specific Viscosity ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Rubber Part

Abstract The physical properties of highly polymerized substances, which are composed of fiber molecules, depend on the lengths of the chains of these fiber molecules. Thus tensile strength, elasticity, tendency to swell in solvents, and above all viscosity, are dependent on the length of chain of the particular substance. Among the substances, the properties of which vary thus, are rubber, gutta-percha, and balata. Since the length of fiber molecules can vary within wide limits, such physical properties as those mentioned above show wide variations in the case of rubber, gutta-percha, and balata. This is evident for example by a comparison of the properties of unmasticated rubber, which consists of long fiber molecules of a degree of polymerization of 2000, with the properties of masticated rubber, the greatly dissociated molecules of which have a degree of polymerization of only 500. The determination of the length of the fiber molecules is therefore of great importance in the case of highly polymerized substances. It has already been proved in past experiments with members of a series of homologous polymers, i. e., of substances the macromolecules of which have the same basic structure and differ only in length, that the molecular weights can be determined from viscosity measurements. This determination is based on the fact that there is a general relation between the specific viscosity and the length of the dissolved molecules, which can be expressed by the formula:

scholarly journals Analysis of Network Structures in Thiol-Ene UV Curing System Using Reworkable Resins

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 5 ◽  
Author(s):  
Haruyuki Okamura ◽  
Masashi Yamagaki ◽  
Kyohei Nakata
Keyword(s):  
Chain Length ◽  
Uv Curing ◽  
Size Exclusion ◽  
Network Structures ◽  
Thiol Compounds ◽  
Molecular Weights ◽  
Degraded Samples ◽  
Exclusion Chromatography ◽  
Chain Lengths ◽  
Acrylate Monomers

An analysis of the network structures in thiol-ene UV curing resins was carried out using reworkable resins composed of di(meth)acrylate monomers having tertiary ester linkages. The effect of the functionality of the thiols, the functional ratio of the thiol and ene functions, their conversions and curing atmosphere on the chain lengths was discussed. A mixture of (meth)acrylates, thiol compounds, a photoradical initiator, and a photoacid generator was cured by irradiation at 365 nm. The cured samples were degraded by heating after irradiation at 254 nm. Size exclusion chromatography (SEC) and 1H NMR analyses of the degraded samples were carried out after the methylation. The crosslinking conditions strongly affected the network structures. The degraded samples have molecular weights between 250 and 2700. The molecular weights of the degraded resins increased with the functionality of the thiol compounds. The chain length dependence suggests that thiol compounds with a high functionality have a low reactivity due to steric hindrance. The chain lengths of the degraded networks were nearly proportional to the concentration of the (meth)acrylate monomers. The addition of reactive diluents enhanced the reactivity and increased the chain length.

Isoprene and Rubber. Part 20. The Colloidal Nature of Rubber, Gutta-Percha, and Balata

1930 ◽  
Vol 3 (4) ◽  
pp. 586-595
Author(s):  
H. Staudinger
Keyword(s):  
Molecular Weight ◽  
Characteristic Viscosity ◽  
Specific Viscosity ◽  
Decomposition Products ◽  
Molecular Weights ◽  
Gutta Percha ◽  
Viscosity Increase ◽  
Preceding Work ◽  
Rubber Part

Abstract I. The Molecular Weight of Rubber, Gutta-Percha, and Balata In the preceding work the molecular weight of rubber and balata was calculated on the basis of relations between specific viscosity ηsp and molecular weight which are shown by semi-colloidal decomposition products, on the assumption that this relation is also true for eucolloids. The value ηr−1 was taken as the specific viscosity, i. e., the characteristic viscosity increase of a substance of definite concentration and known solvent. The expression “specific viscosity” has already been used by J. Duclaux. In viscosity investigations of nitrocellulose solutions he represents this by a constant K which is calculated from the relations of the change of viscosity at various concentrations derived by Arrhenius: Based on these constants, nitrocelluloses show different average molecular weights for the increase in viscosity, that is, this constant K is greater with high molecular products than with low. In the following, this constant represents not the specific viscosity, but the viscosity-concentration constant Kc; the earlier constant Km which, on the basis of the formula: expressed the relation between the specific viscosity and the molecular weight, is called the viscosity-molecular weight constant.

Isoprene and Rubber. Part 34. Molecules or Micelles in a Rubber Solution

1932 ◽  
Vol 5 (3) ◽  
pp. 265-277
Author(s):  
H. Staudinger ◽  
H. F. Bondy
Keyword(s):  
Colloidal Solutions ◽  
Dilute Solutions ◽  
Pure Nitrogen ◽  
Viscosity Measurements ◽  
Molecular Weights ◽  
Colloid Particles ◽  
Rubber Part ◽  
Complete Exclusion ◽  
The Individual ◽  
Viscous Solutions

Abstract Measurements of the Viscosity of Rubber Solutions In the literature may be found numerous measurements of the viscosity of rubber solutions, the object of which was to throw light on the nature of colloidal solutions and changes in these solutions by various operations. These investigations give no insight into the structure of colloid particles and the reason for changes in rubber solutions because they are based on false assumptions, particularly the assumption that rubber has a micellar structure. Often highly viscous solutions were studied, and though these appeared to be of special interest to the colloid chemist, they were unsuited for such investigations, for they are gel solutions in which the structure of the colloid particles is much more difficult to explain than is that in dilute solutions (sol solutions), where the molecules have freedom of movement and do not disturb one another. The earlier works also contain references to the sensitivity of rubber to oxygen, though no special precautions were ever taken in the measurements to exclude oxygen; in fact this was unnecessary as a rule, for crude rubber solutions are much more stable, because of anticatalysts present, than solutions of pure rubber in which these have been removed. Pure rubber was prepared by the method of Pummerer and Pahl and, as described in the following work, was separated by fractional extraction into portions of different average molecular weights. Viscosity measurements of the individual fractions were then carried out under various conditions. The study of the rubber solution, like that of the balata solution, must be carried out with complete exclusion of air, and the solvent (tetralin or benzene) must be distilled in an atmosphere of pure nitrogen and be freed of oxygen. The filtration of the rubber solution, the filling of the viscosimeter, as well as the measurements themselves, are likewise made in an atmosphere of pure nitrogen. Measurements were taken in the Ubbelohde viscosimeter at different pressures, as a rule at 10.30 and 60 cm. mercury pressure. Very dilute solutions were also measured in the Ostwald viscosimeter, since the deviations from the Hagen-Poiseuille law are of no great importance at low concentration. Finally, it should be mentioned that these special precautions during the viscosity measurements, above all the careful exclusion of air, are necessary only in the case of rubber, not with the saturated hydrocarbons, polystyrene, and hydrorubber.

Chain-Length Distribution Functions during Polymerization

1954 ◽  
Vol 27 (3) ◽  
pp. 622-628 ◽  
Author(s):  
W. F. Watson
Keyword(s):  
Reaction Mechanism ◽  
Chain Length ◽  
Length Distribution ◽  
Kinetic Scheme ◽  
Distribution Functions ◽  
Average Chain Length ◽  
Chain Length Distribution ◽  
Molecular Weights ◽  
Measurable Rate ◽  
Chain Lengths

Abstract Functions for the distribution of chain lengths of a polymer formed during polymerization have been evaluated in terms of the directly measurable rate and rate of initiation, or the single equivalent measurement of number-average chain length. No details of the reaction mechanism are required, except for the occurrence of termination by combination of polymer radicals. This is in contrast to the usual derivation of distribution functions from the postulated kinetic scheme. The three types of termination are considered, (1) combination absent, (2) combination predominant, and (3) a mixture of combination with other modes of termination. The application to copolymerization is outlined. Relationships between the various average molecular weights are considered.

scholarly journals Effect of terminal chain length on the helical twisting power in achiral bent-core molecules doped in a cholesteric liquid crystal

RSC Advances ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 1292-1295 ◽  
Author(s):  
Byeong-Cheon Kim ◽  
Martin Walker ◽  
Seong-Yong Jo ◽  
Mark R. Wilson ◽  
Hideo Takezoe ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Chain Length ◽  
Homologous Series ◽  
Cholesteric Liquid Crystal ◽  
Chain Lengths ◽  
Helical Twisting Power ◽  
Terminal Chain

We prepared a homologous series of achiral bent-core (BC) liquid crystals with different terminal alkoxy chain lengths, n (BC-n), and evaluated the helical twisting power (HTP) of the BC-n doped in a cholesteric liquid crystal.

Immuno-compatibility of desaminotyrosine and desaminotyrosyl tyrosine functionalized star-shaped oligo(ethylene glycol)s with different molecular weights

2015 ◽  
Vol 1718 ◽  
pp. 97-102 ◽  
Author(s):  
Toralf Roch ◽  
Konstanze K. Julich-Gruner ◽  
Axel T. Neffe ◽  
Nan Ma ◽  
Andreas Lendlein
Keyword(s):  
Aqueous Solution ◽  
Ethylene Glycol ◽  
Average Molecular Weight ◽  
Molecular Weights ◽  
Immunological Effects ◽  
Microbial Products ◽  
Low Levels ◽  
Chain Lengths ◽  
Immunological Evaluation

ABSTRACTPolymer-based therapeutic strategies require biomaterials with properties and functions tailored to the demands of specific applications leading to an increasing number of newly designed polymers. For the evaluation of those new materials, comprehensive biocompatibility studies including cyto-, tissue-, and immunocompatibility are essential. Recently, it could be demonstrated that star-shaped amino oligo(ethylene glycol)s (sOEG) with a number average molecular weight of 5 kDa and functionalized with the phenol-derived moieties desaminotyrosine (DAT) or desaminotyrosyl tyrosine (DATT) behave in aqueous solution like surfactants without inducing a substantial cytotoxicity, which may qualify them as solubilizer for hydrophobic drugs in aqueous solution. However, for biomedical applications the polymer solutions need to be free of immunogenic contaminations, which could result from inadequate laboratory environment or contaminated starting material. Furthermore, the materials should not induce uncontrolled or undesired immunological effects arising from material intrinsic properties. Therefore, a comprehensive immunological evaluation as perquisite for application of each biomaterial batch is required. This study investigated the immunological properties of sOEG-DAT(T) solutions, which were prepared using sOEG with number average molecular weights of 5 kDa, 10 kDa, and 20 kDa allowing analyzing the influence of the sOEG chain lengths on innate immune mechanisms. A macrophage-based assay was used to first demonstrate that all DAT(T)-sOEG solutions are free of endotoxins and other microbial contaminations such as fungal products. In the next step, the capacity of the different DAT(T)-functionalized sOEG solutions to induce cytokine secretion and generation of reactive oxygen species (ROS) was investigated using whole human blood. It was observed that low levels of the pro-inflammatory cytokines interleukin(IL)-1β and IL-6 were detected for all sOEG solutions but only when used at concentrations above 250 µg·mL-1. Furthermore, only the 20 kDa sOEG-DAT induced low amounts of ROS-producing monocytes. Conclusively, the data indicate that the materials were not contaminated with microbial products and do not induce substantial immunological adverse effectsin vitro,which is a prerequisite for future biological applications.

scholarly journals Phenylalkylammonium passivation enables perovskite light emitting diodes with record high-radiance operational lifetime: the chain length matters

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuwei Guo ◽  
Sofia Apergi ◽  
Nan Li ◽  
Mengyu Chen ◽  
Chunyang Yin ◽  
...  
Keyword(s):  
Chain Length ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Light Emitting Diodes ◽  
Surface Defects ◽  
Theoretical Modelling ◽  
Ion Migration ◽  
Light Emitting ◽  
Operational Lifetime ◽  
Chain Lengths

AbstractPerovskite light emitting diodes suffer from poor operational stability, exhibiting a rapid decay of external quantum efficiency within minutes to hours after turn-on. To address this issue, we explore surface treatment of perovskite films with phenylalkylammonium iodide molecules of varying alkyl chain lengths. Combining experimental characterization and theoretical modelling, we show that these molecules stabilize the perovskite through suppression of iodide ion migration. The stabilization effect is enhanced with increasing chain length due to the stronger binding of the molecules with the perovskite surface, as well as the increased steric hindrance to reconfiguration for accommodating ion migration. The passivation also reduces the surface defects, resulting in a high radiance and delayed roll-off of external quantum efficiency. Using the optimized passivation molecule, phenylpropylammonium iodide, we achieve devices with an efficiency of 17.5%, a radiance of 1282.8 W sr−1 m−2 and a record T50 half-lifetime of 130 h under 100 mA cm−2.

Degrees of order of solubilized alkanes, alcohols, carboxylates, and carboxylic acids in oriented lyomesophases

1977 ◽  
Vol 55 (12) ◽  
pp. 2404-2410 ◽  
Author(s):  
Douglas M. Chen ◽  
Fred Y. Fujiwara ◽  
Leonard W. Reeves
Keyword(s):  
Carboxylic Acids ◽  
Chain Length ◽  
Linear Increase ◽  
Short Chain ◽  
Appreciable Amount ◽  
Linear Region ◽  
Short Chain Length ◽  
Chain Lengths ◽  
Degree Of Order ◽  
Limiting Value

The degree of order of solubilized molecules and ions in oriented lyomesophases has been determined at specifically deuterated C—D bond axes from the quadrupole splitting of the deuterium magnetic resonance. Mixtures at low concentration of specifically deuterated alkanes, alcohols, carboxylic acids, and carboxylates of different chain length have been observed in host cationic and anionic lyomesophases. The degree of order of a given C—D position in alcohols increases strongly with chain length up to a length comparable with the host detergent. A broad series of carboxylic acids and carboxylate ions from C2 to C16 have been deuterated in the α position. The α-C—D bond axis in the solubilisate increases in order with chain length, the anion having lower order than the parent acid. An accurately linear increase in the degree of order of the α position is observed for intermediate chain lengths. At chain lengths approximately equal to the host chain lengths the α position reaches a limiting value in the degree of order and further segments do not influence the order. At short chain lengths the degree of order is less than that predicted from extrapolation of order in the linear region. This has been interpreted in terms of distribution into the aqueous compartment by the solubilisates of short chain length. Acetic acid and the acetate, propionate, butanoate, and pentanoate ions spend an appreciable amount of time in the aqueous region. An estimate has been made of these distributions based on reasonable assumptions.

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