Rubberlike Properties of Polybutene

1940 ◽  
Vol 13 (3) ◽  
pp. 521-532 ◽  
Author(s):  
W. J. Sparks ◽  
I. E. Lightbown ◽  
L. B. Turner ◽  
P. K. Frolich ◽  
C. A. Klebsattel
Keyword(s):  
Molecular Weight ◽  
Physical State ◽  
Structural Features ◽  
Low Molecular Weight ◽  
General View ◽  
Vinyl Polymers ◽  
Chemical Structures ◽  
Per Se ◽  
Logical Product ◽  
Molecular Weight Form

Abstract Until the last decade the explanation of those properties for which rubber is unique was confined largely to the study of rubber itself. Duplication of these properties involved the synthesis of polymers from isoprene and its immediate homologs. The discovery that chloroprene could be polymerized to a rubberlike substance altered the character of the study and represented a distinct departure in the type of diolefin used. The production of Thiokol, phosphonitrile, and the various vinyl polymers has resulted in the duplication of certain rubberlike physical properties by chemical structures wholly unrelated to rubber. Observation of the behavior of these newer elastics must lead to the conclusion that many physical characteristics of rubber are not inherent in the conformation of the rubber molecule alone. Whitby suggested that any general view of the structure of rubber can be regarded as acceptable only if it is applicable to other elastic colloids. Conversely, those properties of rubber which are not shared by other elastics must be explained by structural features not common to them all. A logical product to consider for the segregation of properties relating to the rubber structure per se and those capable of being shared by other molecules is hydrorubber. This substance has been observed to have certain “rubbery” properties, but unfortunately for comparison it has been prepared only in a degraded or low molecular weight form and therefore (from the standpoint of physical state) is not directly comparable with rubber.

scholarly journals The Purification of Low Molecular Weight Form of Polypeptide Elongation Factor 1 from Pig Liver

1974 ◽  
Vol 249 (15) ◽  
pp. 5008-5010
Author(s):  
Kentaro Iwasaki ◽  
Shigekazu Nagata ◽  
Kiyohisa Mizumoto ◽  
Yoshito Kaziro
Keyword(s):  
Molecular Weight ◽  
Elongation Factor ◽  
Low Molecular Weight ◽  
Pig Liver ◽  
Elongation Factor 1 ◽  
Molecular Weight Form

scholarly journals The interrelations between high- and low-molecular-weight forms of normal and mutant (Krabbe-disease) galactocerebrosidase

1980 ◽  
Vol 189 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Yoav Ben-Yoseph ◽  
Melinda Hungerford ◽  
Henry L. Nadler
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Specific Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Active Form ◽  
Sodium Dodecyl ◽  
Krabbe Disease ◽  
Low Molecular Weight ◽  
Molecular Weight Form

Galactocerebrosidase (β-d-galactosyl-N-acylsphingosine galactohydrolase; EC 3.2.1.46) activity of brain and liver preparations from normal individuals and patients with Krabbe disease (globoid-cell leukodystrophy) have been separated by gel filtration into four different molecular-weight forms. The apparent mol.wts. were 760000±34000 and 121000±10000 for the high- and low-molecular-weight forms (peaks I and IV respectively) and 499000±22000 (mean±s.d.) and 256000±12000 for the intermediate forms (peaks II and III respectively). On examination by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, the high- and low-molecular-weight forms revealed a single protein band with a similar mobility corresponding to a mol.wt. of about 125000. Antigenic identity was demonstrated between the various molecular-weight forms of the normal and the mutant galactocerebrosidases by using antisera against either the high- or the low-molecular-weight enzymes. The high-molecular-weight form of galactocerebrosidase was found to possess higher specific activity toward natural substrates when compared with the low-molecular-weight form. It is suggested that the high-molecular-weight enzyme is the active form in vivo and an aggregation process that proceeds from a monomer (mol.wt. approx. 125000) to a dimer (mol.wt. approx. 250000) and from the dimer to either a tetramer (mol.wt. approx. 500000) or a hexamer (mol.wt. approx. 750000) takes place in normal as well as in Krabbe-disease tissues.

Rheology of Block Copolymers

2007 ◽  
Author(s):  
Chang Dae Han
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Block Copolymers ◽  
Small Angle ◽  
Volume Fraction ◽  
Synthesis Methods ◽  
Chemical Structures ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Molecular Weight Form

Block copolymer consists of two or more long blocks with dissimilar chemical structures which are chemically connected. There are different architectures of block copolymers, namely, AB-type diblock, ABA-type triblock, ABC-type triblock, and AmBn radial or star-shaped block copolymers, as shown schematically in Figure 8.1. The majority of block copolymers has long been synthesized by sequential anionic polymerization, which gives rise to narrow molecular weight distribution, although other synthesis methods (e.g., cationic polymerization, atom transfer radical polymerization) have also been developed in the more recent past. Owing to immiscibility between the constituent blocks, block copolymers above a certain threshold molecular weight form microdomains (10–50 nm in size), the structure of which depends primarily on block composition (or block length ratio). The presence of microdomains confers unique mechanical properties to block copolymers. There are many papers that have dealt with the synthesis and physical/mechanical properties of block copolymers, too many to cite them all here. There are monographs describing the synthesis and physical properties of block copolymers (Aggarwal 1970; Burke and Weiss 1973; Hamley 1998; Holden et al. 1996; Hsieh and Quirk 1996; Noshay and McGrath 1977). Figure 8.2 shows schematically four types of equilibrium microdomain structures observed in block copolymers. Referring to Figure 8.2, it is well established (Helfand and Wasserman 1982; Leibler 1980) that in microphase-separated block copolymers, spherical microdomains are observed when the volume fraction f of one of the blocks is less than approximately 0.15, hexagonally packed cylindrical microdomains are observed when the value of f is between approximately 0.15 and 0.44, and lamellar microdomains are observed when the value of f is between approximately 0.44 and 0.50. Some investigators have observed ordered bicontinuous double-diamonds (OBDD) (Thomas et al. 1986; Hasegawa et al. 1987) or bicontinuous gyroids (Hajduk et al. 1994) at a very narrow range of f (say, between approximately 0.35 and 0.40) for certain block copolymers. Figure 8.2 shows only one half of the symmetricity about f = 0.5. Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) have long been used to investigate the types of microdomain structures in block copolymers.

scholarly journals Synthesis of a Low-Molecular-Weight Form of Exopolysaccharide by Bradyrhizobium japonicum USDA 110

2001 ◽  
Vol 67 (2) ◽  
pp. 1011-1014 ◽  
Author(s):  
Heather A. Louch ◽  
Karen J. Miller
Keyword(s):  
Molecular Weight ◽  
Bradyrhizobium Japonicum ◽  
Compositional Analysis ◽  
Mass Spectrometry Analysis ◽  
Low Molecular Weight ◽  
Nuclear Magnetic Resonance Analysis ◽  
Spectrometry Analysis ◽  
Resonance Analysis ◽  
Dimeric Form ◽  
Molecular Weight Form

ABSTRACT A novel extracellular low-molecular-weight polysaccharide was detected as a contaminant within extracellular cyclic β-1,6-β-1,3-glucan preparations from Bradyrhizobium japonicum USDA 110 cultures. Compositional analysis, methylation analysis, and nuclear magnetic resonance analysis revealed that this low-molecular-weight polysaccharide was composed of the same pentasaccharide repeating unit previously described for the high-molecular-weight form of the exopolysaccharide (EPS) synthesized by B. japonicum strains. Mass spectrometry analysis indicated that the size of this low-molecular-weight form of EPS was consistent with a dimeric form of the pentasaccharide repeating unit.

Antithrombotic and Anticoagulant Activities of a Low Molecular Weight Fucoidan by the Subcutaneous Route

1999 ◽  
Vol 81 (03) ◽  
pp. 391-395 ◽  
Author(s):  
S. Colliec Jouault ◽  
S. Mauray ◽  
J. Theveniaux ◽  
C. Sternberg ◽  
Boisson Vidal ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Subcutaneous Injection ◽  
Thrombin Generation ◽  
Sulfated Polysaccharides ◽  
Low Molecular Weight ◽  
High Molecular Weight Fraction ◽  
Antithrombotic Activity ◽  
Single Subcutaneous Injection ◽  
Chemical Structures

SummaryFucoidans (high-molecular-weight sulfated polysaccharides extracted from brown seaweeds) have anticoagulant and antithrombotic effects. They inhibit thrombin by catalyzing both serpins (antithrombin and heparin cofactor II) according to their chemical structures and origins. In this study, a low-molecular-weight (LMW) fucoidan of 8 kDa was obtained by chemical degradation of a high-molecular-weight fraction. The antithrombotic and anticoagulant activities of this new compound were compared to those of a low-molecular-weight heparin (LMWH), dalteparin, following subcutaneous administration to rabbits. This LMW fucoidan exhibited dose-related venous antithrombotic activity, with an ED80 of about 20 mg/kg, 2 h after a single subcutaneous injection. Its activity was comparable to that of dalteparin (close to 200 anti-Xa IU/kg) and was maximal 30 min after a single subcutaneous injection. The activity remained stable (about 70%) from 1 to 4 h after injection, but disappeared by 8 h. The antithrombotic activity was not associated with either a prolongation of the thrombin clotting time (TCT) or an increase in anti-Xa activity, contrary to dalteparin. A slight prolongation of APTT occurred with both compounds. This venous antithrombotic activity was associated with a decrease in ex vivo thrombin generation and with a significant increase in the lag phase in a thrombin generation test. LMW fucoidan thus has potent antithrombotic activity and a potentially weaker haemorrhagic effect (i.e. a smaller effect on coagulation tests and a smaller prolongation of the bleeding time) than dalteparin.

Immunoaffinity Chromatography of Canine High-Molecular-Weight Renin: Partial Purification and Characterization

1983 ◽  
Vol 65 (2) ◽  
pp. 117-120 ◽  
Author(s):  
Fumihiko Ikemoto ◽  
Victor J. Dzau ◽  
Edgar Haber ◽  
Kazuo Takaori ◽  
Kenjiro Yamamoto
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Specific Activity ◽  
Immunoaffinity Chromatography ◽  
Partial Purification ◽  
Low Molecular Weight ◽  
Specific Method ◽  
Disulphide Bonds ◽  
Binding Substance ◽  
Molecular Weight Form

1. Canine high-molecular-weight renin (mol. wt. 60 000) is believed to be a complex of renin (low-molecular-weight form, mol. wt. 40 000) and renin-binding substance. The immunocross-reactivity of high-molecular-weight renin and low-molecular-weight renin was demonstrated by using antibodies specific to low-molecular-weight renin. 2. Immunoaffinity chromatography with renin-specific antibodies coupled to Sepharose provided a simple and specific method for isolation of high-molecular-weight renin. High-molecular-weight renin with a specific activity of 137 600 ng of ANG I h−1 mg−1 of protein (19.6 Goldblatt units/mg of protein) was obtained. 3. This high-molecular-weight renin was stable in dithiothreitol (25 mmol/l), suggesting that disulphide bonds may not be involved in the binding mechanism between low-molecular-weight renin and renin-binding substance. 4. However, exposure to low pH (3.0) resulted in conversion of high-molecular-weight renin into the low-molecular-weight form.

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