Chromatographic Fractionation of Some Synthetic Elastomers

1948 ◽  
Vol 21 (3) ◽  
pp. 682-683 ◽  
Author(s):  
Ivan Landler
Keyword(s):  
Molecular Weight ◽  
Cellulose Acetate ◽  
Active Carbon ◽  
Low Molecular Weight ◽  
High Polymer ◽  
Acrylonitrile Copolymer ◽  
Molecular Weights ◽  
The Mean ◽  
Mean Molecular Weight ◽  
Poor Solvent

Abstract Mark and Saito were the first to fractionate a high polymer (cellulose acetate) by chromatographic adsorption on blood carbon. They found that molecules of low molecular weight were adsorbed first, and that the mean molecular weight of the product which remained unadsorbed was higher than the original molecular weight. Levi and Giera confirmed this result, but did not succeed in fractionating Buna-S or polyisoprene, for these polymers were eluted by the solvent during the washing operation in the column. The present authors have carried out further experiments in this field with a study of three commercial synthetic elastomers, viz., GR-S (butadienestyrene copolymer), Perbunan-N (butadiene-acrylonitrile copolymer), and Visitanex (polyisobutylene). The polymer was adsorbed by starting with a poor solvent composed of a mixture of toluene and methanol ; the quantity of alcohol added was just below the threshold of precipitation. The adsorbent used was a mixture of 75 per cent of lamp black (80 square meters per gram) and 25 per cent of coarse active carbon. The latter served to prevent agglomeration of the lamp black. The adsorbent was divided into three layers, of 10 grams each. At the end of the tube was a filter of fritted glass. Filtration was carried out under pressure, the rate of flow thereby being maintained constant, The polymers were characterized by their intrinsic viscosities. The molecular weights which were estimated by means of the relation, found experimentally between the molecular weight and viscosity, are only approximate, for this relation holds true only for narrow fractions.

Chlorinated Rubber and Nitrogenous Plasticizers. I. Viscosity of Mixtures of Chlorinated Rubber and Anhydroformaldehyde Urethan

1957 ◽  
Vol 30 (1) ◽  
pp. 274-282
Author(s):  
Michele Giua ◽  
Corrado Mancini
Keyword(s):  
Molecular Weight ◽  
Molecular Weights ◽  
Mixed Solutions ◽  
Quantitative Basis ◽  
The Mean ◽  
Mean Molecular Weight

Abstract The viscosities of solutions of chlorinated rubber in chloroform and in toluene and of mixed solutions of chlorinated rubber and anhydroformaldehyde urethan in toluene were measured. From the data it was possible to determine in an approximate way the mean molecular weight of chlorinated rubber and the mean molecular weights, determined viscometrically, of the mixtures. From the results it was, in turn, possible to derive the α coefficient in the relation of Kuhn. The action of anhydroformaldehyde urethan on chlorinated rubber could then be considered on a quantitative basis.

scholarly journals Effect of ageing on plasma lipoprotein(a) levels

2002 ◽  
Vol 39 (3) ◽  
pp. 237-240 ◽  
Author(s):  
Harukuni Akita ◽  
Miyao Matsubara ◽  
Hitoshi Shibuya ◽  
Hirotoshi Fuda ◽  
Hitoshi Chiba
Keyword(s):  
Molecular Weight ◽  
Coronary Heart Disease ◽  
Risk Factor ◽  
Heart Disease ◽  
The Elderly ◽  
Low Molecular Weight ◽  
Lipoprotein A ◽  
Significant Difference ◽  
The Mean ◽  
Japanese Subjects

Background Lipoprotein(a) [Lp(a)] is a risk factor for atherosclerosis and increases with age. The purpose of this study was to determine the effect of ageing on Lp(a) for three different apo(a) phenotypes. Methods We measured plasma Lp(a) concentrations in 551 unrelated Japanese subjects (20-88 years of age). We performed statistical analyses separately for three apo(a) phenotypes: the low-molecular-weight (LMW) phenotype with the F, B or S1 isoform, the intermediate-molecular-weight (IMW) phenotype with the S2 isoform and the high-molecular-weight (HMW) phenotype with the S3 or S4 isoform. Results For each phenotype, the mean plasma Lp(a) concentration and the frequency of Lp(a) concentrations ≥ 250 mg/L increased with age. Further, a statistically significant difference was always found between the younger subjects (20-39 years of age) and the elderly (over 60 years). The frequency of coronary heart disease increased with age, particularly for the LMW and IMW phenotypes. Conclusions We conclude that ageing elevates plasma Lp(a) concentrations, which may have a role in the prevalence of coronary heart disease in the elderly, especially those with the LMW or IMW phenotypes.

scholarly journals Anticoagulant Properties of a Green Algal Rhamnan-type Sulfated Polysaccharide and Its Low-molecular-weight Fragments Prepared by Mild Acid Degradation

Marine Drugs ◽  
2018 ◽  
Vol 16 (11) ◽  
pp. 445 ◽  
Author(s):  
Xue Liu ◽  
Peng Du ◽  
Xiao Liu ◽  
Sujian Cao ◽  
Ling Qin ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Anticoagulant Activity ◽  
Sulfated Polysaccharide ◽  
Low Molecular Weight ◽  
Thrombin Time ◽  
Acid Degradation ◽  
Molecular Weights ◽  
Green Algal

The active sulfated polysaccharide from seaweed possesses important pharmaceutical and biomedical potential. In the study, Monostroma sulfated polysaccharide (MSP) was obtained from Monostroma angicava, and the low-molecular-weight fragments of MSP (MSP-Fs: MSP-F1–MSP-F6) were prepared by controlled acid degradation. The molecular weights of MSP and MSP-F1–MSP-F6 were 335 kDa, 240 kDa, 90 kDa, 40 kDa, 24 kDa, 12 kDa, and 6.8 kDa, respectively. The polysaccharides were sulfated rhamnans that consisted of →3)-α-l-Rhap-(1→ and →2)-α-l-Rhap-(1→ units with partial sulfation at C-2 of →3)-α-l-Rhap-(1→ and C-3 of →2)-α-l-Rhap-(1→. Anticoagulant properties in vitro of MSP and MSP-F1–MSP-F6 were evaluated by studying the activated partial thromboplastin time, thrombin time, and prothrombin time. Anticoagulant activities in vivo of MSP and MSP-F4 were further evaluated; their fibrin(ogen)olytic activities in vivo and thrombolytic properties in vitro were also assessed by D-dimer, fibrin degradation products, plasminogen activator inhibitior-1, and clot lytic rate assays. The results showed that MSP and MSP-F1–MSP-F4 with molecular weights of 24–240 kDa had strong anticoagulant activities. A decrease in the molecular weight of MSP-Fs was accompanied by a decrease in the anticoagulant activity, and higher anticoagulant activity requires a molecular weight of over 12 kDa. MSP and MSP-F4 possessed strong anticoagulant activities in vivo, as well as high fibrin(ogen)olytic and thrombolytic activities. MSP and MSP-F4 have potential as drug or helpful food supplements for human health.

scholarly journals Evaluation and Management of Women who Have Experienced Stillbirth in Their Previous Pregnancies

2019 ◽  
pp. 1
Author(s):  
Erdem Fadiloglu ◽  
Atakan Tanacan ◽  
Canan Unal ◽  
Mehmet Sinan Beksac
Keyword(s):  
Risk Factors ◽  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Low Dose ◽  
Methylenetetrahydrofolate Reductase ◽  
Post Partum ◽  
Subsequent Pregnancy ◽  
Low Molecular Weight ◽  
Mthfr Polymorphisms ◽  
The Mean

<p><strong>Objective:</strong> To evaluate the subsequent pregnancy outcomes of women who have experienced unexplained stillbirth in their previous gestations.</p><p><strong>Study Design:</strong> This retrospective cohort consisted of 14 pregnancies who had stillbirth (without known risk factors) in their previous pregnancies. These patients had been included in a special preconceptional care program to be evaluated in terms of etiological risk factors for stillbirth. At least one of the risk factors, such as methylenetetrahydrofolate reductase (MTHFR) polymorphisms, hereditary thrombophilias and autoimmune problems, were defined in this study population. After detection of pregnancy, the patients were administered low-dose low-molecular-weight heparin (LMWH) (enoxaparin, 1×2000 Anti-XA IU/0.2 mL/day), low-dose salicylic acid (100 mg/day) and low-dose corticosteroid (methylprednisolone, 1×4 mg/day orally) in necessary cases.</p><p><strong>Results:</strong> Out of 14 pregnancies, 4 (28.5%) ended up with miscarriages at 9, 11, 11 and 15 gestational weeks, respectively. The remaining 10 pregnancies ended up with alive deliveries. The mean gestational week at birth was 36.4±0.51, while the mean birthweight was 2882±381.01 g. Out of 10 pregnancies, only one was diagnosed as IUGR. Only two newborn necessitated hospitalization in the neonatal intensive care unit (NICU) due to respiratory problems. Both newborns were discharged from the NICU without any further complication at the post-partum 5th day. </p><p><strong>Conclusion:</strong> Patients with a prior stillbirth should be screened for MTHFR polymorphisms, autoimmune problems and hereditary thrombophilias, especially in case of absence of any etiological factor. Management of these patients with low-dose aspirin, low-dose low molecular weight heparin and corticosteroids seemed to be beneficial for increasing live birth rates and avoiding obstetric complications.</p>

Microporous Bio-Membrane Materials Based on High Molecular Weight Polylactide and Low Molecular Weight Poly(ethylene glycol)

2012 ◽  
Vol 567 ◽  
pp. 123-126
Author(s):  
Teng Fei Shen ◽  
Man Geng Lu ◽  
Li Yan Liang
Keyword(s):  
Molecular Weight ◽  
Ethylene Glycol ◽  
High Weight ◽  
Low Molecular Weight ◽  
Poly Ethylene Glycol ◽  
Degradation Rates ◽  
Degradation Behaviors ◽  
The Mean ◽  
Poly Ethylene ◽  
Lower Glass Transition Temperature

In this work, microporous membrane biomaterials based on high weight molecular polylactide (PLA) and low molecular weight poly(ethylene glycol) (PEG) using rapid solvent evaporation method were prepared and investigated. The effect of PEG segments added on the thermal and degradation behaviors was studied. According to the results, produced PLA/PEG biomaterial has lower glass transition temperature (Tg)in comparison with neat PLA. It was also found that the degradation rates of the PLA/PEG biomaterials were significantly increased with adding of PEG, which explained by increasing hydrophilic groups. For better porous fixation, CL-blocked polyisocyanate (CL-bp), which was synthesized from reaction of isophorone diisocyanate (IPDI) with dimethylol propionic acid (DMPA) and Trimethylolpropane (TMP) followed by addition of caprolactam (CL), were introduced. The microporous forms were observed by the scanning electron microscope (SEM), which showed the mean diameters of prepared PLA/PEG microporous were around 10μm.

scholarly journals Biodegradation of low molecular weight polyacrylamide under aerobic and anaerobic conditions: effect of the molecular weight

2020 ◽  
Vol 81 (2) ◽  
pp. 301-308 ◽  
Author(s):  
Wenzhe Song ◽  
Yu Zhang ◽  
Amir Hossein Hamidian ◽  
Min Yang
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Carbon Chain ◽  
Anaerobic Treatment ◽  
Low Molecular Weight ◽  
Amino Groups ◽  
Molecular Weights ◽  
Weight One ◽  
Hydrolysis Of ◽  
Aerobic And Anaerobic

Abstract The biodegradation of polyacrylamide (PAM) includes the hydrolysis of amino groups and cleavage of the carbon chain; however, the effect of molecular weight on the biodegradation needs further investigations. In this study, biodegradation of low molecular weight PAM (1.6 × 106 Da) was evaluated in two aerobic (25 °C and 40 °C) and two anaerobic (35 °C and 55 °C) reactors over 100 days. The removal of the low molecular weight PAM (52.0–52.6%) through the hydrolysis of amino groups by anaerobic treatment (35 °C and 55 °C) was much higher than that of the high molecular weight (2.2 × 107 Da, 11.2–17.0%) observed under the same conditions. The molecular weight was reduced from 1.6 × 106 to 6.45–7.42 × 105 Da for the low molecular weight PAM, while the high molecular weight PAM declined from 2.2 × 107 to 3.76–5.87 × 106 Da. The results showed that the amino hydrolysis of low molecular weight PAM is easier than that of the high molecular weight one, while the cleavage of its carbon chain is still difficult. The molecular weights of PAM in the effluents from the two aerobic reactors (25 °C and 40 °C) were further reduced to 4.31 × 105 and 5.68 × 105 Da by the biofilm treatment, respectively. The results would be useful for the management of wastewater containing PAM.

Comparison of exopolysaccharides from mucoid and nonmucoid strains of Clavibacter michiganensis subspecies sepedonicus

1993 ◽  
Vol 39 (3) ◽  
pp. 291-296 ◽  
Author(s):  
Paul J. Henningson ◽  
Neil C. Gudmestad
Keyword(s):  
Molecular Weight ◽  
High Performance ◽  
Size Exclusion ◽  
Enzyme Linked Immunosorbent Assay ◽  
Low Molecular Weight ◽  
Neutral Sugar ◽  
Clavibacter Michiganensis ◽  
Serological Reaction ◽  
Molecular Weights ◽  
Exclusion Chromatography

The exopolysaccharides produced by six strains of Clavibacter michiganensis ssp. sepedonicus were isolated and purified by liquid chromatography. Neutral sugar composition and molecular weights were determined for each polysaccharide fraction, using gas chromatography and high-performance size-exclusion chromatography. The serological reaction of each fraction was tested using enzyme-linked immunosorbent assay. Exopolysaccharide from nonmucoid strains contained only low molecular weight polysaccharides (1.5 × 103 to 1.1 × 104). Exopolysaccharide from mucoid and intermediate strains could be separated into low (4.0 × 103 to 1.1 × 104) molecular weight and high (5.0 × 105 to 1.6 × 106) molecular weight fractions. High molecular weight polysaccharides were composed almost exclusively of galactose, glucose, and fucose. The ratios of these sugars were highly variable among strains. Low molecular weight polysaccharides were primarily composed of galactose with significant and varying amounts of glucose, rhamnose, mannose, and ribose. All polysaccharide fractions except one, produced by a nonmucoid strain, reacted in the immunoassay test.Key words: exopolysaccharide, polysaccharide, Clavibacter, michiganensis, sepedonicus.

Glass Transition and Ultrasonic Relaxation in Polystyrene

1996 ◽  
Vol 455 ◽  
Author(s):  
A. Sahnoune ◽  
L. Piché
Keyword(s):  
Molecular Weight ◽  
Relaxation Time ◽  
Glass Transition ◽  
Low Temperatures ◽  
Relaxation Modulus ◽  
Low Molecular Weight ◽  
Relaxation Model ◽  
Fragility Index ◽  
Molecular Weights ◽  
Ultrasonic Relaxation

ABSTRACTWe present measurements of the glass transition and the ultrasonic relaxation modulus in a series of monodisperse polystyrenes. The temperature dependence of the modulus was analyzed using Havriliak-Negami relaxation model (HN) and Vogel-Tammann-Fulcher equation (VTF) for the relaxation time. The results allowed us to determine the fragility index, m, which decreases with increasing molecular weight, Mn. Furthermore, the relaxation time was found to saturate at high molecular weights and varies as Mnp, in the low molecular weight region. The exponent is p≈2 at high temperatures and p ≈ 7 at low temperatures close to Tg.

scholarly journals Effects Of Environmental Factors On The Dispersion Behavior Of Iron Oxide In Aqueous Solutions With Poly Acrylic Acid

2015 ◽  
Vol 60 (2) ◽  
pp. 1561-1564
Author(s):  
E.-H. Lee ◽  
K.-M. Kim ◽  
W.-Y. Maeng ◽  
D.-H. Hur
Keyword(s):  
Molecular Weight ◽  
Acrylic Acid ◽  
High Molecular Weight ◽  
Low Molecular Weight ◽  
Solution Ph ◽  
Molecular Weights ◽  
Aqueous Suspensions ◽  
Magnetite Particles ◽  
The Stability ◽  
Poly Acrylic Acid

Abstract After preparing aqueous suspensions from magnetite particles with a poly-acrylic acid, we investigated the effects of several experimental parameters. We characterized the stability of the suspensions using visual inspection, sedimentation, adsorption, and thermal stability of the dispersant. The dispersion stability is affected by the solution pH, the concentrations of magnetite particles, the molecular weight, the concentration of the dispersants, and the temperature. The stability of the suspensions increased as the concentration of the dispersant and the temperature increased. In terms of the molecular weights of the dispersant, the suspensions with dispersant of low-molecular weight (1800) were more stable than those of high-molecular weight (250000) at room temperature. However, at high temperature the suspensions with high-molecular weight showed stability. The adsorption efficiency of the dispersant was very low. The dispersant of high-molecular weight showed a higher thermal integrity than that of low-molecular weight. From this work, we obtained the optimum conditions for stable aqueous suspensions of magnetite particles.

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