Metal Oxide Trialkylsilyloxide Polymers. Part VI. Aluminum Oxide Trimethylsilyloxides

1971 ◽  
Vol 49 (13) ◽  
pp. 2310-2314 ◽  
Author(s):  
D. C. Bradley ◽  
J. W. Lorimer ◽  
C. Prevedorou-Demas
Keyword(s):  
Metal Oxide ◽  
Aluminum Oxide ◽  
Linear Dependence ◽  
Degree Of Polymerization ◽  
Oh Groups ◽  
Molecular Weights ◽  
Controlled Conditions ◽  
Adjacent Unit ◽  
Oxygen Atoms

Tris(trimethylsilyloxy)aluminum, [Al(OSiMe3)3]2, was hydrolyzed under controlled conditions in dioxane at 25 °C. The soluble initial products [AlOx(OH)z(OSiMe3)3−2x−z]n, with x = 0.03–0.65, underwent disproportionation when heated at 120–150 °C under vacuum to give final products with x = 0.8–1.1. Molecular weights were determined by cryoscopy in cyclohexane, and the linear dependence of 1/n on x was combined with an extension of the theory of regular polymer series to show that the number of OH groups, z, was small compared to the number of bridging oxygen atoms, x, per Al atom. The initial products consist of dimeric units, each linked to an adjacent unit by one or two oxygen bridges between aluminum atoms. The degree of polymerization is 1 to 4, based on the dimer unit. The final products have much higher degrees of polymerization (10–40, based on the dimer), and appear to contain a higher proportion of Al—O—Al bridges.

Metal oxide trialkylsilyloxide polymers. Part V. Further studies on titanium oxide triethylsilyloxide polymers

1969 ◽  
Vol 47 (22) ◽  
pp. 4113-4116 ◽  
Author(s):  
D. C. Bradley ◽  
J. W. Lorimer ◽  
C. Prevedorou-Demas
Keyword(s):  
Metal Oxide ◽  
Titanium Oxide ◽  
Linear Dependence ◽  
High Vacuum ◽  
Molecular Weights ◽  
Controlled Conditions

Tetrakis(triethylsilyloxy)titanium, Ti(OSiEt3)4, was hydrolyzed under controlled conditions in dioxane at 60 °C. The soluble initial products [TiOx(OSiEt3)4−2x]n, with x = 0.1–0.5, underwent disproportionation when heated at 65 °C under high vacuum to give Ti(OSiEt3)4 and products with values of x in the range 0.4–1.4. Molecular weights were determined by cryoscopy in cyclohexane, and the linear dependence of 1/n on x was used as a basis for structural proposals. The results are compared with those obtained previously for the initial products of hydrolysis.

METAL OXIDE TRIALKYLSILYLOXIDE POLYMERS (POLYTRIALKYLSILOXANOMETALLOXANES): PART I. TITANIUM OXIDE TRIMETHYLSILYLOXIDE POLYMERS

1963 ◽  
Vol 41 (3) ◽  
pp. 629-635 ◽  
Author(s):  
D. C. Bradley ◽  
C. Prevedorou-Demas
Keyword(s):  
Molecular Weight ◽  
Metal Oxide ◽  
Titanium Oxide ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Degree Of Hydrolysis ◽  
Controlled Conditions

Tetrakis-(trimethylsilyloxy)-titanium Ti(OSiMe3)4 has been hydrolyzed under controlled conditions in dioxane. The initial products of hydrolysis undergo facile disproportionation, e.g. 3Ti2O(OSiMe3)6 → 4Ti(OSiMe3)4 + polymeric Ti2O3(OSiMe3)2. Molecular weight determinations were made on the titanium oxide trimethylsilyloxide polymers (polytrimethylsiloxanotitanoxanes) obtained by thermal disproportionation. Structures have been suggested for the polymers on the basis of the variation of number-average degree of polymerization with the degree of hydrolysis.

METAL OXIDE ALKOXIDE POLYMERS: PART II. THE HYDROLYSIS OF TANTALUM PENTAETHOXIDE

1961 ◽  
Vol 39 (9) ◽  
pp. 1818-1826 ◽  
Author(s):  
D. C. Bradley ◽  
H. Holloway
Keyword(s):  
Metal Oxide ◽  
Tantalum Oxide ◽  
Structural Models ◽  
Degree Of Polymerization ◽  
Degree Of Hydrolysis ◽  
Oh Groups ◽  
Infrared Studies ◽  
Hydrolysis Of ◽  
Considerable Range ◽  
Characteristic Manner

The hydrolysis of tantalum pentaethoxide has been studied in boiling benzene and in boiling ethanol. Soluble tantalum oxide ethoxides were obtained over a considerable range of hydrolysis. Infrared studies suggest that Ta—OH groups are absent in these products. Ebulliometric studies have shown that the number-average degree of polymerization varies with the degree of hydrolysis in a characteristic manner and this has been quantitatively explained in terms of fundamental structural models based on octahedrally 6-co-ordinated tantalum.

Properties of humic and fulvic acids under the long-term use of fertilizers in a rice-wheat-cowpea system on a mollisol

2007 ◽  
Vol 55 (3) ◽  
pp. 293-298
Author(s):  
D. Das ◽  
Nand Ram
Keyword(s):  
Nutrient Management ◽  
Fulvic Acids ◽  
Oh Groups ◽  
Molecular Weights ◽  
Northern India ◽  
Carboxylic Groups ◽  
Long Term Experiment ◽  
C And N ◽  
Phenolic Oh Groups

The properties of humic (HA) and fulvic acids (FA) isolated from a 27-year-old long-term experiment with rice-wheat-cowpea on a Mollisol in northern India were evaluated for elemental composition and functional groups. As compared to fallow, C, H and N decreased, while O increased in the control, but the use of NPK+FYM over the years enhanced the C and N of humic substances. The carboxylic (-COOH) and phenolic-OH groups declined in the control, but improved with NPK+FYM in comparison to fallow. Carboxylic groups (-COOH) contributed about 2–3 times more in HA and 4–5 times more in FA than the respective phenolic-OH groups to the molecular weights of these fractions of soil organic matter. The results suggested the role of integrated nutrient management in maintaining active soil humus over the years.

scholarly journals Expression and Characterization of an Alginate Lyase and Its Thermostable Mutant in Pichia pastoris

Marine Drugs ◽  
2020 ◽  
Vol 18 (6) ◽  
pp. 305
Author(s):  
Suxiao Yang ◽  
Zhemin Liu ◽  
Xiaodan Fu ◽  
Changliang Zhu ◽  
Qing Kong ◽  
...  
Keyword(s):  
Pichia Pastoris ◽  
Degradation Products ◽  
Alginate Lyase ◽  
Maximal Activity ◽  
Degree Of Polymerization ◽  
Molecular Weights ◽  
Industrial Preparation ◽  
Alginate Oligosaccharides ◽  
Elimination Mechanism ◽  
G Ratio

Alginate is one of the most abundant polysaccharides in algae. Alginate lyase degrades alginate through a β-elimination mechanism to produce alginate oligosaccharides with special bioactivities. Improving enzyme activity and thermal stability can promote the application of alginate lyase in the industrial preparation of alginate oligosaccharides. In this study, the recombinant alginate lyase cAlyM and its thermostable mutant 102C300C were expressed and characterized in Pichia pastoris. The specific activities of cAlyM and 102C300C were 277.1 U/mg and 249.6 U/mg, respectively. Both enzymes showed maximal activity at 50 °C and pH 8.0 and polyG preference. The half-life values of 102C300C at 45 °C and 50 °C were 2.6 times and 11.7 times the values of cAlyM, respectively. The degradation products of 102C300C with a lower degree of polymerization contained more guluronate. The oligosaccharides with a polymerization degree of 2–4 were the final hydrolytic products. Therefore, 102C300C is potentially valuable in the production of alginate oligosaccharides with specific M/G ratio and molecular weights.

THE VISCOSITY – MOLECULAR WEIGHT RELATION FOR POLY-levo-2,3-BUTANEDIYL o-PHTHALATE

1948 ◽  
Vol 26b (12) ◽  
pp. 783-797
Author(s):  
R. W. Watson ◽  
N. H. Grace
Keyword(s):  
Molecular Weight ◽  
High Purity ◽  
Molecular Orientation ◽  
Degree Of Polymerization ◽  
Solution Viscosity ◽  
Dilute Solution ◽  
Molecular Weights ◽  
Complex Relation ◽  
End Group ◽  
Long Chain

The inherent viscosities of dilute solutions of acidic polyesters of high purity have been compared with number average molecular weights accurately determined by end-group titration. For unfractionated resins with a degree of polymerization from 2 to 11 [Formula: see text] the viscosity – molecular weight relation is linear in chloroform at 25 °C. Where [Formula: see text], K = 1.923 × 10−5 and β = 0.0176. For fractionated polyesters from DP 5 to 8, K = 1.959 × 10−6 and β = 0.0161. For unfractionated resins with a DP > 11, molecular weights increase more rapidly than inherent viscosities. Above [Formula: see text] for fractionated resins linearity is resumed, and the slope increases. Several attempts have been made to explain this complex relation. Apparently the short chains remain linear, and the formation of anisotropic fibers at a DP close to 100 establishes a degree of molecular orientation in the long-chain superpolyesters. Isomerization of levo-diol to the diastereoisomer during polycondensation is without effect on the dilute solution viscosity of the resulting resin. Preferential degradation of the longer chains is assumed to be partially responsible for the decreasing slope from DP 11 to 65. As yet it has not been possible to assess the roles played by changes in size distribution, and variation in solvation with increasing chain length, but the data point to a curved viscosity – molecular weight relation in chloroform at 25 °C.

METAL OXIDE ALKOXIDE POLYMERS: PART I. THE HYDROLYSIS OF SOME PRIMARY ALKOXIDES OF ZIRCONIUM

1961 ◽  
Vol 39 (7) ◽  
pp. 1434-1443 ◽  
Author(s):  
D. C. Bradley ◽  
D. G. Carter
Keyword(s):  
Metal Oxide ◽  
Zirconium Oxide ◽  
Structural Models ◽  
Degree Of Polymerization ◽  
Degree Of Hydrolysis ◽  
Zirconium Alkoxides ◽  
Hydrolysis Of

Ebulliometric studies have been made on the hydrolysis of some zirconium alkoxides, Zr(OR)4 where R = Et, Prn, Bui, and Bun. The variation of the degree of polymerization of the zirconium oxide alkoxides so produced was determined as a function of the degree of hydrolysis. The results are interpreted in terms of structural models based on octahedrally 6-co-ordinated zirconium.

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:

Cleavage of models for RNA mediated by a diZn(II) complex of bis[1,4-N1,N1′(1,5,9-triazacyclododecanyl)]butane in methanol and ethanol

2009 ◽  
Vol 87 (5) ◽  
pp. 640-649 ◽  
Author(s):  
C. Tony Liu ◽  
Stephanie A. Melnychuk ◽  
Chaomin Liu ◽  
Alexei A. Neverov ◽  
R. Stan Brown
Keyword(s):  
Transition State ◽  
Linear Dependence ◽  
Catalyst Concentration ◽  
Active Form ◽  
Catalytic Efficiency ◽  
Saturation Binding ◽  
Controlled Conditions ◽  
Versus Complex ◽  
Leaving Groups ◽  
Ph Controlled

The cleavage of seven RNA model 2-hydroxypropyl aryl phosphates (1) catalyzed by a dinuclear Zn(II) complex of bis[1,4-N1,N1′(1,5,9-triazacyclododecanyl)]butane (4) was studied in methanol and ethanol at 25 °C under pH controlled conditions. The results are compared with what was reported earlier for the dinuclear Zn(II) complex of the lower homologue bis[1,3-N1,N1′(1,5,9-triazacyclododecanyl)]propane (3). In methanol, the higher homologue exhibits saturation binding with substrates having poor aryloxy leaving groups. With good leaving groups there is an observed linear dependence of kobs versus complex concentration without saturation binding over the catalyst concentration range investigated. In ethanol, strong saturation binding between the active form of the catalyst ((RO–):Zn(II)2:4) and all substrates is observed, the results observed in both solvents being similar to what was reported for the lower (RO–):Zn(II)2:3 homologue. Energetics calculations are presented for the (RO–):Zn(II)2:4-catalyzed cleavage of each substrate in both solvents to assess the catalytic efficiency via the ΔΔG‡ for catalyst binding a transition state comprising [RO–:1]‡ or its kinetic equivalent.

scholarly journals Calcination on Ca-Mg-Al Hydrotalcite from Brine Water and Its Characterization

2017 ◽  
Vol 13 (2) ◽  
Author(s):  
Eddy Heraldy ◽  
Khoirina Dwi Nugrahaningtyas ◽  
Heriyanto Heriyanto
Keyword(s):  
Thermal Analysis ◽  
Particle Size ◽  
Particle Size Distribution ◽  
Metal Oxide ◽  
Size Distribution ◽  
Hydroxyl Groups ◽  
Absorption Region ◽  
Oh Groups ◽  
Wavenumber Region ◽  
Calcination Treatment

<p>The study of calcination treatment at 450°C on Ca-Mg-Al-hydrotalcite from brine water has been investigated. Characterization by XRD shows that Ca-Mg-Al hydrotalcite compound has found hydrotalcite phase and another phase such as Mg(OH)<sub>2</sub>, Al(OH)<sub>3</sub> and CaCO<sub>3</sub>. These results are confirmed by the presence of hydroxyl groups, M-O and M-OH groups (M is Mg, Ca and Al) at wavenumber region around 3464.35 cm<sup>-1</sup>, 447.50 cm<sup>-1</sup> and 531.41 cm<sup>-1</sup>. The calcination effect on Ca-Mg-Al hydrotalcite compounds at 450ºC being led to changes in structure become an metal oxide such as MgO, CaO, Al<sub>2</sub>O<sub>3</sub>, MgAl<sub>2</sub>O<sub>4</sub> and CaCO<sub>3</sub>. These results are confirmed from decreasing on the absorption peak of M-OH group at wavenumbers region around 531.41 cm<sup>-1</sup> and 786.99 cm<sup>-1</sup> and widening of the absorption region at 500-900 cm<sup>-1</sup>. Consequently, the calcination treatment successfully increased the surface area of Ca-Mg-Al hydrotalcite compounds from 97.4 m<sup>2</sup>/g to 156.826 m<sup>2</sup>/g. Morphology of Ca-Mg-Al hydrotalcite changes the shape from a big to be small shape and the particle size distribution of 0-0.25 μm into 0-1 μm. Thermal analysis showed changes in the structure of hydrotalcite into oxide begins at a temperature of 265°C and started to become oxide completely after the temperature reaches 428°C.</p>

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