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.

Structural aspects of the hydrolysis products of metal alkoxides and metal trialkylsilyloxides

1969 ◽  
Vol 47 (22) ◽  
pp. 4101-4111 ◽  
Author(s):  
J. W. Lorimer ◽  
D. E. G. Jones
Keyword(s):  
Metal Oxide ◽  
Complex Structure ◽  
Theoretical Models ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Degree Of Hydrolysis ◽  
Special Cases ◽  
Plausible Mechanism ◽  
Branched Chains ◽  
Structural Aspects

The average degree of polymerization [Formula: see text] depends on the average degree of hydrolysis [Formula: see text] as[Formula: see text] over a large range of [Formula: see text] for all metal oxide alkoxides and oxide trialkylsilyloxides that have been formed by hydrolysis and examined in solution. A number of general theoretical models are developed which permit quantitative interpretation of the parameters a and b. Mixtures of linear or branched chains in proportions governed wholly or partly by the degree of polymerization of the unhydrolyzed alkoxide can explain all the data on oxide alkoxides in solution in their corresponding alcohol, and the model leads to a plausible mechanism for disproportionation. Similar models with more complex structure can be involved in the metal oxide trialkylsilyloxides. Heterogeneity in the composition of the repeating units or in the number of metal–oxygen–metal bridges between successive repeating units can also be significant for both oxide alkoxides and oxide trialkylsilyloxides. Models involving cyclic chains are possible, but steric effects make them improbable in many cases. Mixtures of chains with equal average degrees of hydrolysis for each type of chain have been assumed in previous analyses, but are shown to be special cases of the more general model.

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.

Step-growth polymerization—basics and development of new materials

2004 ◽  
Author(s):  
Zhiqun He ◽  
Eric A . Whale
Keyword(s):  
Molecular Weight ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Chain Growth ◽  
Side Reactions ◽  
Growth Processes ◽  
Molecular Weights ◽  
Reactive Groups ◽  
Step Growth ◽  
Step Growth Polymerization

Step-growth polymerization is often referred to as condensation polymerization, since often—but by no means always—small molecules such as water are released during the formation of the polymer chains. There are a number of differences in the way polymerization occurs in step-growth polymerization compared to chain-growth processes, and these have marked practical implications. The most obvious difference is that, as the name implies, the polymer chain grows in a step-wise fashion; the initial stage of the reaction involves the conversion of monomers to dimers and from these other lower molecular weight oligomers. It is only as the reaction nears completion that significant quantities of higher molecular weight material can be formed. Thus, in order to obtain effective molecular weights, the reaction must proceed almost to completion, indeed the molecular weight (in terms of the number average degree of polymerization xn) of the polymer can be linked to the extent of reaction (p) using eqn (1). Thus, in the simplest case of a difunctional (AB) monomer, when 50% of the available groups have reacted, the number average degree of polymerization is only 2. The consequence of eqn (1) is that high molecular weights in step-growth polymerizations are associated with highly efficient reactions that do not have side-reactions. Notwithstanding this, the types of molecular weights associated with chain-growth processes are not encountered in these processes (except in the case of monomers with more than two reactive groups where hyper-branched or even cross-linked polymers are possible). There is an additional complication, namely the role of cyclization. Kricheldorf has recently shown that under perfect conditions cyclization is the ultimate fate of any polymerization reaction. Thus, under extremely high conversions the prediction given by eqn (1) would overestimate the actual molecular weights produced. Molecules that undergo step-growth polymerization must have at least two reactive functional groups. If the functionality is greater than this, for example, trifunctional, then hyperbranched polymers or even cross-linked systems can be formed. Commonly, this involves the reaction of two different reactive difunctional monomers.

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.

Molecular Weight and Dispersity Affect Chain Conformation and pH-Response in Weak Polyelectrolyte Brushes

2021 ◽  
Author(s):  
Tzu-Han Li ◽  
Megan L. Robertson ◽  
Jacinta C. Conrad
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Degree Of Polymerization ◽  
Chain Conformation ◽  
Average Degree ◽  
Polyelectrolyte Brushes ◽  
Ph Response ◽  
The Impact

The impact of brush molecular weight distribution on the conformation and response of weak polyacid brushes was investigated. We show that weight-average degree of polymerization (N_w) and dispersity (Ð) alter...

Cascade theory and the molecular weight averages of the sol fraction

1963 ◽  
Vol 272 (1348) ◽  
pp. 54-59 ◽  
Keyword(s):  
Molecular Weight ◽  
Stochastic Processes ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Branched Polymers ◽  
Cascade Theory

Gordon (1962) discussed the distribution of branched polymers in solution with the help of the cascade or branching theory of stochastic processes, and dealt both with systems of copolymers and homopolymers. The present paper is concerned primarily with the latter simpler case, and the main purpose is to use cascade theory to obtain formulae for the weight average and z-average degree of polymerization of the sol fraction .

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. 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.

Simulation and Analysis of Propylene Coordination Polymerization Process Based on Aspen (polymer) plus

2020 ◽  
Vol 42 (1) ◽  
pp. 62-62
Author(s):  
Jinjin Wang Jinjin Wang ◽  
Wangbin Chen Wangbin Chen ◽  
Manlin Zhang Manlin Zhang ◽  
Bin Pan Bin Pan ◽  
Xiaorong Wang Xiaorong Wang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Performance Index ◽  
Average Molecular Weight ◽  
Degree Of Polymerization ◽  
Average Degree ◽  
Polymerization Process ◽  
Polymerization Degree ◽  
Coordination Polymerization ◽  
Actual Production ◽  
Coordination Process

Based on the industrial conditions of coordination polymerization of polypropylene, Polymer plus was used to simulate and analyze the coordination process of propylene. The effects of the amount of propane, main catalyst (TiCl4), chain transfer agent (hydrogen), shielding gas (nitrogen), and monomer (propylene) on the number average degree of polymerization (DPN), the weight average degree of polymerization (DPW), the number average molecular weight (MWN), the weight average molecular weight (MWW), the polydispersity index (PDI), and the throughput of polypropylene were explored to guide actual production in this paper. Through analysis, the polymerization degree and molecular weight of polypropylene could be adjusted by hydrogen in actual production. The monomer (propylene) should be purified as much as possible to reduce the feed amount of propane. The increase of the propylene contributed to the molecular weight and polymerization degree of the product. The increase in the nitrogen feed amount had no effect on the product performance index. The feed amount of nitrogen could be adjusted as needed according to the actual equipment specifications. The catalyst has the greatest influence on the comprehensive performance index of the product, thus the amount of main catalyst TiCl4 must be strictly controlled.

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