Ethene−Norbornene Copolymerization with Homogeneous Metallocene and Half-Sandwich Catalysts:  Kinetics and Relationships between Catalyst Structure and Polymer Structure. 4. Development of Molecular Weights

1998 ◽  
Vol 31 (15) ◽  
pp. 4684-4686 ◽  
Author(s):  
Dieter Ruchatz ◽  
Gerhard Fink
Keyword(s):  
Polymer Structure ◽  
Catalyst Structure ◽  
Molecular Weights ◽  
Half Sandwich

Statistical Treatments of Rubber Structure

1960 ◽  
Vol 33 (5) ◽  
pp. 1201-1217 ◽  
Author(s):  
J. Scanlan ◽  
W. F. Watson
Keyword(s):  
Molecular Weight ◽  
Experimental Testing ◽  
Polymer Structure ◽  
Polymer Chains ◽  
Molecular Weights ◽  
Average Value ◽  
Physical Form ◽  
The Subject ◽  
Branched Structures ◽  
Mathematical Analyses

Abstract Chemical reactions are random in nature and can therefore be subjected to mathematical analyses based on probability theory. This is a particularly necessary approach to polymer structure in which the effect of chance inherent in the reactions is preserved in physical form and therefore much attention has been given to deductions from such treatments. It is the purpose of this paper to review the results of those investigations which have particular application to rubbery high polymers. Some emphasis will be given to the authors' view that experimental testing of the derived expressions is still far from being satisfactory and that the subject in spite of the effort expended is still only at its beginning. Consideration of details of polymer structure is not merely an academic exercise. The properties of raw rubbers are highly dependent on polymer chain length and for many important ones such as viscosity, either in solution or in the melt, the dependence is not simply linear. Unless linear dependence on the number of molecules and their size does apply, an average value of molecular weight is insufficient to characterize a rubber sample in respect of the property considered and further knowledge of the distribution of molecular weights among the rubber molecules is required. The properties of rubbers are also markedly influenced by the occurrence of branching in the polymer chains; the insolubility and elasticity conferred by vulcanization are the results of the formation of complex branched structures which have been the subjects for statistical treatments.

Synthesis of Poly(Dinaphthylene Ether) by Oxidative Coupling Polymerization of Di(1-Naphthoxy)Pentane Using Cobalt (III) Acetylacetonate

1998 ◽  
Vol 10 (3) ◽  
pp. 241-247
Author(s):  
Takashi Okada ◽  
Satoru Amou ◽  
Osamu Haba ◽  
Mitsuru Ueda
Keyword(s):  
Oxidative Coupling ◽  
Room Temperature ◽  
Methanesulfonic Acid ◽  
Polymer Structure ◽  
Naphthalene Ring ◽  
Molecular Weights ◽  
Polymer Formation ◽  
Coupling Polymerization ◽  
C Nmr ◽  
Model Reactions

Poly(dinaphthylene ether) was prepared by oxidative coupling polymerization of 1,5-di(naphthoxy)pentane. Polymerizations were conducted in 1,2-dichloroethane in the presence of cobalt (III) acetylacetonate and methanesulfonic acid at room temperature and produced poly(dinaphthylene ether)s with number-average molecular weights up to 10 000. The polymer structure was characterized by 1H and 13C-NMR spectroscopies, and selective coupling was found to occur at the C-4 position of the 1-substituted naphthalene ring. The model reactions were studied to demonstrate the feasibility of polymer formation.

scholarly journals Efficient and selective degradation of polyethylenes into liquid fuels and waxes under mild conditions

2016 ◽  
Vol 2 (6) ◽  
pp. e1501591 ◽  
Author(s):  
Xiangqing Jia ◽  
Chuan Qin ◽  
Tobias Friedberger ◽  
Zhibin Guan ◽  
Zheng Huang
Keyword(s):  
Product Distribution ◽  
Liquid Fuels ◽  
Catalyst Structure ◽  
Molecular Weights ◽  
Selective Degradation ◽  
Mild Conditions ◽  
Cross Metathesis ◽  
Alkane Metathesis ◽  
Chemical Inertness ◽  
Energy Processes

Polyethylene (PE) is the largest-volume synthetic polymer, and its chemical inertness makes its degradation by low-energy processes a challenging problem. We report a tandem catalytic cross alkane metathesis method for highly efficient degradation of polyethylenes under mild conditions. With the use of widely available, low-value, short alkanes (for example, petroleum ethers) as cross metathesis partners, different types of polyethylenes with various molecular weights undergo complete conversion into useful liquid fuels and waxes. This method shows excellent selectivity for linear alkane formation, and the degradation product distribution (liquid fuels versus waxes) can be controlled by the catalyst structure and reaction time. In addition, the catalysts are compatible with various polyolefin additives; therefore, common plastic wastes, such as postconsumer polyethylene bottles, bags, and films could be converted into valuable chemical feedstocks without any pretreatment.

Synthesis,Characterization and Flocculability of a Poly (p-Ethylstyrene -Acrylamide- Propenohydroxamic Acid)

2013 ◽  
Vol 634-638 ◽  
pp. 2065-2071
Author(s):  
Feng Chen ◽  
Zi Qiang Chen ◽  
Lei Wang ◽  
Xu Shao ◽  
Hao Yu Zhao
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Hydroxamic Acid ◽  
Polymer Structure ◽  
Dispersed Phase ◽  
Microemulsion System ◽  
Molecular Weights ◽  
Ft Ir ◽  
Hydroxylamine Sulfate ◽  
Settling Rates

A novel poly (p-ethylstyrene-acrylamide-propenohydroxamic acid) was synthesized. Copolymerization of acrylamide and p-ethylstyrene was carried out at 30°C in a microemulsion system, in which AM aqueous solution was the continue phase and p-ethylstyrene was the dispersed phase using ST-80 as surfactants respectively. Polymers of hydroxamic functions were prepared with hydroxylamine sulfate at temperatures from 60 °C-85°C and pH=10. The molecular weights were measured through the viscose method and the copolymers were characterized by FT-IR, UV and DSC. The effect of the polymer structure on the process of red mud setting was investigated. The results show that the optimal experimental condition is the hydroxamic acid flocculants contains 10.5% p-ethylphenylethylene and the molecular weight of synthesized product is 11×106; The polymer provides dramatically lower overflow solids at higher mud settling rates than hydroxamic acid flocculant.

Elastomeric Poly(propylene): Influence of Catalyst Structure and Polymerization Conditions on Polymer Structure and Properties

1995 ◽  
Vol 28 (11) ◽  
pp. 3771-3778 ◽  
Author(s):  
William J. Gauthier ◽  
John F. Corrigan ◽  
Nicholas J. Taylor ◽  
Scott Collins
Keyword(s):  
Polymer Structure ◽  
Structure And Properties ◽  
Catalyst Structure ◽  
Poly Propylene ◽  
Polymerization Conditions

scholarly journals Nanofibers for drug delivery – incorporation and release of model molecules, influence of molecular weight and polymer structure

2015 ◽  
Vol 6 ◽  
pp. 1939-1945 ◽  
Author(s):  
Jakub Hrib ◽  
Jakub Sirc ◽  
Radka Hobzova ◽  
Zuzana Hampejsova ◽  
Zuzana Bosakova ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Polyvinyl Alcohol ◽  
Polymer Structure ◽  
Release Profile ◽  
Polyethylene Glycols ◽  
Aqueous Environment ◽  
Molecular Weights ◽  
Molecular Length ◽  
Pharmacologically Active ◽  
Pharmacologically Active Compounds

Nanofibers were prepared from polycaprolactone, polylactide and polyvinyl alcohol using NanospiderTM technology. Polyethylene glycols with molecular weights of 2 000, 6 000, 10 000 and 20 000 g/mol, which can be used to moderate the release profile of incorporated pharmacologically active compounds, served as model molecules. They were terminated by aromatic isocyanate and incorporated into the nanofibers. The release of these molecules into an aqueous environment was investigated. The influences of the molecular length and chemical composition of the nanofibers on the release rate and the amount of released polyethylene glycols were evaluated. Longer molecules released faster, as evidenced by a significantly higher amount of released molecules after 72 hours. However, the influence of the chemical composition of nanofibers was even more distinct – the highest amount of polyethylene glycol molecules released from polyvinyl alcohol nanofibers, the lowest amount from polylactide nanofibers.

scholarly journals Synthesis of polystyrene-block-poly(iso-butyl vinyl ether) by dinuclear half-metallocene catalyst and atom transfer radical polymerization

2015 ◽  
Vol 18 (3) ◽  
pp. 189-199
Author(s):  
Thanh Thi Le Nguyen ◽  
Nhon Thi Le Nguyen
Keyword(s):  
Atom Transfer Radical Polymerization ◽  
Radical Polymerization ◽  
Vinyl Ether ◽  
Metallocene Catalyst ◽  
Gel Permeation Chromatography ◽  
Atom Transfer ◽  
Narrow Molecular Weight Distribution ◽  
Molecular Weights ◽  
Gel Permeation ◽  
Half Sandwich

The synthesis of polystyrene-block-poly(iso-butyl vinyl ether) by using the combination of metallocene catalyst and atom transfer radical polymerization (ATRP) has been tried. This synthetic method takes advantages of both metallocene catalyst to form stereoregular polymer with high activity and ATRP with the controlled molecular weights and low polydispersity. The recent dinuclear half-sandwich complexes of titanium with xylene bridge, [Ti(η5-cyclopentadienyl)Cl2L]2-ortho, meta-[CH2-C6H4-CH2] (L = Cl, L = O-2,6-iPr2C6H3 ) were successfully synthesized. These catalysts were characterized by 1H NMR, 13C NMR and elemental analysis. Copolymers have been characterized by using gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR). The collected copolymers have got narrow molecular weight distribution (≤1.8) and the improvement of stereoregularity (racemo dyads, r, are from 45 % to 56 %).

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