Polymer high-molecular mass

FI and FD are mild or soft methods of ionization that produce abundant molecular or quasi-molecular positive or negative ions from a very wide range of substances. In the FD mode, it is particularly useful for high-molecular-mass and/or thermally labile substances such as polymers, peptides, and carbohydrates. 

Laser desorption is particularly good for producing ions from analytically difficult materials. For example, lasers can be used with bone, ceramics, high-molecular-mass natural and synthetic polymers, and rock or metal specimens. Generally, few fragment ions are formed. 

Lasers have advanced the analytical use of mass spectrometers to characterise additives in polymers, and routine application of MALDI is no longer limited to high molecular masses only. MALDI can now clearly produce isotopically resolved mass spectra of small molecules (<800 Da) in an L-ToF instrument, which can be used successfully for the characterisation of molecules of different chemical classes. High mass resolution with an improvement of mass accuracy to... 

From this equation it can first be deduced that the successful synthesis of high polymers by step polymerisation (i.e., polymers exhibiting molecular mass sufficiently high to be useful for technological application) requires very high conversion levels. 

In polymer science and technology, linear, branched and crosslinked structures are usually distinguished. For crosslinked polymers, insolubility and lack of fusibility are considered as characteristic properties. However, insoluble polymers are not necessarily covalently crosslinked because insolubility and infusibility may be also caused by extremely high molecular masses, strong inter-molecular interaction via secondary valency forces or by the lack of suitable solvents. For a long time, insolubility was the major obstacle for characterization of crosslinked polymers because it excluded analytical methods applicable to linear and branched macromolecules. In particular, the most important structural characteristic of crosslinked polymers, the crosslink density, could mostly be determined by indirect metho ds only [ 1 ], or was expressed relatively by the fraction of crosslinking monomers used in the synthesis. 

After activation with MAO (molar ratios [Al] [Zr] = 1000) the polymerization of ethylene has been successfully carried out using the zirconocene functionalized dendrimer at 40 bar ethylene pressure and 70 °C. We obtained high activity and productivity values for the ethylene polymerization and polymers with very high molecular masses in the range of 2 x 10 g/mol. The polydispersity of the polymer is quite low (3.0) indicating the single site character of the catalytically active species. Optimization of this system and study of the mechanism are stiU under investigation. Nevertheless, these preliminary results reveal the suitability of polyphenylene dendrimers as supports for zirconocene catalysts. 

This type of polymerisation generally involves a repetitive condensation reaction between two bt-functtonal monomers. These polycondensatton reacttons may resutt In the toss of some simple molecules as water, alcohol, etc., and lead to the formation of high molecular mass condensation polymers. 

Polymers are defined as high molecular mass macromolecules, which consist of repeating structural units derived from the corresponding monomers. These polymers may be of natural or synthetic origin and are classified In a number of ways. 

Polymer is a high molecular mass macromolecule consisting of repeating structural units derived from monomers. 

Natural polymers are high molecular mass macromolecules and are found in plants and animals. The examples are proteins and nucleic acids. 

Synthetic polymers are man-made high molecular mass macromolecules. TTiese include synthetic plastics, fibres and rubbers. The two specific examples are polythene and dacron. 

Polymerisation is a process of formation of a high molecular mass polymer from one or more monomers by linking together of repeating structural units with covalent bonds. 

This allows branching of the polymer. Monomers of other chain lengths as well as aromatic components related to lignin are also present and polymerized into a high molecular mass branched structure. Suberin is a more complex ligninlike polymer with a high content of phenolic constituents135 such as vanillin (Fig. 25-8). 

One of the main peculiarities of thermotropic LC polymers is related to the high molecular mass of polymers themselves, which implies high viscosity of polymeric mesophases41 exceeding the viscosity of corresponding low-molecular liquid... 

In the processing of plastic masses the destruction is traditionally considered as a negative factor deteriorating physical and mechanical properties of products and manufacturers try to avoid it in every possible way. Mechanical destruction of molten polymers takes place, primarily, under the action of shear strains effectuating the tension of macromolecules 65-661 in this case, molecules with a high molecular mass... 

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