Polymer, branched Crosslinked

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. 

A microgel is an intramolecularly crosslinked macromolecule which is dispersed in normal or colloidal solutions, in which, depending on the degree of crosslinking and on the nature of the solvent, it is more or less swollen. Besides linear and branched macromolecules and crosslinked polymers, intramolecularly crosslinked macromolecules may be considered as a fourth class of macromolecules. 

That branching/crosslinking occured with HFB was evidenced by rapid gelation in some runs, and by partial insolubility of some isolated polymers. Control experiments, runs without catalyst, were carried out to demonstrate the catalytic nature of the reaction for each... 

For each of the following reactions system indicate whether the product is a linear, branched, crosslinked, or hyperbranched polymer. 

Polymer glasses are formed best when the macromolecular chains are irregular in structure (atactic, branched, crosslinked) so that crystallization is prevented. Regular (isotactic, syndiotactic unbranched) polymer chains form glasses only if they are cooled down so fast that crystallization is prevented such a quenching procedure freezes the material in the glassy state even if the polymer is able to crystallize. 

The concentration of modifier will tend to diminish during the reaction, and the more reactive the modifier, the more serious is the effect likely to be. An extension of the Flory treatment of crosslinking to take into account the presence of modifier demonstrates the point. When branches arise by transfer to polymer and crosslinks by the subsequent coupling of branched radicals, it is easy enough to show that the rate of formation of crosslinks, X, as a function of conversion is ... 

Molecular architecture Linear polymers Branched polymers Crosslinked network... 

Polymer product quality control The molecular architecture of a polymer is very sensitive to reaction environment. The actual customer specifications are often represented by nonmolecu-lar parameters (e.g., tensile strength, impact strength, color, crack resistance, thermal stability, etc.) that must be somehow related to fundamental polymer properties such as molecular weight distribution, composition, composition distribution, branching, crosslinking, etc. Many of these properties are influenced by more than one reaction or process variable and hence, one needs to understand complex and nonlinear relations between reaction variables and fundamental polymer properties. The lack of online... 

Polymer - Polymers are high molecular weight substances with molecules resembling linear, branched, crosslinked, or otherwise shaped chains consisting of repeating molecular groups. Synthetic polymers are prepared by polymeriza-... 

Semi-IPN. These are compositions in which one or more polymers are crosslinked, and one or more polymers are linear or branched. 

CLEAR resins differ from the standard crosslinked polymers by the incorporation of branched crosslinking agents such as 1 and 6. The amino groups present in monomers 2 and 3 constitute the attachment points for potential linker groups. CLEAR resins show excellent... 

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