Polymer, amorphous branched

Agarwal, S. and Speyere, C. (2010) Degradable blends of semi-crystalline and amorphous branched poly(caprolactone) effect of microstructure on blend properties. Polymer, 51 (5), 1024-1032. 

Similarly, a study of ethyl-branched ADMET PE has also been reported [139]. This work showed that these polymers favored branch inclusion, resulting in a crystal structure similar to that obtained for the precisely methyl-branched ADMET polymers. This crystallization behavior, however, was dependent on branch concentration. When the branch content was 111 ethyl branches per 1000 carbons, the resulting polymer was amorphous, indicating that the steric demands of the ethyl branches precluded their participation in crystallization. Conversely, ethyl branch contents of 50-60 branches per 1000 carbons resulted in polymers able to include the ethyl branch defects in the crystal lattice, presumably due to the presence of kink defects able to accommodate the ethyl branches. 

One of the most important structural elements of polymers is the nature of the branches or side chains. This subject is particularly important for crystalline polymers, because branches disrupt the crystalline order. It is important not only to establish the number and distribution of branches along the chain but also to determine their distribution between amorphous, interfacial, and crystalline phases and to... 

Irregularities such as branch points, comonomer units, and cross-links lead to amorphous polymers. They do not have true melting points but instead have glass transition temperatures at which the rigid and glasslike material becomes a viscous liquid as the temperature is raised. 

Most Kaminsky catalysts contain only one type of active center. They produce ethylene—a-olefin copolymers with uniform compositional distributions and quite narrow MWDs which, at their limit, can be characterized by M.Jratios of about 2.0 and MFR of about 15. These features of the catalysts determine their first appHcations in the specialty resin area, to be used in the synthesis of either uniformly branched VLDPE resins or completely amorphous PE plastomers. Kaminsky catalysts have been gradually replacing Ziegler catalysts in the manufacture of certain commodity LLDPE products. They also faciUtate the copolymerization of ethylene with cycHc dienes such as cyclopentene and norhornene (33,34). These copolymers are compositionaHy uniform and can be used as LLDPE resins with special properties. Ethylene—norhornene copolymers are resistant to chemicals and heat, have high glass transitions, and very high transparency which makes them suitable for polymer optical fibers (34). 

The ultraphosphates are situated between P O q and the metaphosphates. These comparatively Htde-known, highly cross-linked polymers contain at least some of the phosphoms atoms as triply coimected branching points. This stmctural feature is quite unstable toward hydrolysis. Ultraphosphates undergo rapid decomposition upon dissolution. In amorphous ultraphosphates, the cross-linking is presumably scattered randomly throughout the stmctural matrix in contrast, crystalline ultraphosphates have a regular pattern. 

Abstract This chapter gives an overview of the research on the self-assembly of amorphous block copolymers at different levels of hierarchy. Besides the influence of composition and topology on the morphologies of block copolymers with linear, cyclic and branched topologies blends of block copolymers with low molecular weight components, other polymers or block copolymers and nanoparticles will also be presented. 

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