Well-defined structure polymers

Well-defined structure polymers as new polymeric additives... 

By controlling the ligands and additives, these systems opened the way to the synthesis of a wide array of homo and block polymers of well-defined structures. Polymers with PDIs of less than 1.1 that contained a variety of functional groups were routinely prepared using these initiators. 

The development of living radical polymerization has provided the capability for the polymer chemist to synthesize a wide range of novel and well-defined structures. The transformation of this capability into commercial outcomes and novel products has only just commenced. 

Compared with the aromatic electrophilic substitution approach, the SNAr approach general requires higher reaction temperatures. The polymers generally have well-defined structures. Therefore, it is more facile to control the structures of die products. In addition, it is more tolerable to some reactive functional groups, which makes it possible to synthesize reactive-group end-capped prepolymers and functional copolymers using functional monomers. 

Reactive polymers can be synthesized by either polymerizing or copolymerizing monomers containing the desired functional groups, or performing one or more modifications on a suitable polymer to introduce the essential functionality. Polymers produced directly by polymerization of functionalized monomers have well defined structures, but the physical and mechanical properties of the... 

Anionic polymerization is a powerful method for the synthesis of polymers with a well defined structure [222]. By careful exclusion of oxygen, water and other impurities, Szwarc and coworkers were able to demonstrate the living nature of anionic polymerization [223,224]. This discovery has found a wide range of applications in the synthesis of model macromolecules over the last 40 years [225-227]. Anionic polymerization is known to be limited to monomers with electron-withdrawing substituents, such as nitrile, carboxyl, phenyl, vinyl etc. These substituents facilitate the attack of anionic species by decreasing the electron density at the double bond and stabilizing the propagating anionic chains by resonance. 

The polymer networks based on silicon are very suitable for the study of cross-linked systems because of the possibility to synthesize smaller model molecules and macromolecular networks of well defined structure. An additional advantage of silicon polymers is that the resonances arising for different structural units are usually well... 

Electrochemical synthesis utilizes the ability of a monomer to be self-coupled upon irreversible oxidation (anodic polymerization) or reduction (cathodic polymerization). While this method does not always produce materials with well-defined structures (as do the three other polymerization methods to be discussed), electropolymerization, nonetheless, is a rather convenient alternative, avoiding the need for polymer isolation and purification. Of these two routes, anodic polymerization is the most widely explored as monomers such as pyrrole and thiophene are relatively electron-rich and prone to oxidation. For this reason the anodic route will be the focus of the remainder of this presentation. 

In this article, we would like to review recent advances in polymer hybrids based on polyolefins and to classify them into four methodologies, namely, PO macroinitiator, PO macromonomer, reactive PO and living copolymerization of olefins, with their well-defined structures and applications. 

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