Controlled polymer structures synthesis

With the details associated with ADMET chemistry reasonably well understood, we have embarked on a study of the synthesis of well-controlled polymer structures via metathesis polycondensation chemistry [37]. A series of well-defined polyolefins have been designed to model the crystallization behavior of polyethylene and its related copolymers, including new materials synthesized by metallocene-based catalysts. This synthesis concept has been reduced to practice, and polymers that will aid in the understanding of branching within polyethylene itself have been produced. 

Kee RA, Gauthier M, Tomalia DA. Semi-controlled dendritic structure synthesis. In Tomalia DA, Frechet JMJ, editors. Dendrimers and Other Dendritic Polymers. West Sussex Wiley 2001. p 209. 

Only few of the metal-catalyzed reactions allow the synthesis of well-controlled polymer structures. Thus, in the following, only two recent developments leading to rather defined polymer architectures will be addressed functional and branched polyolefins by late transition metal catalysis and ROMP. 

Kee, R.A., Gauthier, M., and Tomalia, D.A. (2001) Semi-controlled dendritic structure synthesis, in Dendrimers and Other Dendritic Polymers (eds. J.M.J. Frechet and D.A. Tomalia) Wiley, New York, pp. 209-236. 

Gel electrophoresis is widely used in the routine analysis and separation of many well-known biopolymers such as proteins or nucleic acids. Little has been reported concerning the use of this methodology for the analysis of synthetic polymers, undoubtedly since in many cases these polymers are not soluble in aqueous solution - a medium normally used for electrophoresis. Even for those water-soluble synthetic polymers, the broad molecular weight dispersities usually associated with traditional polymers generally preclude the use of electrophoretic methods. Dendrimers, however, especially those constructed using semi-controlled or controlled structure synthesis (Chapters 8 and 9), possess narrow molecular weight distribution and those that are sufficiently water solubile, usually are ideal analytes for electrophoretic methods. More specifically, poly(amidoamine) (PAMAM) and related dendrimers have been proven amendable to gel electrophoresis, as will be discussed in this chapter. 

Polymer hypothesis Stereoregulation of polymer structure Organization of polymer chains Synthesis on a solid matrix Polymer structure and control at interfaces Conductive polymers... 

Enzymatic polymerizations have been established as a promising and versatile technique in the synthetic toolbox of polymer chemists. The applicability of this technique for homo- and copolymerizations has been known for some time. With the increasing number of reports on the synthesis of more complex structures like block copolymers, graft copolymers, chiral (co)polymers, and chiral crosslinked nanoparticles, its potential further increases. Although not a controlled polymerization technique itself, clever reaction design and integration with other polymerization techniques like controlled radical polymerization allows the procurement of well-defined polymer structures. Specific unique attributes of the enzyme can be applied... 

In controlled polymer synthesis, in addition, it is particularly important that the control herein implies not only the simple regulation of molecular weights, MWD, and other structural factors but also the precise introduction of functional groups into specific positions of polymers with well-defined architectures. Namely, the control of one or more of these structural factors, then, leads to a variety of polymers of synthetic interest, as some of them illustrated schematically in Fig. 2 ... 

This chapter presents an updated overview of the current status of the controlled polymer syntheses via the modem generation of cationic polymerizations that are mostly living or controlled what and how one can design and eventually synthesize novel polymers with well-defined structures and functionalities. Thus, the following sections are devoted to each of these classes of polymers (Fig. 2), with emphasis on the general methodologies and specific examples. The last section (Section VII) briefly covers the experimental procedures in living cationic polymerization and related polymer synthesis. 

Electrochemical polymerisation produces films on an electrode surface.. Under controlled conditions uniform films up to a few mm thick, which carl be removed from the electrode for subsequent study, can be prepared. Physical properties can be modified by choice of the counterions (dopants) included in the film during growth. It is, however, more difficult to control chain structure and crosslinking than in chemical methods. Electrochemically produced polymers are, therefore, less well characterised than the best directly-synthesised polymers. While this is less satisfactory for fundamental investigations, it is of less concern for applications such as battery electrodes, artificial muscles and drug release agents. The two main approaches, direct-synthesis and electrochemical, are described in the following two sections. 

The only way to control the polymer structure properly during its synthesis is by a living process. In conventional FRP, in fact, bimolecular combination limits the chain lifetime to a small fraction of the entire process time and, therefore, changes in the operating conditions (monomer concentration and... 

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