Polymer backbones, living polymerization

Hawker et al. 2001 Hawker and Wooley 2005). Recent developments in living radical polymerization allow the preparation of structurally well-defined block copolymers with low polydispersity. These polymerization methods include atom transfer free radical polymerization (Coessens et al. 2001), nitroxide-mediated polymerization (Hawker et al. 2001), and reversible addition fragmentation chain transfer polymerization (Chiefari et al. 1998). In addition to their ease of use, these approaches are generally more tolerant of various functionalities than anionic polymerization. However, direct polymerization of functional monomers is still problematic because of changes in the polymerization parameters upon monomer modification. As an alternative, functionalities can be incorporated into well-defined polymer backbones after polymerization by coupling a side chain modifier with tethered reactive sites (Shenhar et al. 2004 Carroll et al. 2005 Malkoch et al. 2005). The modification step requires a clean (i.e., free from side products) and quantitative reaction so that each site has the desired chemical structures. Otherwise it affords poor reproducibility of performance between different batches. 

Anionic Coupling or Attachment. Graft polymers have also been made by the reaction of living polymeric lithium salts at pendant functional groups on a polymer backbone, for excunple ... 

Living ring opening metathesis polymerization methods (ROMP) were first employed to synthesize LC-coil diblock copolymers by Komiya and Shrock [80] in 1993. The structure of their polymer system is shown in Scheme 7D. Recent work from Grubbs group also used a novel ruthenium catalyst which can tolerate more functional groups [81] to synthesize well-defined LC-coil block copolymers [82]. The ROMP polymer backbone can be hydrogenated to create saturated structure to improve its stability. 

When vinyl chloride is polymerized in solution there is no autoacceleration. Also, a major feature of vinyl chloride free-radical pohmierization is chain transferring to monomer. This is supported by experimental evidence. In addition, the growing radical chains can terminate by chain transferring to dead polymer molecules. The propagations then proceed from the polymer backbone. Such new growth radicals, however, are probably short-lived as they are destroyed by transfer to monomer. ... 

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