Polymerization methods Stille coupling

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. 

Terminal ring functionalization has been explored as a route to block copolymer synthesis. The Stille coupling approach affords Br and RsSn termini on an isolable product. Iraqi and Barker isolated a low-A/ fraction (DP 14) then homo-cross-coupled to increase Af (DP ra 28), thus demonstrating telechelic utility [43]. The nature of the nickel-initiated cross-coupling polymerization (GRIM method) allows chain extension from the quasi-living end until the reaction is terminated. Controlled blocks of HT-PHT with HT-PDDT were prepared by changing the monomer [63]. 

Stationary Polymerization Methods. The determination of the kinetic rate coefficients and p in their coupled form k /kt has long proceeded via measurement of the rate of polymerization and the calculation of the kp/kt via equation 56. With the advent of pulsed laser techniques that allow to obtain much more accurate and detailed information about the kinetic rate coefficients (such as chain length dependencies), these techniques became less important. Nevertheless, measurements of the rate of polymerization are still widely performed and are... 

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