Synthesis, graft copolymer polymer transfer

It is evident that the values of the transfer constants are dependent on the nature both of the attacking radicals and of the transfer agent itself, and that similar effects should be expected during the synthesis of graft copolymers by chain transfer methods. For example, with respect to toluene the chain transfer constant is a little greater for methyl methacrylate radicals than for styrene radicals on the contrary, with respect to halogenated solvents (CC14) the polystyrene radical is much more effective in the removal of a chlorine atom. Vinyl acetate chains are far more effective than either of the other two polymer radicals. 

Another consequence of the absence of sponataneous transfer and termination reactions is that the polymer chains formed remain living 3), i.e. they carry at the chain end a metal-organic site able to give further reactions. Block copolymer synthesis is probably the major application 12 14), but the preparation of co-functional polymers, some chain extension processes, and the grafting onto reactions arise also directly from the long life time of the active sites. 

The isopropyl group discourages P-H transfer, leading to the exclusive formation of Al-PEs. The Al-PEs can be readily transformed to a variety of functionalized PEs and to PE-based and polar polymer-based block and graft copolymers, using established methods. The selective synthesis of vinyl- and Al-terminated PEs with Zr-FI catalysts shows the critical importance of the substituent on the imine-N for polymerization catalysis. 

Nakagawa, Y., Miller, P. J., and Matyjaszewski, K. (1998). Development of novel attachable initiators for atom transfer radical polymerization. Synthesis of block and graft copolymers from poly(dimethylsiloxane) macroinitiators. Polymer, 39(21) 5163-5170. 

Pan, Q., et al. (1999). Synthesis and characterization of block-graft copolymers composed of poly(styrene-b-ethylene-co-propylene) and poly(ethyl methacrylate) by atom transfer radical pol5merization. J. Polym. ScL, Part A Polym. Chem., 57(15) 2699-2702. 

Ckinventional free-radical polymerization, either by so-called graffing-ffom or grafting-onto techniques are the oldest and were the most widely used procedures for the synthesis of graft copolymers because they are very simple [2 ]. In fact, graft copolymers can easily be obtained by polymerization of a monomer A in presence of a preformed polymer B acting, either as a chain-transfer agent or as a macroinitiator. However, these procedures usually... 

Because such polyether spacer polymers are also of interest in other fields of polymer-supported immobilization, the first reports published on the synthesis of polystyrene graft copolymers date back to almost one decade agp [111,112]. In fact, these graft supports have been applied successfidly in f ds where insoluble polymers with homogeneous phase reacticais are advantageous, e.g., for phase-transfer reactions [113-116]. 

It is feasible to use functionalized thiols as transfer agents to prepare end-functional polymers. Such materials have successfully been used in the synthesis of block and graft copolymers. 

The term living polymerization describes any chain growth polymerization that proceeds in the absence of chain termination and chain transfer reactions. This condition of uninterrupted chain growth confers great synthetic utility, enabling the synthesis of sophisticated macromolecules such as block copolymers, star polymers, end-functional (telechelic) polymers, uniform graft copolymers, etc. 

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