Atom transfer radical polymerization experimental

Zhang H, Abeln CH, Fijten MWM, Schubert US (2006) High-throughput experimentation applied to atom-transfer radical polymerization automated optimization of the copper catalysts removal from polymers. e-Polymers... 

Zhang H, Marin V, Fijten MWM, Schubert US (2004) High-throughput experimentation in atom-transfer radical polymerization a general approach toward a directed design and understanding of optimal catalytic systems. J Polym Sci Part A Polym Chem 42 1876-1885... 

Thermoresponsive polymers based on oligo(ethylene glycol) acrylates or methacrylates can be easily prepared by atom transfer radical polymerization under straightforward experimental conditions (i.e. in bulk or in ethanol solution and in the presence of commercially available catalysts). Thus, these stimuli-responsive macromolecules can be exploited for preparing a wide range of smart advanced materials such as thermoreversible hydrogels, thermoresponsive block-copolymer micelles and switchable surfaces. Hence, some of the results... 

Atom transfer radical polymerization (ATRP) was selected as an exemplary CRP technique to systematically study the kinetics and gelation behavior during the concurrent copolymerization of monovinyl monomers and divinyl cross-linkers (Scheme 2). The effect of different parameters on the experimental gelation was studied, including the initial molar ratio of cross-linker to initiator, the concentrations of reagents, the reactivity of vinyl groups present in the cross-linker, the efficiency of initiation, and the polydispersity of primary chains. Experimental gel points based on the conversions of monomer and/or cross-linker at the moment of gelation, were determined and compared with each other in order to understand the influence of each parameter on the experimental gel points. 

The importance of radical polymerizations can be ascribed to the large variety of vinyl monomers that can be polymerized and copol erized and to the undemanding experimental conditions (7). Radical polymerizations require the absence of oxygen but can be earned out in the presence of water and other impurities. In addition, radical polymerizations are tolerant to many functional groups. Mth atom transfer radical polymerization (ATRP), it is now possible to conduct radical polymerizations in a controUed/ living fashion (2-4). Structural variables of polymeric chains such as molecular wei t, molecular weight distribution (4), copolymer composition (5-ri) and terminal functionalities can be controlled (7). Furthermore, a variety of molecular architectures can be prepared such as linear, branched and hyperbranched structures (8). 

This equation shows that the radical concentration and consequently the rate of consumption of alkene in ATRA ( aid[alkene][R ], Scheme 4) under steady state conditions are dependent only on the AIBN concentration and its decomposition and termination rate constants. In other words, radical concentration in this system should not be governed by the choice of ATRA catalyst (which regulates the equilibrium constant for atom transfer, KATRA=kJk or the initial concentrations of copper(II) species. Indeed, these predictions have been shown to be in excellent agreement with experimental observations where apparent rates of polymerization in ICAR ATRP of styrene mediated by copper(II) bromide complexes with MeeTREN, TPMA, PMDETA and dNbpy... 

In many polymerization systems the polymer molecular weight is observed to he lower than predicted on the basis of the experimentally observed extents of temtination by coupling and disproportionation. This effect is due to the premature temtination of a growing polymer by the transfer of a hydrogen or other atom or species to it from some compound present in the system—the monomer, initiator, or solvent, as the case may be. These radical displacement reactions are termed chain-transfer reactions and may be depicted as... 

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