Radical polymerization chain length dependence

Polymeric Radicals and Chain-Length Dependent Changes in ESR Spectra... 

Table 5.1 Parameters Characterizing Chain Length Dependence of Termination Rate Coefficients in Radical Polymerization of Common Monomers 1...

Some of the issues associated with RAFT emulsion polymerization have been attributed to an effect of chain length-dependent termination.528 In conventional emulsion polymerization, most termination is between a long radical and a short radical. For RAFT polymerization at low conversion most chains are short thus the rate of termination is enhanced. Conversely, at high conversion most chains are long and the rate of termination is reduced. 

The bimolecular termination reaction in free-radical polymerization is a typical example of a diffusion controlled reaction, and is chain-length-depen-dent [282-288]. When pseudobulk kinetics appUes, the MWD formed can be approximated by that resulting from bulk polymerization, and it can be solved numerically [289-291]. As in the other extreme case where no polymer particle contains more than one radical, the so-caUed zero-one system, the bimolecular termination reactions occur immediately after the entrance of second radical, so unique features of chain-length-dependence cannot be found. Assuming that the average time interval between radical entries is the same for all particles and that the weight contribution from ohgomeric chains formed... 

Computational Aspects of Free Radical Polymerization Kinetics with Chain Length Dependent Termination... 

The chain length depends on the relative quantities of polymer and initiator that are used but also on the transfer frequency. The mass polydispersion of the produced polymer is always large. The lifetime of a radical varies from 10 1 to 10 seconds. The polymerization reaction stops spontaneously by deactivation. 

Bamer-Kowollik, C. Russell, G. T. Prog. Polym. Sci. 2009, in press ( Chain-length-dependent termination in radical polymerization Subtle revolution in tackling a long-standing challenge ). 

Polymeric species Living oligoradicals in The propagating radicals The polymer is at A chain-length-dependent... 

Unequal reactivity, that is chain-length dependent reactivity, is often important in high conversion free radical polymerization. However, this need not be considered here. 

The Importance of Chain-Length Dependent Kinetics in Free-Radical Polymerization A Preliminary Guide... 

Scope for Accessing the Chain Length Dependence of the Termination Rate Coefficient for Disparate Length Radicals in Acrylate Free Radical Polymerization... 

In what follows we will investigate whether such scaling laws exist and how important chain length dependent propagation is in free-radical polymerization. 

Based on an analysis of kinetic data on small radical additions and the first few propagation steps in free-radical polymerization, backed up by theoretical investigations of the propagation rate coefficient, we proposed the empirical formula given by Eq. 8 for the description of the chain-length dependence of the propagation rate coeffi-... 

In this paper we examined the effect of CLDP on kinetics in low-conversion free-radical polymerization. We have shown that although the chain length dependence of the individual fej, does not extend beyond for common systems, a significant macroscopic effect may be observed in systems with DPa up to 100. This observation leads us to draw some preliminary conclusions regarding CLDP (a) it should probably not be ignored in living radical polymerizations with low DPa ( 0>... 

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