Propagation, chain-length dependent

Keywords chain-length dependent propagation chain-length dependent termination ... 

Chain Length Dependence of Propagation Rate Constants... 

The parameters indexed with a are connected with the nucleation step or other effects occurring only once per triple helix. Parameters denoted by s are related with the equilibrium constants of the propagation steps and are ordered to be independent of the position of the reacting chain segment. This implies that end effects are neglected. Since the same dependences are valid for AH° and AS, with the help of their chain length dependence we can determine AG by extrapolation up to 3 n - 2 = 0, and thus, a can be estimated it depends neither on temperature nor on the chain length. 

Olaj et al. (27) rekindled interest in the issue of chain-length-dependent propagation (CLDP), an issue that Hants and coworkers have pursued most recently 28-31). CLDP results in veiy small radicals growing relatively quickly 28), and thus - opposite to CLDT - it causes narrowing of a MWD 29). The effect can be substantial, with PDl of 1.5 having been observed for transfer-controlled systems withDPn- 15 30), as opposed to the classical kinetics value... 

The chain length dependence of termination rate constants (Section 5.2.1.4) should not be ignored when considering copolymerization kinetics. It has been pointed out that average chain lengths in copolymerization will be a function of the monomer feed composition especially in copolymerizations with disparate propagation rate constants. Factors determining the rate of copolymerizalion are not fully resolved and copolymerization kinetics remains a topic of discussion and an area in need of further study. 

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

In the third one, chain-length dependence of the propagation rates was measured in polymerizations of methyl methacrylate. In the range of DPs from 130-14,200 the propagation constant was shown to be independent of the chain length. ... 

The chain-length dependence of the propagation rate coefficient is of a more chemical nature in that it is caused by differences in the activation energy and the frequency factor of the actual, intrinsic, rate coefficients of the addition reaction for different size radicals. chain-length averaged propagation rate coefficient is defined by Eq. 4,... 

So, where does this leave the experimental polymer chemist Is detailed knowledge really required about kp, k / and the distribution of R Those familiar with the literature regarding chain-length dependent termination (and now also chain-length dependent propagation) have probably encountered unfriendly looking math-... 

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

Chain-Length Dependent Termination and Propagation Rate Coefficients... 

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-... 

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