Livingness

Following on from the above, various methods have been described to test and/or rank the livingness of polymerization processes." Ul7 20 All of these tests have limitations.. The following list paraphrases a set of criteria for living polymerization set out by Quirk and Lee11 who also critically assessed their applicability primarily in the context of living anionic polymerization. 

Therefore, livingness is validated by analyzing the linear conversion-time, conversion-molecular weight and conversion-iniferter concentration relationships. However, such an interpretation appears to be too simple to describe the whole process of iniferter-based radical polymerization, which is far more complex than expected. 

According to their recent reports [11], 5 provides livingness of polymerization for styrene (ST) and methyl methacrylic acid (MA). Irrespective of the type of monomer, the initiator efficiency / was over 0.9, and the polydis-persity index, Mw/Mn (Mw weight-average molecular weight, Mn number-average molecular weight), was close to unity (approximately 1.2). The polymerization rate was very low (on the order of an hour), i.e., a very slow... 

The polymerization of ethylene oxide (epoxyethane, EO) with 17 also proceeded by irradiation with visible light. For example, the polymerization with the mole ratio [EO]o/[17]o of 190 in benzene at room temperature, where the monomer conversion after 205 min was very low (<2%, determined by H NMR) in the dark, proceeded to 97% conversion in only 80 min under irradiation. The Mn of the polymer, as estimated from the GPC chromatogram, was 8700, which is in excellent agreement with the expected value of 8100 provided that the numbers of the molecules of the produced polymer and 17 (X=SPr) are equal [81]. The Mw/Mn of the polymer (1.05) was close to unity, indicating the livingness of the visible Hght induced polymerization of EO initiated with (NMTPP)ZnSPr (17). 

Keywords Telomerisation, fluoroalkene, telogen, free radical, livingness. 

Even if in 1955 Haszeldine [237] or in 1957 Hauptschein et al. [114,273] started to show a certain livingness of the radical telomerisation of CTFE with C1CF2CFC1I, the up to date research has attracted many academic or industrial chemists towards such a fascinating area. In addition, Dear and Gilbert [102] or Sharp et al. [84,103] performed the telomerisation of various fluoroolefins with disulfides but they did not examine the living character of this reaction. 

However, the step-wise cotelomerisation of fluoroalkenes has already shown original livingness, and the polymerisation via organometallic systems which is quite successful for hydrogenated monomers could be an encouraging route for these halogenated olefins. 

PaMeSt chain end] >10) before the addition of IB. This is based on a recent finding that the living cationic polymerization of pClaMeSt can be accomplished under conditions identical to those used for the synthesis of poly (aMeSt-fc-IB) copolymer [22, 23]. Importantly, the living PpClaMeSt chain end is very stable and there is no loss of livingness even after 5 h under monomer starved conditions. This is attributed to the reduced tendency of intramolecular alkylation due to the particularly large deactivating effect of the p-chloro substituent on the 2,5-positions of the aromatic ring. 

The first living systems based on anionic polymerization of nonpolar monomers, such as styrene and dienes in some hydrocarbon solvents, showed nearly perfect livingness producing very high molecular weight... 

It must be stressed that the observation of an increase in molecular weight with conversion should not be used as the only criterion of livingness. For example, termination alone will not affect a linear increase of molecular weights with conversion, because the number of chains will remain constant. However, termination leads to a rate reduction and additionally to a broadening of the MWD with conversion. Therefore, the combination of a linear increase in molecular weight with conversion and successful sequential monomer addition experiments, should be used to demonstrate the occurrence of controlled/living polymerizations. 

Cunningham and coworkers [65-68] have completed detailed modeling of nitroxide mediated radical polymerization in miniemulsion. They found that issues of distribution of the control agent between the aqueous and organic phases can be critical to maintaining livingness. 

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