Chain transfer agent, thiol acts

In mbber production, the thiol acts as a chain transfer agent, in which it functions as a hydrogen atom donor to one mbber chain, effectively finishing chain growth for that polymer chain. The sulfur-based radical then either terminates with another radical species or initiates another chain. The thiol is used up in this process. The length of the mbber polymer chain is a function of the thiol concentration. The higher the concentration, the shorter the mbber chain and the softer the mbber. An array of thiols have subsequendy been utilized in the production of many different polymers. Some of these apphcations are as foUow ... 

In both recipes, the thiol acts as a chain transfer agent to prevent the molecular weight from attaining the excessively high values possible in emulsion polymerization systems (see Table 2.6). It acts in an analogous fashion to the solvent... 

Radical chain hydrosilylation of alkenes using RsSiH, where R = alkyl and/ or phenyl, is not very useful in synthesis because the hydrogen abstraction step is slow under standard experimental conditions (cf. Section 3.1). These reactions proceed under drastic conditions (Reaction 5.9) [3], but can be promoted under milder conditions by the presence of catalytic amounts of a thiol [27]. Thus, the propagation steps in Scheme 5.1 are replaced by those reported in Scheme 5.4, where the thiol acts as the catalyst and the H transfer agent (see Iso Section 4.5). 

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