Generation in situ of NAD by Grafting Reactions

In order to improve the chain transfer reaction with the polyether chains, a quantity of polyethers, having chemical groups which give very high transfer reaction rates such as -SH [35, 36], -S-S- [35, 36] or tertiary amine groups [37], were used in the mixture with polyethers used for grafting reactions. 

The radical generated at the sulfur atom initiates a new polymeric carbocatenary chain  

The resulting structure (6.7) is in fact a very efficient NAD obtained in situ by transfer reactions with terminal -SH groups [35, 36]. 

The polyether polyols, initiated by triethanolamine or by the ethylene diamine with a molecular weight of 3000-7000 daltons, are polyethers having a tertiary amine structure with a high capability to give transfer reactions [37, 39]  

The structure (6.8) is another type of NAD formed in situ by transfer reaction with the tertiary amine type polyethers. Addition of a high molecular weight polyether initiated by an alkanolamine, ethylene diamine, N-methyl substituted propylene diamine, or N,N dimethyl dipropylene diamines in the polyether polyol used for grafting leads to the formation of very stable polymeric dispersions [37]. The solid fraction has particles of low median diameter ( 1.5 pm). The resulting polymer polyols have low viscosities which give good stabilisation of the polymeric dispersion. 

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