Telogens functional

The initiator A is not necessarily functional, but in this case, the telogen is difunctional or may be potentially functional G—T—T—G... 

The first two methods deal with the telomerization of a non-functional monomer with a functional telogen (first method) or a telogen which can lx further modified in order to exhibit the functional group (second method). 

The two last methods consist of performing the monoaddition on. both sides of the chain extremity of a non-conjugated diene (third method) with a functional telogen or on a telogen with a functional monomers (four method). We are going to study each of these methods. 

Few studies on acid disulfides have been performed, whatever the functionality of these telogens. Tables 13 and 14 sum up their basic transfer constants to MMA and Styrene. 

First several authors planned their use as initiators for thermal or photochemical polymerization for different monomers. Thus, Otsu [55] compared the activity of these xanthogens, sulfides, disulfides and thiuram with several monomers — MMA, S., A.N., VAc, VDC. The results allowed him to classify products as telogens and not as functional initiators. In the same way, these surveys showed that they are photoinitiators without having retarding or inhibiting effects as are observed for several disulfides. 

Several non-conjugated dienes can react in a double addition with functional telogen as we note in Table 17. 

Table 17. Possible telomerization of non-conjugated dienes with functional telogens...

We studied the bistelomerization of various functional monomers with these a,co-ditrichloromethyl telogens and the results have been summed up in Table 18. 

As has been mentioned, radical initiation has greatly contributed to iJie search for new telechelic polymers either by the u of functional initiators or by telomerization. In both cases, besides the methods known from 1955, recent surveys have been investigated and, several applications have been found. However, such reactions require, from the synthetic point of view, the obtaining of new initiators and telogens and from the kinetical point of view, vay selective reactives which have a very high reactivity (great transfer constant rralue). 

In the case of these complex zinc hexacyanocobaltate initiators, the telogen could be a diol such as propylene glycol, a triol such as glycerine, or a higher functionality polyol such as pentaerythritol or sorbitol, and the product could then be a polyol of the type used extensively in making polyurethanes in elastomeric, foam, or... 

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