Effective chain transfer

Bol shakov A.I., Barkalov I.M. Chain transfer effect in low-temperatures polymerizations of vinyl monomers at devitrification ethyl alcohol matrixes. Polymer Science, 23,1981, pp. 1086-1089. 

Note that any chain transfer effects of solvent arc included in the general term for transfer agent TH and that transfer to polymer is not included in this expression. 

C and 9.5 x 10 at 5 °C in cyclohexane [29]. Although chain transfer would be expected for p-methylstyrene, controlled polymerizations can be effected when the temperature is maintained at room temperature or below. The observations of broad molecular weight distributions and a low molecular weight tail by SEC analysis have provided evidence for chain transfer during the anionic polymerization of 7-isopropyl-a-methylstyrene [108]. Significant chain transfer effects have also been reported for alkyllithium-initiated polymerizations using alkenes as solvents [3]. 

While the various intervals in emulsion polymerization of VAc have a profound affect on the development of molar mass, other components added during the polymerization can also affect molar mass. Lee and Mallinson [21] determined that simple components such as surfactants can profoundly influence molar mass. They studied Aerosol OT [sodium bis-(2-ethylhexyl) sulfosuccinate] (AOT) and determined it can change the molar mass of a product by broadening the molar mass distribution. They reported an increase in polydispersity from 4.2-14 when AOT was substituted for sodium dodecyl sulfate in a VAc system. They attributed these results to significant chain transfer effects of AOT. 

Table III). This polymerization is apparently cationic, on the basis of the very rapid polymerization. The small amount of ether in the catalyst does not have a large chain transfer effect, as with BCMO, presumably because of the much higher base strength of DMO compared with BCMO and ether.

CTC with MA (see Table 10.15, Sec. 10.4) and by both a degradative and effective chain-transfer effect, systems with DMA present have enhanced amounts of MA in the copolymer. The DMA-MA CTC is capable of generating radicals and initiating free-radical polymerization of vinyl monomers. 

The molecular weights of PVC under monomer saturation conditions are nearly independent of conversion whereas under subsaturation pressures increases with conversion up to the total consumption of monomer. Under monomer saturated conditions the concentration of monomer at reaction loci is constant up to ca. 80% conversion. Here, the growth and termination events proceed under stable conditions (the constant monomer concentration and the chain transfer effect) at which the molecular weights are independent of conversion. As the polymerization proceeds at subsaturation pressures, the concentration of monomer decreases and the weight ratio monomer/polymer decreases and so does the growth of polymer chain. 

As a result of the chain transfer effects described, these initiators can function as telomerization initiators (115). Telomerization is a form of polymerization in which one molecule reacts to both initiate and terminate, or limit, the degree of polymerization of monomer. Thus, a species, XY, would initiate polymerization of a monomer, M, forming... 

Due to the chain transfer effect of some solvents where higher molecular weight polymers are required, the polymerisation is carried out at high solids content (80-85%) and diluted with further solvent when the polymerisation is completed. 

In conclusion, when the photoeured polymer is characterized by low mobility of the network (high Tg) the chain transfer effect, which induces a decrease of the crosslinking density (with a decrease of the glass transition temperature) is the main evidenced effect due... 

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