Homopolymerization of PEO Macromonomers

Gramain and Frere [82] observed that the free radical polymerization of co-meth-acryloyl terminated PEO macromonomers in the aqueous phase deviates from the solution polymerization. Polymerizations initiated by KPS in water were much faster than those that proceeded in the solution. Low molecular weight polymers were formed in the aqueous systems (ca. up to 20 macromonomer units were incorporated into polymer molecules). 

The square-root dependence of [AVA] supports the conventional (instantaneous) bimolecular termination of the growing radicals and/or the higher nuclea-tion activity of the present system compared to the micellar model [9,10]. The high rate of polymerization resembles the polymerization in particles and was discussed in terms of the micellar polymerization considering that the kt was extremely low. The linear dependence of Rp on the macromonomer concentration (the first-order dependence of [tC4-(EO)24-MA] or [tC4-(EO)24-VB]) was attributed to the linear dependence of the number of micelles on the macromonomer 

Similarly, the rate of polymerization of PEO-MA macromonomers was found to increase with increasing hydrophobicity around the MA end group in the order [71 ] 

This result supports the micellar polymerization mechanism, i.e., the stronger hydrophobic intermolecular interactions between PEO molecules favors the 

The higher the hydrophilicity of macromonomer, the lower the final conversion. This may be attributed to the formation of hydrophilic or surface active oligomer radicals and the low or high radical entry rate. In the system with hydrophilic C1-(EO)17-MA, the limiting conversion was ca. 60%. Thus the low rate of polymerization at ca. 50 or 60% conversion may be discussed in terms of the solution polymerization, a strong bimolecular termination and the low radical entry rate. 

---