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E. Witek, A. Kochanowski, S. Kudła, E. Bortel



Attempts at living polymerization in aqueous solutions


Polimery 1998, No 7-8, 437


DOI: dx.doi.org/10.14314/polimery.1998.437


Summary

Radical polymerizations of aqueous acrylic acid initiated with ammonium peroxydisulfate were carried out in the presence of various mediators: (i) NaNO2 and (ii) 4 -amino-2 ,2 ,6 ,6 -tetramethyl-1-piperidinoxyl (ATEMPO) radical. Possible occurrence of pseudo-living polymerization was examined in either case. At temperatures lower than 60°C, polymerization was found to have been retarded in series (i) and (ii). At 90°C, conversion (a) was 70—80% in a polymerization time (t) of 125—185 min. The radicals NO and NO2 generated by NaNO2 in reaction (7) failed to_ensure a pseudoliving polymerization to occur. Polydispersities D (= Mw /Mn), 6.5—9.6, were too high for such a process. With ATEMPO, some traits of pseudo-living polymerization became visible, viz., D = 1.21 or 1.28, much lower than the 9.81 for non-mediated poly(acrylic acid). The NaNO2-mediated polymerization of acrylic acid in an aqueous solution at pH = 7 is characterized by the absence of the Trommsdorf (gel) effect which enables concentrations as high as 40 g/dL to be used.


Keywords: poly(acrylic acid), „living" radical polymerization in aqueous solutions, mediators, polymerization rate, coefficient of polydispersity


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