Effect of polyfunctional chain transfer agents on the molecular weight distribution in free‐radical polymerization, 3 Polymerization of methyl methacrylate in the presence of polyfunctional chain transfer agents

Abstract

Polymerization of methyl methacrylate was carried out in the presence of polyfunctional chain transfer agents: 1,6‐hexanedithiol, trimethylolpropane^b tris(mercaptoglycolate) and pentaerythritol tetrakis(3‐mercaptopropionate). The theoretical results reported in the preceding papers are completely confirmed: the experimental values of the dispersion index (D = M̄_w/M̄_n) are 1.62 for f = 2, 1.39 for f = 3 and 1.28 for f = 4. In the case of bifunctional transfer agents the molecular weights calculated are in very good agreement with those obtained by size exclusion chromatography. The formation of star‐shaped macromolecules was confirmed by cleavage of the CSC bonds. The number‐average molecular weight decreases and the dispersion index is approximately equal to 2 after exposure to UV rays. The phenomenon of “pseudo‐living” polymerization in the presence of polyfunctional chain transfer agents is also discussed.