The polymerization of methyl methacrylate in the presence of a variety of nitro compounds, containing one or more nitro groups, was found to yield polymers of decreased molecular weight. The chain transfer constants of these nitro solvents were determined from viscosity measurements of the resulting polymers using the relationship for the number-average degree of polymerization for unfractionated polymethyl methacrylate given by Baysal and Tobolsky [J. Polymer Sci. 9, 171 (1952)].
The chain transfer constants were found to increase with increasing nitro group content, varying from about 4 x 10-4 for mononitro compounds to about 1 for certain trinitro derivatives. Tetranitromethane inhibited the polymerization of methyl methacrylate.
Polynitro compounds were found to be powerful inhibitors in the polymerization of styrene and vinyl acetate even at low molar concentrations of the solvents.
The polymerization of trinitroethylmethacrylate was also investigated and was found to be unique inasmuch as a constant molecular weight of the homopolymer was obtained over a wide variation of initiator concentration and polymerization rate. Isopiestic molecular weight measurements showed the homopolymer had a degree of polymerization of 13 indicating a chain transfer constant for the trinitroethyl group of about 0'1.