Polymers from 1,2-Disubstituted Ethylenic Monomers. V. Radical Polymerization of Dimethyl Maleate in the Presence or Absence of Isomerization Catalyst

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Abstract
Although dimethyl maleate (DMM) did not give any homopolymer with a radical initiator, it was polymerized in the presence of some amines via a monomer-isomerization radical polymerization mechanism, i.e., DMM isomerized to dimethyl fumarate (DMF) which then homopolymerized. For this polymerization, some primary or secondary aliphatic amines served as isomerization catalysts, and morpholine showed the most efficient activity. The activation energies for the monomer-isomerization radical polymerization of DMM with di-tert-butyl peroxide in the presence of morpholine and for the isomerization from DMM to DMF with morpholine were 95.9 and 23.0 kJ/mol, respectively. Morpholine was also observed to act as a retarder in radical polymerization of DMF. Moreover, the relationships between rates or copolymer compositions and the feed monomer compositions in the copolymerization of DMM with styrene in the presence of morpholine were found to become close to those of DMF with styrene, although both relationships were different in the absence of morpholine.