Diethyl fumarate/maleate, radical polymerization

As background information, an attempt was made to copolymerize cis-2-butene-l,4-diol diacetate with MA. Heating equimolar mixtures of the two monomers with AIBN (2 wt%) for 15 hr. at 75°C produced only a very low yield (<10%) of polymeric material. Using the same conditions, equimolar mixtures of IA-di-t-butyl fumarate and IA-dimethyl maleate gave only a trace of copolymer. Yokayama and Hall (10) also repored that diethyl maleate and diethyl fumarate undergo free-radical copolymerization with IA to give very low yields of non-equimolar copolymer. 

Homopolymerizatiqns of diethyl fiimarate by a free-radical mechanism were reported. The Mn was found to be 15,000. The same is true of homopolymerizations of several other dialkyl fumarates and also dialkyl maleates. The polymerization rates and the sizes of the polymers that form decrease with increases in the lengths of linear alkyl ester groups. There is, however, an opposite correlation if the ester groups are branched. Also, the maleate esters appear to isomerize to fumarates prior to polymerization. "... 

Because Pd complexes would catalyze dimerization of EDA to give diethyl fu-marate and maleate, it might be possible that the polymers were obtained by radical polymerization of the diesters generated by the Pd-catalyzed dimerization. However, whereas the polymer obtained by AIBN-initiated radical polymerization of diethyl fumarate exhibited signals in MALDI-TOF-MS spectra with peak intervals of m/z = 172 (CHC02Et x 2), the intervals of the spectra of polymers from EDA were m/z = 86, suggesting that the polymers were not obtained by the radical polymerization of the diesters [38] (Scheme 15). 

Scheme 15 Radical polymerization of diethyl fumarate and maleate vs. PdCL-mediated polymerization of ethyl diazoacetate...

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