synopsisThe anionic p,olymerization of a variety of secondary alkyl crotonates and related monomers initiated by fluorenyllithium (complexed with tetrahydrofuran) in toluene a t -78°C. is reported. No crystallinity could be developed in any of the samples, and nuclear magnetic resonance was uninformative about possible tacticity. The polymerization techniques were ineffective when applied to n-alkyl esters. Polymer was obtained from isopropyl cinnamate and N,N-dimethyl crotonamide, but not from isopropyl thiocrotonate or isopropyl Zpentenoate. The physical properties of injectionmolded specimens of polymers of isopropyl, s-butyl and cyclohexyl crotonate were examined in some detail; the polymers exhibited a desirable combination of high service temperatures and good impact resistance for a vinyl homopolymer but were extremely difficult to mold. Poly(isopropy1 crotonate) had a heat distortion temperature of 125OC. at 85 psi, a notched h o d impact of 2.4 ft.-lb./in. of notch, and a flexural modulus of 274,000 psi.Intense interest in the stereoregular anionic polymerization of acrylic and methacrylic esters during the past ten years has led several investigators to examine the polymerization of related a,@-unsaturated esters with substituents other than hydrogen on the @ carbon atom of the double bond, the simplest of these systems being esters of crotonic acid. Miller and Skogman' have reported studies of the polymerization of t-butyl crotonate; they showed that there were limitations on the nature of the anionic initiator that could be employed, both in the ability to initiate polymerization and in the degree of crystallinity of the polymer formed. No physical properties of the polymer were reported other than a glass transition temperature of 86°C. Natta et a1.2 have disclosed the preparation of crystalline poly(t-butyl crotonate) and poly(isopropy1 crotonate), the latter softening at 27O-29O0C., by polymerization in toluene at -78°C. with ether-free phenylmagnesium bromide as initiator.Since the completion of our experimental program Makimoto, Tanabe, and Tsuruta have reported the polymerization of methyl crotonate with calcium zinctetraethyl complex in toluene and have stated that this
