Geometrical structures of poly(haloalkyl propiolate)s prepared with a [Rh(norbornadiene)Cl]2 catalyst

The polymerization of ω-haloalkyl propiolates initiated by [Rh(norbornadiene)Cl]2 in methanol has been investigated in detail together with the geometrical forms of the resulting polymers. The polymer yield and molecular weight of poly(2-haloethyl propiolate)s (P(2XEPA)s) were markedly reduced in the order of X = Cl, Br, and I. 1H NMR, electron spin resonance, and diffuse reflective UV-vis spectroscopic studies of P(2XEPA)s revealed that the content of cis form regarding the CC was markedly decreased from 60% for P(2ClEPA) to 15% for P(2IEPA). The decrease in the cis content also resulted in notable reduction of the crystallinity of the polymer from 30% for P(2ClEPA) to less than 10% for P(2IEPA). Compression of P(2XEPA)s at room temperature induced the so-called cis-to-trans isomerization accompanied with decomposition of the polymers.