Columnar Assemblies of Aliphatic Poly(acetylene ester)s Prepared with a [Rh(norbornadiene)Cl]2 Catalyst.1H and13C NMR, X-Ray Diffraction and AFM Studies

Abstract

Alkyl propiolates: HC≡CCOOn-CmH2m+1(m = 2˜4), acetylene esters were polymerized with a [Rh(norbornadiene)Cl]2 catalyst in methanol as the polymerization solvent to produce poly(n-alkyl propiolate)s, PAPAs, called polyacetylene esters, in relatively high yields. The resulting PAPAs were characterized in detail using 1H and 13C NMR spectroscopy, X-ray diffraction, and atomic force microscope methods. The data showed that the resulting polymers selectively have cis-transoid form. The cis-transoid isomer is not amorphous but holds a pseudohexagonal structure called a columnar assembly the diameter of which agrees with those estimated by the semiempirical calculation method (AM1). The crystalline ratios of the columnar assemblies were also estimated to be ca. 60 ˜ 70%. In the case of poly(ethyl propiolate), PEPA, the crystalline size was found to approximately agree with that estimated from the AFM images of the cast film of PEPA.