CONFORMATIONAL CHARACTERISTICS OF SOME MODEL POLYDIENES AND POLYOLEFINS

The conformational behavior of model polydienes and their saturated polyolefinic analogues has been studied. The polymers were based on 1,3-butadiene, 2,3-dimethylbutadiene, 2-ethyl-1,3-butadiene, and 3-methylene-7-methyl-1,6-octadiene (beta-myrcene). The unperturbed chain dimensions of these near-monodisperse polymers were evaluated under THETA or near-THETA conditions via intrinsic viscosity measurements. Consequently, information was obtained regarding the influence of side-chain length on chain dimensions as well as the influence of head-to-head structures in polypropylene. The temperature coefficient (d ln <R2>0/dT) for chain dimensions of alternating poly(ethylene-butene) was determined. Its value of -0.9 x 10(-3) K-1 is in consonance with the values for polyethylene and alternating poly(ethylene-propylene). The temperature coefficients for poly(vinylethylene), a butene-rich poly(ethylene-butene) material, and poly(ethylethylene) were also measured. The value for the latter polymer is notably larger (-2.3 x 10(-3) K-1) than that predicted (-0.1 x 10(-3) K-1) from the five-state rotational isomeric state model. A value of -1.7 x 10(-3) K-1 was measured for poly(vinylethylene), while -1.4 x 10(-3) K-1 was found for a butene-rich poly(ethylene-butene) copolymer (40 ethyl branches per 100 backbone carbons).