Dilute solution properties of cyclized polybutadiene.

Yamamoto Kazuhiko, Bessho Nobuo, Shiibashi Toru, Maekawa Etsuji

doi:10.1295/polymj.13.555

Light scattering and viscosity measurements on dilute solutions of cyclized cis-1,4-polybutadiene polymers (CBR) with different degrees of cyclization (DC) and their fractions are reported in this paper. The data were obtained in both cyclohexane and mixed theta solvents at 30.0°C. The curves of the intrinsic viscosity [η]₀ in mixed theta solvents vs. the weight average molecular weight M_w for CBR with DC over 30% exhibited two distinct regions with slopes of 0.5 and less. Thus, the exponent in the viscosity equation is the same as that for the original uncyclized samples at M_w below the critical point M_wc and decrease with increasing DC at M_w above M_wc. The M_wc shifts to lower M_w as DC is increased. The relation of the molecular structure of CBR with DC is discussed. The results led to the conclusions that 1) at DC below 25%, the molecules are linear in the overall structure, but locally contain short intramolecular cyclic structures, e.g., mono- and/or bicyclic structures, 2) at DC between 25 and 60%, the molecules are randomly branched, and 3) at DC over 80%, the molecules have probably very compact structure formed by internal crosslinks.

Dilute solution properties of cyclized polybutadiene.

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